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  • The Incremental Architect&acute;s Napkin - #2 - Balancing the forces

    - by Ralf Westphal
    Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/06/02/the-incremental-architectacutes-napkin---2---balancing-the-forces.aspxCategorizing requirements is the prerequisite for ecconomic architectural decisions. Not all requirements are created equal. However, to truely understand and describe the requirement forces pulling on software development, I think further examination of the requirements aspects is varranted. Aspects of Functionality There are two sides to Functionality requirements. It´s about what a software should do. I call that the Operations it implements. Operations are defined by expressions and control structures or calls to frameworks of some sort, i.e. (business) logic statements. Operations calculate, transform, aggregate, validate, send, receive, load, store etc. Operations are about behavior; they take input and produce output by considering state. I´m not using the term “function” here, because functions - or methods or sub-programs - are not necessary to implement Operations. Functions belong to a different sub-aspect of requirements (see below). Operations alone are not enough, though, to make a customer happy with regard to his/her Functionality requirements. Only correctly implemented Operations provide full value. This should make clear, why testing is so important. And not just manual tests during development of some operational feature, but automated tests. Because only automated tests scale when over time the number of operations increases. Without automated tests there is no guarantee formerly correct operations are still correct after more got added. To retest all previous operations manually is infeasible. So whoever relies just on manual tests is not really balancing the two forces Operations and Correctness. With manual tests more weight is put on the side of the scale of Operations. That might be ok for a short period of time - but in the long run it will bite you. You need to plan for Correctness in the long run from the first day of your project on. Aspects of Quality As important as Functionality is, it´s not the driver for software development. No software has ever been written to just implement some operation in code. We don´t need computers just to do something. All computers can do with software we can do without them. Well, at least given enough time and resources. We could calculate the most complex formulas without computers. We could do auctions with millions of people without computers. The only reason we want computers to help us with this and a million other Operations is… We don´t want to wait for the results very long. Or we want less errors. Or we want easier accessability to complicated solutions. So the main reason for customers to buy/order software is some Quality. They want some Functionality with a higher Quality (e.g. performance, scalability, usability, security…) than without the software. But Qualities come in at least two flavors: Most important are Primary Qualities. That´s the Qualities software truely is written for. Take an online auction website for example. Its Primary Qualities are performance, scalability, and usability, I´d say. Auctions should come within reach of millions of people; setting up an auction should be very easy; finding a suitable auction and bidding on it should be as fast as possible. Only if those Qualities have been implemented does security become relevant. A secure auction website is important - but not as important as a fast auction website. Nobody would want to use the most secure auction website if it was unbearably slow. But there would be people willing to use the fastest auction website even it was lacking security. That´s why security - with regard to online auction software - is not a Primary Quality, but just a Secondary Quality. It´s a supporting quality, so to speak. It does not deliver value by itself. With a password manager software this might be different. There security might be a Primary Quality. Please get me right: I don´t want to denigrate any Quality. There´s a long list of non-functional requirements at Wikipedia. They are all created equal - but that does not mean they are equally important for all software projects. When confronted with Quality requirements check with the customer which are primary and which are secondary. That will help to make good economical decisions when in a crunch. Resources are always limited - but requirements are a bottomless ocean. Aspects of Security of Investment Functionality and Quality are traditionally the requirement aspects cared for most - by customers and developers alike. Even today, when pressure rises in a project, tunnel vision will focus on them. Any measures to create and hold up Security of Investment (SoI) will be out of the window pretty quickly. Resistance to customers and/or management is futile. As long as SoI is not placed on equal footing with Functionality and Quality it´s bound to suffer under pressure. To look closer at what SoI means will help to become more conscious about it and make customers and management aware of the risks of neglecting it. SoI to me has two facets: Production Efficiency (PE) is about speed of delivering value. Customers like short response times. Short response times mean less money spent. So whatever makes software development faster supports this requirement. This must not lead to duct tape programming and banging out features by the dozen, though. Because customers don´t just want Operations and Quality, but also Correctness. So if Correctness gets compromised by focussing too much on Production Efficiency it will fire back. Customers want PE not just today, but over the whole course of a software´s lifecycle. That means, it´s not just about coding speed, but equally about code quality. If code quality leads to rework the PE is on an unsatisfactory level. Also if code production leads to waste it´s unsatisfactory. Because the effort which went into waste could have been used to produce value. Rework and waste cost money. Rework and waste abound, however, as long as PE is not addressed explicitly with management and customers. Thanks to the Agile and Lean movements that´s increasingly the case. Nevertheless more could and should be done in many teams. Each and every developer should keep in mind that Production Efficiency is as important to the customer as Functionality and Quality - whether he/she states it or not. Making software development more efficient is important - but still sooner or later even agile projects are going to hit a glas ceiling. At least as long as they neglect the second SoI facet: Evolvability. Delivering correct high quality functionality in short cycles today is good. But not just any software structure will allow this to happen for an indefinite amount of time.[1] The less explicitly software was designed the sooner it´s going to get stuck. Big ball of mud, monolith, brownfield, legacy code, technical debt… there are many names for software structures that have lost the ability to evolve, to be easily changed to accomodate new requirements. An evolvable code base is the opposite of a brownfield. It´s code which can be easily understood (by developers with sufficient domain expertise) and then easily changed to accomodate new requirements. Ideally the costs of adding feature X to an evolvable code base is independent of when it is requested - or at least the costs should only increase linearly, not exponentially.[2] Clean Code, Agile Architecture, and even traditional Software Engineering are concerned with Evolvability. However, it seems no systematic way of achieving it has been layed out yet. TDD + SOLID help - but still… When I look at the design ability reality in teams I see much room for improvement. As stated previously, SoI - or to be more precise: Evolvability - can hardly be measured. Plus the customer rarely states an explicit expectation with regard to it. That´s why I think, special care must be taken to not neglect it. Postponing it to some large refactorings should not be an option. Rather Evolvability needs to be a core concern for every single developer day. This should not mean Evolvability is more important than any of the other requirement aspects. But neither is it less important. That´s why more effort needs to be invested into it, to bring it on par with the other aspects, which usually are much more in focus. In closing As you see, requirements are of quite different kinds. To not take that into account will make it harder to understand the customer, and to make economic decisions. Those sub-aspects of requirements are forces pulling in different directions. To improve performance might have an impact on Evolvability. To increase Production Efficiency might have an impact on security etc. No requirement aspect should go unchecked when deciding how to allocate resources. Balancing should be explicit. And it should be possible to trace back each decision to a requirement. Why is there a null-check on parameters at the start of the method? Why are there 5000 LOC in this method? Why are there interfaces on those classes? Why is this functionality running on the threadpool? Why is this function defined on that class? Why is this class depending on three other classes? These and a thousand more questions are not to mean anything should be different in a code base. But it´s important to know the reason behind all of these decisions. Because not knowing the reason possibly means waste and having decided suboptimally. And how do we ensure to balance all requirement aspects? That needs practices and transparency. Practices means doing things a certain way and not another, even though that might be possible. We´re dealing with dangerous tools here. Like a knife is a dangerous tool. Harm can be done if we use our tools in just any way at the whim of the moment. Over the centuries rules and practices have been established how to use knifes. You don´t put them in peoples´ legs just because you´re feeling like it. You hand over a knife with the handle towards the receiver. You might not even be allowed to cut round food like potatos or eggs with it. The same should be the case for dangerous tools like object-orientation, remote communication, threads etc. We need practices to use them in a way so requirements are balanced almost automatically. In addition, to be able to work on software as a team we need transparency. We need means to share our thoughts, to work jointly on mental models. So far our tools are focused on working with code. Testing frameworks, build servers, DI containers, intellisense, refactoring support… That´s all nice and well. I don´t want to miss any of that. But I think it´s not enough. We´re missing mental tools, tools for making thinking and talking about software (independently of code) easier. You might think, enough of such tools already exist like all those UML diagram types or Flow Charts. But then, isn´t it strange, hardly any team is using them to design software? Or is that just due to a lack of education? I don´t think so. It´s a matter value/weight ratio: the current mental tools are too heavy weight compared to the value they deliver. So my conclusion is, we need lightweight tools to really be able to balance requirements. Software development is complex. We need guidance not to forget important aspects. That´s like with flying an airplane. Pilots don´t just jump in and take off for their destination. Yes, there are times when they are “flying by the seats of their pants”, when they are just experts doing thing intuitively. But most of the time they are going through honed practices called checklist. See “The Checklist Manifesto” for very enlightening details on this. Maybe then I should say it like this: We need more checklists for the complex businss of software development.[3] But that´s what software development mostly is about: changing software over an unknown period of time. It needs to be corrected in order to finally provide promised operations. It needs to be enhanced to provide ever more operations and qualities. All this without knowing when it´s going to stop. Probably never - until “maintainability” hits a wall when the technical debt is too large, the brownfield too deep. Software development is not a sprint, is not a marathon, not even an ultra marathon. Because to all this there is a foreseeable end. Software development is like continuously and foreever running… ? And sometimes I dare to think that costs could even decrease over time. Think of it: With each feature a software becomes richer in functionality. So with each additional feature the chance of there being already functionality helping its implementation increases. That should lead to less costs of feature X if it´s requested later than sooner. X requested later could stand on the shoulders of previous features. Alas, reality seems to be far from this despite 20+ years of admonishing developers to think in terms of reusability.[1] ? Please don´t get me wrong: I don´t want to bog down the “art” of software development with heavyweight practices and heaps of rules to follow. The framework we need should be lightweight. It should not stand in the way of delivering value to the customer. It´s purpose is even to make that easier by helping us to focus and decreasing waste and rework. ?

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  • How to simulate inner join on very large files in java (without running out of memory)

    - by Constantin
    I am trying to simulate SQL joins using java and very large text files (INNER, RIGHT OUTER and LEFT OUTER). The files have already been sorted using an external sort routine. The issue I have is I am trying to find the most efficient way to deal with the INNER join part of the algorithm. Right now I am using two Lists to store the lines that have the same key and iterate through the set of lines in the right file once for every line in the left file (provided the keys still match). In other words, the join key is not unique in each file so would need to account for the Cartesian product situations ... left_01, 1 left_02, 1 right_01, 1 right_02, 1 right_03, 1 left_01 joins to right_01 using key 1 left_01 joins to right_02 using key 1 left_01 joins to right_03 using key 1 left_02 joins to right_01 using key 1 left_02 joins to right_02 using key 1 left_02 joins to right_03 using key 1 My concern is one of memory. I will run out of memory if i use the approach below but still want the inner join part to work fairly quickly. What is the best approach to deal with the INNER join part keeping in mind that these files may potentially be huge public class Joiner { private void join(BufferedReader left, BufferedReader right, BufferedWriter output) throws Throwable { BufferedReader _left = left; BufferedReader _right = right; BufferedWriter _output = output; Record _leftRecord; Record _rightRecord; _leftRecord = read(_left); _rightRecord = read(_right); while( _leftRecord != null && _rightRecord != null ) { if( _leftRecord.getKey() < _rightRecord.getKey() ) { write(_output, _leftRecord, null); _leftRecord = read(_left); } else if( _leftRecord.getKey() > _rightRecord.getKey() ) { write(_output, null, _rightRecord); _rightRecord = read(_right); } else { List<Record> leftList = new ArrayList<Record>(); List<Record> rightList = new ArrayList<Record>(); _leftRecord = readRecords(leftList, _leftRecord, _left); _rightRecord = readRecords(rightList, _rightRecord, _right); for( Record equalKeyLeftRecord : leftList ){ for( Record equalKeyRightRecord : rightList ){ write(_output, equalKeyLeftRecord, equalKeyRightRecord); } } } } if( _leftRecord != null ) { write(_output, _leftRecord, null); _leftRecord = read(_left); while(_leftRecord != null) { write(_output, _leftRecord, null); _leftRecord = read(_left); } } else { if( _rightRecord != null ) { write(_output, null, _rightRecord); _rightRecord = read(_right); while(_rightRecord != null) { write(_output, null, _rightRecord); _rightRecord = read(_right); } } } _left.close(); _right.close(); _output.flush(); _output.close(); } private Record read(BufferedReader reader) throws Throwable { Record record = null; String data = reader.readLine(); if( data != null ) { record = new Record(data.split("\t")); } return record; } private Record readRecords(List<Record> list, Record record, BufferedReader reader) throws Throwable { int key = record.getKey(); list.add(record); record = read(reader); while( record != null && record.getKey() == key) { list.add(record); record = read(reader); } return record; } private void write(BufferedWriter writer, Record left, Record right) throws Throwable { String leftKey = (left == null ? "null" : Integer.toString(left.getKey())); String leftData = (left == null ? "null" : left.getData()); String rightKey = (right == null ? "null" : Integer.toString(right.getKey())); String rightData = (right == null ? "null" : right.getData()); writer.write("[" + leftKey + "][" + leftData + "][" + rightKey + "][" + rightData + "]\n"); } public static void main(String[] args) { try { BufferedReader leftReader = new BufferedReader(new FileReader("LEFT.DAT")); BufferedReader rightReader = new BufferedReader(new FileReader("RIGHT.DAT")); BufferedWriter output = new BufferedWriter(new FileWriter("OUTPUT.DAT")); Joiner joiner = new Joiner(); joiner.join(leftReader, rightReader, output); } catch (Throwable e) { e.printStackTrace(); } } } After applying the ideas from the proposed answer, I changed the loop to this private void join(RandomAccessFile left, RandomAccessFile right, BufferedWriter output) throws Throwable { long _pointer = 0; RandomAccessFile _left = left; RandomAccessFile _right = right; BufferedWriter _output = output; Record _leftRecord; Record _rightRecord; _leftRecord = read(_left); _rightRecord = read(_right); while( _leftRecord != null && _rightRecord != null ) { if( _leftRecord.getKey() < _rightRecord.getKey() ) { write(_output, _leftRecord, null); _leftRecord = read(_left); } else if( _leftRecord.getKey() > _rightRecord.getKey() ) { write(_output, null, _rightRecord); _pointer = _right.getFilePointer(); _rightRecord = read(_right); } else { long _tempPointer = 0; int key = _leftRecord.getKey(); while( _leftRecord != null && _leftRecord.getKey() == key ) { _right.seek(_pointer); _rightRecord = read(_right); while( _rightRecord != null && _rightRecord.getKey() == key ) { write(_output, _leftRecord, _rightRecord ); _tempPointer = _right.getFilePointer(); _rightRecord = read(_right); } _leftRecord = read(_left); } _pointer = _tempPointer; } } if( _leftRecord != null ) { write(_output, _leftRecord, null); _leftRecord = read(_left); while(_leftRecord != null) { write(_output, _leftRecord, null); _leftRecord = read(_left); } } else { if( _rightRecord != null ) { write(_output, null, _rightRecord); _rightRecord = read(_right); while(_rightRecord != null) { write(_output, null, _rightRecord); _rightRecord = read(_right); } } } _left.close(); _right.close(); _output.flush(); _output.close(); } UPDATE While this approach worked, it was terribly slow and so I have modified this to create files as buffers and this works very well. Here is the update ... private long getMaxBufferedLines(File file) throws Throwable { long freeBytes = Runtime.getRuntime().freeMemory() / 2; return (freeBytes / (file.length() / getLineCount(file))); } private void join(File left, File right, File output, JoinType joinType) throws Throwable { BufferedReader leftFile = new BufferedReader(new FileReader(left)); BufferedReader rightFile = new BufferedReader(new FileReader(right)); BufferedWriter outputFile = new BufferedWriter(new FileWriter(output)); long maxBufferedLines = getMaxBufferedLines(right); Record leftRecord; Record rightRecord; leftRecord = read(leftFile); rightRecord = read(rightFile); while( leftRecord != null && rightRecord != null ) { if( leftRecord.getKey().compareTo(rightRecord.getKey()) < 0) { if( joinType == JoinType.LeftOuterJoin || joinType == JoinType.LeftExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, leftRecord, null); } leftRecord = read(leftFile); } else if( leftRecord.getKey().compareTo(rightRecord.getKey()) > 0 ) { if( joinType == JoinType.RightOuterJoin || joinType == JoinType.RightExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, null, rightRecord); } rightRecord = read(rightFile); } else if( leftRecord.getKey().compareTo(rightRecord.getKey()) == 0 ) { String key = leftRecord.getKey(); List<File> rightRecordFileList = new ArrayList<File>(); List<Record> rightRecordList = new ArrayList<Record>(); rightRecordList.add(rightRecord); rightRecord = consume(key, rightFile, rightRecordList, rightRecordFileList, maxBufferedLines); while( leftRecord != null && leftRecord.getKey().compareTo(key) == 0 ) { processRightRecords(outputFile, leftRecord, rightRecordFileList, rightRecordList, joinType); leftRecord = read(leftFile); } // need a dispose for deleting files in list } else { throw new Exception("DATA IS NOT SORTED"); } } if( leftRecord != null ) { if( joinType == JoinType.LeftOuterJoin || joinType == JoinType.LeftExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, leftRecord, null); } leftRecord = read(leftFile); while(leftRecord != null) { if( joinType == JoinType.LeftOuterJoin || joinType == JoinType.LeftExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, leftRecord, null); } leftRecord = read(leftFile); } } else { if( rightRecord != null ) { if( joinType == JoinType.RightOuterJoin || joinType == JoinType.RightExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, null, rightRecord); } rightRecord = read(rightFile); while(rightRecord != null) { if( joinType == JoinType.RightOuterJoin || joinType == JoinType.RightExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, null, rightRecord); } rightRecord = read(rightFile); } } } leftFile.close(); rightFile.close(); outputFile.flush(); outputFile.close(); } public void processRightRecords(BufferedWriter outputFile, Record leftRecord, List<File> rightFiles, List<Record> rightRecords, JoinType joinType) throws Throwable { for(File rightFile : rightFiles) { BufferedReader rightReader = new BufferedReader(new FileReader(rightFile)); Record rightRecord = read(rightReader); while(rightRecord != null){ if( joinType == JoinType.LeftOuterJoin || joinType == JoinType.RightOuterJoin || joinType == JoinType.FullOuterJoin || joinType == JoinType.InnerJoin ) { write(outputFile, leftRecord, rightRecord); } rightRecord = read(rightReader); } rightReader.close(); } for(Record rightRecord : rightRecords) { if( joinType == JoinType.LeftOuterJoin || joinType == JoinType.RightOuterJoin || joinType == JoinType.FullOuterJoin || joinType == JoinType.InnerJoin ) { write(outputFile, leftRecord, rightRecord); } } } /** * consume all records having key (either to a single list or multiple files) each file will * store a buffer full of data. The right record returned represents the outside flow (key is * already positioned to next one or null) so we can't use this record in below while loop or * within this block in general when comparing current key. The trick is to keep consuming * from a List. When it becomes empty, re-fill it from the next file until all files have * been consumed (and the last node in the list is read). The next outside iteration will be * ready to be processed (either it will be null or it points to the next biggest key * @throws Throwable * */ private Record consume(String key, BufferedReader reader, List<Record> records, List<File> files, long bufferMaxRecordLines ) throws Throwable { boolean processComplete = false; Record record = records.get(records.size() - 1); while(!processComplete){ long recordCount = records.size(); if( record.getKey().compareTo(key) == 0 ){ record = read(reader); while( record != null && record.getKey().compareTo(key) == 0 && recordCount < bufferMaxRecordLines ) { records.add(record); recordCount++; record = read(reader); } } processComplete = true; // if record is null, we are done if( record != null ) { // if the key has changed, we are done if( record.getKey().compareTo(key) == 0 ) { // Same key means we have exhausted the buffer. // Dump entire buffer into a file. The list of file // pointers will keep track of the files ... processComplete = false; dumpBufferToFile(records, files); records.clear(); records.add(record); } } } return record; } /** * Dump all records in List of Record objects to a file. Then, add that * file to List of File objects * * NEED TO PLACE A LIMIT ON NUMBER OF FILE POINTERS (check size of file list) * * @param records * @param files * @throws Throwable */ private void dumpBufferToFile(List<Record> records, List<File> files) throws Throwable { String prefix = "joiner_" + files.size() + 1; String suffix = ".dat"; File file = File.createTempFile(prefix, suffix, new File("cache")); BufferedWriter writer = new BufferedWriter(new FileWriter(file)); for( Record record : records ) { writer.write( record.dump() ); } files.add(file); writer.flush(); writer.close(); }

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  • Most efficient way to implement delta time

    - by Starkers
    Here's one way to implement delta time: /// init /// var duration = 5000, currentTime = Date.now(); // and create cube, scene, camera ect ////// function animate() { /// determine delta /// var now = Date.now(), deltat = now - currentTime, currentTime = now, scalar = deltat / duration, angle = (Math.PI * 2) * scalar; ////// /// animate /// cube.rotation.y += angle; ////// /// update /// requestAnimationFrame(render); ////// } Could someone confirm I know how it works? Here what I think is going on: Firstly, we set duration at 5000, which how long the loop will take to complete in an ideal world. With a computer that is slow/busy, let's say the animation loop takes twice as long as it should, so 10000: When this happens, the scalar is set to 2.0: scalar = deltat / duration scalar = 10000 / 5000 scalar = 2.0 We now times all animation by twice as much: angle = (Math.PI * 2) * scalar; angle = (Math.PI * 2) * 2.0; angle = (Math.PI * 4) // which is 2 rotations When we do this, the cube rotation will appear to 'jump', but this is good because the animation remains real-time. With a computer that is going too quickly, let's say the animation loop takes half as long as it should, so 2500: When this happens, the scalar is set to 0.5: scalar = deltat / duration scalar = 2500 / 5000 scalar = 0.5 We now times all animation by a half: angle = (Math.PI * 2) * scalar; angle = (Math.PI * 2) * 0.5; angle = (Math.PI * 1) // which is half a rotation When we do this, the cube won't jump at all, and the animation remains real time, and doesn't speed up. However, would I be right in thinking this doesn't alter how hard the computer is working? I mean it still goes through the loop as fast as it can, and it still has render the whole scene, just with different smaller angles! So this a bad way to implement delta time, right? Now let's pretend the computer is taking exactly as long as it should, so 5000: When this happens, the scalar is set to 1.0: angle = (Math.PI * 2) * scalar; angle = (Math.PI * 2) * 1; angle = (Math.PI * 2) // which is 1 rotation When we do this, everything is timsed by 1, so nothing is changed. We'd get the same result if we weren't using delta time at all! My questions are as follows Mostly importantly, have I got the right end of the stick here? How do we know to set the duration to 5000 ? Or can it be any number? I'm a bit vague about the "computer going too quickly". Is there a way loop less often rather than reduce the animation steps? Seems like a better idea. Using this method, do all of our animations need to be timesed by the scalar? Do we have to hunt down every last one and times it? Is this the best way to implement delta time? I think not, due to the fact the computer can go nuts and all we do is divide each animation step and because we need to hunt down every step and times it by the scalar. Not a very nice DSL, as it were. So what is the best way to implement delta time? Below is one way that I do not really get but may be a better way to implement delta time. Could someone explain please? // Globals INV_MAX_FPS = 1 / 60; frameDelta = 0; clock = new THREE.Clock(); // In the animation loop (the requestAnimationFrame callback)… frameDelta += clock.getDelta(); // API: "Get the seconds passed since the last call to this method." while (frameDelta >= INV_MAX_FPS) { update(INV_MAX_FPS); // calculate physics frameDelta -= INV_MAX_FPS; } How I think this works: Firstly we set INV_MAX_FPS to 0.01666666666 How we will use this number number does not jump out at me. We then intialize a frameDelta which stores how long the last loop took to run. Come the first loop frameDelta is not greater than INV_MAX_FPS so the loop is not run (0 = 0.01666666666). So nothing happens. Now I really don't know what would cause this to happen, but let's pretend that the loop we just went through took 2 seconds to complete: We set frameDelta to 2: frameDelta += clock.getDelta(); frameDelta += 2.00 Now we run an animation thanks to update(0.01666666666). Again what is relevance of 0.01666666666?? And then we take away 0.01666666666 from the frameDelta: frameDelta -= INV_MAX_FPS; frameDelta = frameDelta - INV_MAX_FPS; frameDelta = 2 - 0.01666666666 frameDelta = 1.98333333334 So let's go into the second loop. Let's say it took 2(? Why not 2? Or 12? I am a bit confused): frameDelta += clock.getDelta(); frameDelta = frameDelta + clock.getDelta(); frameDelta = 1.98333333334 + 2 frameDelta = 3.98333333334 This time we enter the while loop because 3.98333333334 = 0.01666666666 We run update We take away 0.01666666666 from frameDelta again: frameDelta -= INV_MAX_FPS; frameDelta = frameDelta - INV_MAX_FPS; frameDelta = 3.98333333334 - 0.01666666666 frameDelta = 3.96666666668 Now let's pretend the loop is super quick and runs in just 0.1 seconds and continues to do this. (Because the computer isn't busy any more). Basically, the update function will be run, and every loop we take away 0.01666666666 from the frameDelta untill the frameDelta is less than 0.01666666666. And then nothing happens until the computer runs slowly again? Could someone shed some light please? Does the update() update the scalar or something like that and we still have to times everything by the scalar like in the first example?

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  • Optimizing a thread safe Java NIO / Serialization / FIFO Queue [migrated]

    - by trialcodr
    I've written a thread safe, persistent FIFO for Serializable items. The reason for reinventing the wheel is that we simply can't afford any third party dependencies in this project and want to keep this really simple. The problem is it isn't fast enough. Most of it is undoubtedly due to reading and writing directly to disk but I think we should be able to squeeze a bit more out of it anyway. Any ideas on how to improve the performance of the 'take'- and 'add'-methods? /** * <code>DiskQueue</code> Persistent, thread safe FIFO queue for * <code>Serializable</code> items. */ public class DiskQueue<ItemT extends Serializable> { public static final int EMPTY_OFFS = -1; public static final int LONG_SIZE = 8; public static final int HEADER_SIZE = LONG_SIZE * 2; private InputStream inputStream; private OutputStream outputStream; private RandomAccessFile file; private FileChannel channel; private long offs = EMPTY_OFFS; private long size = 0; public DiskQueue(String filename) { try { boolean fileExists = new File(filename).exists(); file = new RandomAccessFile(filename, "rwd"); if (fileExists) { size = file.readLong(); offs = file.readLong(); } else { file.writeLong(size); file.writeLong(offs); } } catch (FileNotFoundException e) { throw new RuntimeException(e); } catch (IOException e) { throw new RuntimeException(e); } channel = file.getChannel(); inputStream = Channels.newInputStream(channel); outputStream = Channels.newOutputStream(channel); } /** * Add item to end of queue. */ public void add(ItemT item) { try { synchronized (this) { channel.position(channel.size()); ObjectOutputStream s = new ObjectOutputStream(outputStream); s.writeObject(item); s.flush(); size++; file.seek(0); file.writeLong(size); if (offs == EMPTY_OFFS) { offs = HEADER_SIZE; file.writeLong(offs); } notify(); } } catch (IOException e) { throw new RuntimeException(e); } } /** * Clears overhead by moving the remaining items up and shortening the file. */ public synchronized void defrag() { if (offs > HEADER_SIZE && size > 0) { try { long totalBytes = channel.size() - offs; ByteBuffer buffer = ByteBuffer.allocateDirect((int) totalBytes); channel.position(offs); for (int bytes = 0; bytes < totalBytes;) { int res = channel.read(buffer); if (res == -1) { throw new IOException("Failed to read data into buffer"); } bytes += res; } channel.position(HEADER_SIZE); buffer.flip(); for (int bytes = 0; bytes < totalBytes;) { int res = channel.write(buffer); if (res == -1) { throw new IOException("Failed to write buffer to file"); } bytes += res; } offs = HEADER_SIZE; file.seek(LONG_SIZE); file.writeLong(offs); file.setLength(HEADER_SIZE + totalBytes); } catch (IOException e) { throw new RuntimeException(e); } } } /** * Returns the queue overhead in bytes. */ public synchronized long overhead() { return (offs == EMPTY_OFFS) ? 0 : offs - HEADER_SIZE; } /** * Returns the first item in the queue, blocks if queue is empty. */ public ItemT peek() throws InterruptedException { block(); synchronized (this) { if (offs != EMPTY_OFFS) { return readItem(); } } return peek(); } /** * Returns the number of remaining items in queue. */ public synchronized long size() { return size; } /** * Removes and returns the first item in the queue, blocks if queue is empty. */ public ItemT take() throws InterruptedException { block(); try { synchronized (this) { if (offs != EMPTY_OFFS) { ItemT result = readItem(); size--; offs = channel.position(); file.seek(0); if (offs == channel.size()) { truncate(); } file.writeLong(size); file.writeLong(offs); return result; } } return take(); } catch (IOException e) { throw new RuntimeException(e); } } /** * Throw away all items and reset the file. */ public synchronized void truncate() { try { offs = EMPTY_OFFS; file.setLength(HEADER_SIZE); size = 0; } catch (IOException e) { throw new RuntimeException(e); } } /** * Block until an item is available. */ protected void block() throws InterruptedException { while (offs == EMPTY_OFFS) { try { synchronized (this) { wait(); file.seek(LONG_SIZE); offs = file.readLong(); } } catch (IOException e) { throw new RuntimeException(e); } } } /** * Read and return item. */ @SuppressWarnings("unchecked") protected ItemT readItem() { try { channel.position(offs); return (ItemT) new ObjectInputStream(inputStream).readObject(); } catch (ClassNotFoundException e) { throw new RuntimeException(e); } catch (IOException e) { throw new RuntimeException(e); } } }

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  • how would you debug this javascript problem?

    - by pedalpete
    I've been travelling and developing for the past few weeks. The site I'm developing was running well. Then, the other day, i connected to a network and the page 'looked' fine, but it turns out the javascript wasn't running. I checked firebug, and there were no errors, as I was suspecting that maybe a script didn't load (I'm using the google api for jQuery and jQuery UI, as well as loading google maps api and fbconnect). I would suspect that if the issue was with one of these pages not loading I would get an error, and yet there was nothing. Thinking maybe i didn't connect properly or something, i reconnected to the network and even restarted my computer, as well as trying to run the local version. I got nothing. The local version not running also hinted to me that it was the loading of an external javascript which caused the problem. I let it pass as something strange with that one network. Unfortunately now I'm 100s of miles away. Today my brother sent me an e-mail that the network he was on at the airport wouldn't load my page. Same issue. Everything is laid out properly, and part of the layout is set in Javascript, so clearly javascript is running. he too got no errors. Of course, he got on his plane, and now he is no longer at the airport. Now the site works on his computer (and i haven't changed anything). How on earth would you go about figuring out what happened in this situation? That is two of maybe 12 or so networks. But I have no idea how i would find a network that doesn't work (and living in a small town, it could be difficult for me to find a network that doesn't work). Any ideas? The site is still in Dev, so I'd rather not post a link just yet (but could in a few days). What I can see not working is the javascript functions which are called on load, and on click. So i do think it is a javascript issue, but no errors. This wouldn't be as HUGE an issue if I could find and sit on one of these networks, but I can't. So what would you do? EDIT ---------------------------------------------------------- the first function(s - their linked) that doesn't get called is below. I've cut the code of at the .ajax call as the call wasn't being made. function getResultsFromForm(){ jQuery('form#filterList input.button').hide(); var searchAddress=jQuery('form#filterList input#searchTxt').val(); if(searchAddress=='' || searchAddress=='<?php echo $searchLocation; ?>'){ mapShow(20, -40, 0, 'areaMap', 2); jQuery('form#filterList input.button').show(); return; } if (GBrowserIsCompatible()) { var geo = new GClientGeocoder(); geo.setBaseCountryCode(cl.address.country); geo.getLocations(searchAddress, function (result) { if(!result.Placemark && searchAddress!='<?php echo $searchLocation; ?>'){ jQuery('span#addressNotFound').text('<?php echo $addressNotFound; ?>').slideDown('slow'); jQuery('form#filterList input.button').show(); } else { jQuery('span#addressNotFound').slideUp('slow').empty(); jQuery('span#headerLocal').text(searchAddress); var date = new Date(); date.setTime(date.getTime() + (8 * 24 * 60 * 60 * 1000)); jQuery.cookie('address', searchAddress, { expires: date}); var accuracy= result.Placemark[0].AddressDetails.Accuracy; var lat = result.Placemark[0].Point.coordinates[1]; var long = result.Placemark[0].Point.coordinates[0]; lat=parseFloat(lat); long=parseFloat(long); var getTab=jQuery('div#tabs div#active').attr('class'); jQuery('div#tabs').show(); loadForecast(lat, long, getTab, 'true', 0); var zoom=zoomLevel(); mapShow(lat, long, accuracy, 'areaMap', zoom ); } }); } } function zoomLevel(){ var zoomarray= new Array(); zoomarray=jQuery('span.viewDist').attr('id'); zoomarray=zoomarray.split("-"); var zoom=zoomarray[1]; if(zoom==''){ zoom=5; } zoom=parseFloat(zoom); return(zoom); } function loadForecast(lat, long, type, loadForecast, page){ jQuery('div#holdForecast').empty(); var date = new Date(); var d = date.getDate(); var day = (d < 10) ? '0' + d : d; var m = date.getMonth() + 1; var month = (m < 10) ? '0' + m : m; var year='2009'; toDate=year+'-'+month+'-'+day; var genre=jQuery('span.genreblock span#updateGenre').html(); var numDays=''; var numResults=''; var range=jQuery('span.viewDist').attr('id'); var dateRange = jQuery('.updateDate').attr('id'); jQuery('div#holdShows ul.showList').html('<li class="show"><div class="showData"><center><img src="../hwImages/loading.gif"/></center></div></li>'); jQuery('div#holdShows ul.'+type+'List').livequery(function(){ jQuery.ajax({ type: "GET", url: "processes/formatShows.php", data: "output=&genre="+genre+"&numResults="+numResults+"&date="+toDate+"&dateRange="+dateRange+"&range="+range+"&lat="+lat+"&long="+long+'&page='+page, success: function(response){ EDIT 2 ----------------------------------------------------------------------------- Please keep in mind that the problem is not that I can't load the site, the site works fine on most connections, but there are times when the site doesn't work, and no errors are thrown, and nothing changes. My brother couldn't run it earlier today while I had no problems, so it was something to do with his location/network. HOWEVER, the page loads, he had a connection, it was his first time visiting the site, so nothing could have been cashed. Same with when I had the issue a few days before. I didn't change anything, and I got to a different network and everything worked fine.

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  • Traditional IO vs memory-mapped

    - by Senne
    I'm trying to illustrate the difference in performance between traditional IO and memory mapped files in java to students. I found an example somewhere on internet but not everything is clear to me, I don't even think all steps are nececery. I read a lot about it here and there but I'm not convinced about a correct implementation of neither of them. The code I try to understand is: public class FileCopy{ public static void main(String args[]){ if (args.length < 1){ System.out.println(" Wrong usage!"); System.out.println(" Correct usage is : java FileCopy <large file with full path>"); System.exit(0); } String inFileName = args[0]; File inFile = new File(inFileName); if (inFile.exists() != true){ System.out.println(inFileName + " does not exist!"); System.exit(0); } try{ new FileCopy().memoryMappedCopy(inFileName, inFileName+".new" ); new FileCopy().customBufferedCopy(inFileName, inFileName+".new1"); }catch(FileNotFoundException fne){ fne.printStackTrace(); }catch(IOException ioe){ ioe.printStackTrace(); }catch (Exception e){ e.printStackTrace(); } } public void memoryMappedCopy(String fromFile, String toFile ) throws Exception{ long timeIn = new Date().getTime(); // read input file RandomAccessFile rafIn = new RandomAccessFile(fromFile, "rw"); FileChannel fcIn = rafIn.getChannel(); ByteBuffer byteBuffIn = fcIn.map(FileChannel.MapMode.READ_WRITE, 0,(int) fcIn.size()); fcIn.read(byteBuffIn); byteBuffIn.flip(); RandomAccessFile rafOut = new RandomAccessFile(toFile, "rw"); FileChannel fcOut = rafOut.getChannel(); ByteBuffer writeMap = fcOut.map(FileChannel.MapMode.READ_WRITE,0,(int) fcIn.size()); writeMap.put(byteBuffIn); long timeOut = new Date().getTime(); System.out.println("Memory mapped copy Time for a file of size :" + (int) fcIn.size() +" is "+(timeOut-timeIn)); fcOut.close(); fcIn.close(); } static final int CHUNK_SIZE = 100000; static final char[] inChars = new char[CHUNK_SIZE]; public static void customBufferedCopy(String fromFile, String toFile) throws IOException{ long timeIn = new Date().getTime(); Reader in = new FileReader(fromFile); Writer out = new FileWriter(toFile); while (true) { synchronized (inChars) { int amountRead = in.read(inChars); if (amountRead == -1) { break; } out.write(inChars, 0, amountRead); } } long timeOut = new Date().getTime(); System.out.println("Custom buffered copy Time for a file of size :" + (int) new File(fromFile).length() +" is "+(timeOut-timeIn)); in.close(); out.close(); } } When exactly is it nececary to use RandomAccessFile? Here it is used to read and write in the memoryMappedCopy, is it actually nececary just to copy a file at all? Or is it a part of memorry mapping? In customBufferedCopy, why is synchronized used here? I also found a different example that -should- test the performance between the 2: public class MappedIO { private static int numOfInts = 4000000; private static int numOfUbuffInts = 200000; private abstract static class Tester { private String name; public Tester(String name) { this.name = name; } public long runTest() { System.out.print(name + ": "); try { long startTime = System.currentTimeMillis(); test(); long endTime = System.currentTimeMillis(); return (endTime - startTime); } catch (IOException e) { throw new RuntimeException(e); } } public abstract void test() throws IOException; } private static Tester[] tests = { new Tester("Stream Write") { public void test() throws IOException { DataOutputStream dos = new DataOutputStream( new BufferedOutputStream( new FileOutputStream(new File("temp.tmp")))); for(int i = 0; i < numOfInts; i++) dos.writeInt(i); dos.close(); } }, new Tester("Mapped Write") { public void test() throws IOException { FileChannel fc = new RandomAccessFile("temp.tmp", "rw") .getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_WRITE, 0, fc.size()) .asIntBuffer(); for(int i = 0; i < numOfInts; i++) ib.put(i); fc.close(); } }, new Tester("Stream Read") { public void test() throws IOException { DataInputStream dis = new DataInputStream( new BufferedInputStream( new FileInputStream("temp.tmp"))); for(int i = 0; i < numOfInts; i++) dis.readInt(); dis.close(); } }, new Tester("Mapped Read") { public void test() throws IOException { FileChannel fc = new FileInputStream( new File("temp.tmp")).getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_ONLY, 0, fc.size()) .asIntBuffer(); while(ib.hasRemaining()) ib.get(); fc.close(); } }, new Tester("Stream Read/Write") { public void test() throws IOException { RandomAccessFile raf = new RandomAccessFile( new File("temp.tmp"), "rw"); raf.writeInt(1); for(int i = 0; i < numOfUbuffInts; i++) { raf.seek(raf.length() - 4); raf.writeInt(raf.readInt()); } raf.close(); } }, new Tester("Mapped Read/Write") { public void test() throws IOException { FileChannel fc = new RandomAccessFile( new File("temp.tmp"), "rw").getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_WRITE, 0, fc.size()) .asIntBuffer(); ib.put(0); for(int i = 1; i < numOfUbuffInts; i++) ib.put(ib.get(i - 1)); fc.close(); } } }; public static void main(String[] args) { for(int i = 0; i < tests.length; i++) System.out.println(tests[i].runTest()); } } I more or less see whats going on, my output looks like this: Stream Write: 653 Mapped Write: 51 Stream Read: 651 Mapped Read: 40 Stream Read/Write: 14481 Mapped Read/Write: 6 What is makeing the Stream Read/Write so unbelievably long? And as a read/write test, to me it looks a bit pointless to read the same integer over and over (if I understand well what's going on in the Stream Read/Write) Wouldn't it be better to read int's from the previously written file and just read and write ints on the same place? Is there a better way to illustrate it? I've been breaking my head about a lot of these things for a while and I just can't get the whole picture..

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  • Calling AuditQuerySystemPolicy() (advapi32.dll) from C# returns "The parameter is incorrect"

    - by JCCyC
    The sequence is like follows: Open a policy handle with LsaOpenPolicy() (not shown) Call LsaQueryInformationPolicy() to get the number of categories; For each category: Call AuditLookupCategoryGuidFromCategoryId() to turn the enum value into a GUID; Call AuditEnumerateSubCategories() to get a list of the GUIDs of all subcategories; Call AuditQuerySystemPolicy() to get the audit policies for the subcategories. All of these work and return expected, sensible values except the last. Calling AuditQuerySystemPolicy() gets me a "The parameter is incorrect" error. I'm thinking there must be some subtle unmarshaling problem. I'm probably misinterpreting what exactly AuditEnumerateSubCategories() returns, but I'm stumped. You'll see (commented) I tried to dereference the return pointer from AuditEnumerateSubCategories() as a pointer. Doing or not doing that gives the same result. Code: #region LSA types public enum POLICY_INFORMATION_CLASS { PolicyAuditLogInformation = 1, PolicyAuditEventsInformation, PolicyPrimaryDomainInformation, PolicyPdAccountInformation, PolicyAccountDomainInformation, PolicyLsaServerRoleInformation, PolicyReplicaSourceInformation, PolicyDefaultQuotaInformation, PolicyModificationInformation, PolicyAuditFullSetInformation, PolicyAuditFullQueryInformation, PolicyDnsDomainInformation } public enum POLICY_AUDIT_EVENT_TYPE { AuditCategorySystem, AuditCategoryLogon, AuditCategoryObjectAccess, AuditCategoryPrivilegeUse, AuditCategoryDetailedTracking, AuditCategoryPolicyChange, AuditCategoryAccountManagement, AuditCategoryDirectoryServiceAccess, AuditCategoryAccountLogon } [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)] public struct POLICY_AUDIT_EVENTS_INFO { public bool AuditingMode; public IntPtr EventAuditingOptions; public UInt32 MaximumAuditEventCount; } [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)] public struct GUID { public UInt32 Data1; public UInt16 Data2; public UInt16 Data3; public Byte Data4a; public Byte Data4b; public Byte Data4c; public Byte Data4d; public Byte Data4e; public Byte Data4f; public Byte Data4g; public Byte Data4h; public override string ToString() { return Data1.ToString("x8") + "-" + Data2.ToString("x4") + "-" + Data3.ToString("x4") + "-" + Data4a.ToString("x2") + Data4b.ToString("x2") + "-" + Data4c.ToString("x2") + Data4d.ToString("x2") + Data4e.ToString("x2") + Data4f.ToString("x2") + Data4g.ToString("x2") + Data4h.ToString("x2"); } } #endregion #region LSA Imports [DllImport("kernel32.dll")] extern static int GetLastError(); [DllImport("advapi32.dll", CharSet = CharSet.Unicode, PreserveSig = true)] public static extern UInt32 LsaNtStatusToWinError( long Status); [DllImport("advapi32.dll", CharSet = CharSet.Unicode, PreserveSig = true)] public static extern long LsaOpenPolicy( ref LSA_UNICODE_STRING SystemName, ref LSA_OBJECT_ATTRIBUTES ObjectAttributes, Int32 DesiredAccess, out IntPtr PolicyHandle ); [DllImport("advapi32.dll", CharSet = CharSet.Unicode, PreserveSig = true)] public static extern long LsaClose(IntPtr PolicyHandle); [DllImport("advapi32.dll", CharSet = CharSet.Unicode, PreserveSig = true)] public static extern long LsaFreeMemory(IntPtr Buffer); [DllImport("advapi32.dll", CharSet = CharSet.Unicode, PreserveSig = true)] public static extern void AuditFree(IntPtr Buffer); [DllImport("advapi32.dll", SetLastError = true, PreserveSig = true)] public static extern long LsaQueryInformationPolicy( IntPtr PolicyHandle, POLICY_INFORMATION_CLASS InformationClass, out IntPtr Buffer); [DllImport("advapi32.dll", SetLastError = true, PreserveSig = true)] public static extern bool AuditLookupCategoryGuidFromCategoryId( POLICY_AUDIT_EVENT_TYPE AuditCategoryId, IntPtr pAuditCategoryGuid); [DllImport("advapi32.dll", SetLastError = true, PreserveSig = true)] public static extern bool AuditEnumerateSubCategories( IntPtr pAuditCategoryGuid, bool bRetrieveAllSubCategories, out IntPtr ppAuditSubCategoriesArray, out ulong pCountReturned); [DllImport("advapi32.dll", SetLastError = true, PreserveSig = true)] public static extern bool AuditQuerySystemPolicy( IntPtr pSubCategoryGuids, ulong PolicyCount, out IntPtr ppAuditPolicy); #endregion Dictionary<string, UInt32> retList = new Dictionary<string, UInt32>(); long lretVal; uint retVal; IntPtr pAuditEventsInfo; lretVal = LsaQueryInformationPolicy(policyHandle, POLICY_INFORMATION_CLASS.PolicyAuditEventsInformation, out pAuditEventsInfo); retVal = LsaNtStatusToWinError(lretVal); if (retVal != 0) { LsaClose(policyHandle); throw new System.ComponentModel.Win32Exception((int)retVal); } POLICY_AUDIT_EVENTS_INFO myAuditEventsInfo = new POLICY_AUDIT_EVENTS_INFO(); myAuditEventsInfo = (POLICY_AUDIT_EVENTS_INFO)Marshal.PtrToStructure(pAuditEventsInfo, myAuditEventsInfo.GetType()); IntPtr subCats = IntPtr.Zero; ulong nSubCats = 0; for (int audCat = 0; audCat < myAuditEventsInfo.MaximumAuditEventCount; audCat++) { GUID audCatGuid = new GUID(); if (!AuditLookupCategoryGuidFromCategoryId((POLICY_AUDIT_EVENT_TYPE)audCat, new IntPtr(&audCatGuid))) { int causingError = GetLastError(); LsaFreeMemory(pAuditEventsInfo); LsaClose(policyHandle); throw new System.ComponentModel.Win32Exception(causingError); } if (!AuditEnumerateSubCategories(new IntPtr(&audCatGuid), true, out subCats, out nSubCats)) { int causingError = GetLastError(); LsaFreeMemory(pAuditEventsInfo); LsaClose(policyHandle); throw new System.ComponentModel.Win32Exception(causingError); } // Dereference the first pointer-to-pointer to point to the first subcategory // subCats = (IntPtr)Marshal.PtrToStructure(subCats, subCats.GetType()); if (nSubCats > 0) { IntPtr audPolicies = IntPtr.Zero; if (!AuditQuerySystemPolicy(subCats, nSubCats, out audPolicies)) { int causingError = GetLastError(); if (subCats != IntPtr.Zero) AuditFree(subCats); LsaFreeMemory(pAuditEventsInfo); LsaClose(policyHandle); throw new System.ComponentModel.Win32Exception(causingError); } AUDIT_POLICY_INFORMATION myAudPol = new AUDIT_POLICY_INFORMATION(); for (ulong audSubCat = 0; audSubCat < nSubCats; audSubCat++) { // Process audPolicies[audSubCat], turn GUIDs into names, fill retList. // http://msdn.microsoft.com/en-us/library/aa373931%28VS.85%29.aspx // http://msdn.microsoft.com/en-us/library/bb648638%28VS.85%29.aspx IntPtr itemAddr = IntPtr.Zero; IntPtr itemAddrAddr = new IntPtr(audPolicies.ToInt64() + (long)(audSubCat * (ulong)Marshal.SizeOf(itemAddr))); itemAddr = (IntPtr)Marshal.PtrToStructure(itemAddrAddr, itemAddr.GetType()); myAudPol = (AUDIT_POLICY_INFORMATION)Marshal.PtrToStructure(itemAddr, myAudPol.GetType()); retList[myAudPol.AuditSubCategoryGuid.ToString()] = myAudPol.AuditingInformation; } if (audPolicies != IntPtr.Zero) AuditFree(audPolicies); } if (subCats != IntPtr.Zero) AuditFree(subCats); subCats = IntPtr.Zero; nSubCats = 0; } lretVal = LsaFreeMemory(pAuditEventsInfo); retVal = LsaNtStatusToWinError(lretVal); if (retVal != 0) throw new System.ComponentModel.Win32Exception((int)retVal); lretVal = LsaClose(policyHandle); retVal = LsaNtStatusToWinError(lretVal); if (retVal != 0) throw new System.ComponentModel.Win32Exception((int)retVal);

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  • Lazy loading of child throwing session error

    - by Thomas Buckley
    I'm the following error when calling purchaseService.updatePurchase(purchase) inside my TagController: SEVERE: Servlet.service() for servlet [PurchaseAPIServer] in context with path [/PurchaseAPIServer] threw exception [Request processing failed; nested exception is org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.app.model.Purchase.tags, no session or session was closed] with root cause org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.app.model.Purchase.tags, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:383) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:375) at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:368) at org.hibernate.collection.PersistentSet.add(PersistentSet.java:212) at com.app.model.Purchase.addTags(Purchase.java:207) at com.app.controller.TagController.createAll(TagController.java:79) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:212) at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:900) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:827) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789) at javax.servlet.http.HttpServlet.service(HttpServlet.java:641) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:309) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662) TagController: @RequestMapping(value = "purchases/{purchaseId}/tags", method = RequestMethod.POST, params = "manyTags") @ResponseStatus(HttpStatus.CREATED) public void createAll(@PathVariable("purchaseId") final Long purchaseId, @RequestBody final Tag[] entities) { Purchase purchase = purchaseService.getById(purchaseId); Set<Tag> tags = new HashSet<Tag>(Arrays.asList(entities)); purchase.addTags(tags); purchaseService.updatePurchase(purchase); } Purchase: @Entity @XmlRootElement public class Purchase implements Serializable { /** * */ private static final long serialVersionUID = 6603477834338392140L; @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @OneToMany(mappedBy = "purchase", fetch = FetchType.LAZY, cascade={CascadeType.ALL}) private Set<Tag> tags; @JsonIgnore public Set<Tag> getTags() { if (tags == null) { tags = new LinkedHashSet<Tag>(); } return tags; } public void setTags(Set<Tag> tags) { this.tags = tags; } ... } Tag: @Entity @XmlRootElement public class Tag implements Serializable { /** * */ private static final long serialVersionUID = 5165922776051697002L; @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @ManyToOne(fetch = FetchType.LAZY) @JoinColumns({@JoinColumn(name = "PURCHASEID", referencedColumnName = "ID")}) private Purchase purchase; @JsonIgnore public Purchase getPurchase() { return purchase; } public void setPurchase(Purchase purchase) { this.purchase = purchase; } } PurchaseService: @Service public class PurchaseService implements IPurchaseService { @Autowired private IPurchaseDAO purchaseDAO; public PurchaseService() { } @Transactional public List<Purchase> getAll() { return purchaseDAO.findAll(); } @Transactional public Purchase getById(Long id) { return purchaseDAO.findOne(id); } @Transactional public void addPurchase(Purchase purchase) { purchaseDAO.save(purchase); } @Transactional public void updatePurchase(Purchase purchase) { purchaseDAO.update(purchase); } } TagService: @Service public class TagService implements ITagService { @Autowired private ITagDAO tagDAO; public TagService() { } @Transactional public List<Tag> getAll() { return tagDAO.findAll(); } @Transactional public Tag getById(Long id) { return tagDAO.findOne(id); } @Transactional public void addTag(Tag tag) { tagDAO.save(tag); } @Transactional public void updateTag(Tag tag) { tagDAO.update(tag); } } Any ideas on how I can fix this? (I want to avoid using EAGER loading). Do I need to setup some form of session management for transactions? Thanks

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  • Agile Development

    - by James Oloo Onyango
    Alot of literature has and is being written about agile developement and its surrounding philosophies. In my quest to find the best way to express the importance of agile methodologies, i have found Robert C. Martin's "A Satire Of Two Companies" to be both the most concise and thorough! Enjoy the read! Rufus Inc Project Kick Off Your name is Bob. The date is January 3, 2001, and your head still aches from the recent millennial revelry. You are sitting in a conference room with several managers and a group of your peers. You are a project team leader. Your boss is there, and he has brought along all of his team leaders. His boss called the meeting. "We have a new project to develop," says your boss's boss. Call him BB. The points in his hair are so long that they scrape the ceiling. Your boss's points are just starting to grow, but he eagerly awaits the day when he can leave Brylcream stains on the acoustic tiles. BB describes the essence of the new market they have identified and the product they want to develop to exploit this market. "We must have this new project up and working by fourth quarter October 1," BB demands. "Nothing is of higher priority, so we are cancelling your current project." The reaction in the room is stunned silence. Months of work are simply going to be thrown away. Slowly, a murmur of objection begins to circulate around the conference table.   His points give off an evil green glow as BB meets the eyes of everyone in the room. One by one, that insidious stare reduces each attendee to quivering lumps of protoplasm. It is clear that he will brook no discussion on this matter. Once silence has been restored, BB says, "We need to begin immediately. How long will it take you to do the analysis?" You raise your hand. Your boss tries to stop you, but his spitwad misses you and you are unaware of his efforts.   "Sir, we can't tell you how long the analysis will take until we have some requirements." "The requirements document won't be ready for 3 or 4 weeks," BB says, his points vibrating with frustration. "So, pretend that you have the requirements in front of you now. How long will you require for analysis?" No one breathes. Everyone looks around to see whether anyone has some idea. "If analysis goes beyond April 1, we have a problem. Can you finish the analysis by then?" Your boss visibly gathers his courage: "We'll find a way, sir!" His points grow 3 mm, and your headache increases by two Tylenol. "Good." BB smiles. "Now, how long will it take to do the design?" "Sir," you say. Your boss visibly pales. He is clearly worried that his 3 mms are at risk. "Without an analysis, it will not be possible to tell you how long design will take." BB's expression shifts beyond austere.   "PRETEND you have the analysis already!" he says, while fixing you with his vacant, beady little eyes. "How long will it take you to do the design?" Two Tylenol are not going to cut it. Your boss, in a desperate attempt to save his new growth, babbles: "Well, sir, with only six months left to complete the project, design had better take no longer than 3 months."   "I'm glad you agree, Smithers!" BB says, beaming. Your boss relaxes. He knows his points are secure. After a while, he starts lightly humming the Brylcream jingle. BB continues, "So, analysis will be complete by April 1, design will be complete by July 1, and that gives you 3 months to implement the project. This meeting is an example of how well our new consensus and empowerment policies are working. Now, get out there and start working. I'll expect to see TQM plans and QIT assignments on my desk by next week. Oh, and don't forget that your crossfunctional team meetings and reports will be needed for next month's quality audit." "Forget the Tylenol," you think to yourself as you return to your cubicle. "I need bourbon."   Visibly excited, your boss comes over to you and says, "Gosh, what a great meeting. I think we're really going to do some world shaking with this project." You nod in agreement, too disgusted to do anything else. "Oh," your boss continues, "I almost forgot." He hands you a 30-page document. "Remember that the SEI is coming to do an evaluation next week. This is the evaluation guide. You need to read through it, memorize it, and then shred it. It tells you how to answer any questions that the SEI auditors ask you. It also tells you what parts of the building you are allowed to take them to and what parts to avoid. We are determined to be a CMM level 3 organization by June!"   You and your peers start working on the analysis of the new project. This is difficult because you have no requirements. But from the 10-minute introduction given by BB on that fateful morning, you have some idea of what the product is supposed to do.   Corporate process demands that you begin by creating a use case document. You and your team begin enumerating use cases and drawing oval and stick diagrams. Philosophical debates break out among the team members. There is disagreement as to whether certain use cases should be connected with <<extends>> or <<includes>> relationships. Competing models are created, but nobody knows how to evaluate them. The debate continues, effectively paralyzing progress.   After a week, somebody finds the iceberg.com Web site, which recommends disposing entirely of <<extends>> and <<includes>> and replacing them with <<precedes>> and <<uses>>. The documents on this Web site, authored by Don Sengroiux, describes a method known as stalwart-analysis, which claims to be a step-by-step method for translating use cases into design diagrams. More competing use case models are created using this new scheme, but again, people can't agree on how to evaluate them. The thrashing continues. More and more, the use case meetings are driven by emotion rather than by reason. If it weren't for the fact that you don't have requirements, you'd be pretty upset by the lack of progress you are making. The requirements document arrives on February 15. And then again on February 20, 25, and every week thereafter. Each new version contradicts the previous one. Clearly, the marketing folks who are writing the requirements, empowered though they might be, are not finding consensus.   At the same time, several new competing use case templates have been proposed by the various team members. Each template presents its own particularly creative way of delaying progress. The debates rage on. On March 1, Prudence Putrigence, the process proctor, succeeds in integrating all the competing use case forms and templates into a single, all-encompassing form. Just the blank form is 15 pages long. She has managed to include every field that appeared on all the competing templates. She also presents a 159- page document describing how to fill out the use case form. All current use cases must be rewritten according to the new standard.   You marvel to yourself that it now requires 15 pages of fill-in-the-blank and essay questions to answer the question: What should the system do when the user presses Return? The corporate process (authored by L. E. Ott, famed author of "Holistic Analysis: A Progressive Dialectic for Software Engineers") insists that you discover all primary use cases, 87 percent of all secondary use cases, and 36.274 percent of all tertiary use cases before you can complete analysis and enter the design phase. You have no idea what a tertiary use case is. So in an attempt to meet this requirement, you try to get your use case document reviewed by the marketing department, which you hope will know what a tertiary use case is.   Unfortunately, the marketing folks are too busy with sales support to talk to you. Indeed, since the project started, you have not been able to get a single meeting with marketing, which has provided a never-ending stream of changing and contradictory requirements documents.   While one team has been spinning endlessly on the use case document, another team has been working out the domain model. Endless variations of UML documents are pouring out of this team. Every week, the model is reworked.   The team members can't decide whether to use <<interfaces>> or <<types>> in the model. A huge disagreement has been raging on the proper syntax and application of OCL. Others on the team just got back from a 5-day class on catabolism, and have been producing incredibly detailed and arcane diagrams that nobody else can fathom.   On March 27, with one week to go before analysis is to be complete, you have produced a sea of documents and diagrams but are no closer to a cogent analysis of the problem than you were on January 3. **** And then, a miracle happens.   **** On Saturday, April 1, you check your e-mail from home. You see a memo from your boss to BB. It states unequivocally that you are done with the analysis! You phone your boss and complain. "How could you have told BB that we were done with the analysis?" "Have you looked at a calendar lately?" he responds. "It's April 1!" The irony of that date does not escape you. "But we have so much more to think about. So much more to analyze! We haven't even decided whether to use <<extends>> or <<precedes>>!" "Where is your evidence that you are not done?" inquires your boss, impatiently. "Whaaa . . . ." But he cuts you off. "Analysis can go on forever; it has to be stopped at some point. And since this is the date it was scheduled to stop, it has been stopped. Now, on Monday, I want you to gather up all existing analysis materials and put them into a public folder. Release that folder to Prudence so that she can log it in the CM system by Monday afternoon. Then get busy and start designing."   As you hang up the phone, you begin to consider the benefits of keeping a bottle of bourbon in your bottom desk drawer. They threw a party to celebrate the on-time completion of the analysis phase. BB gave a colon-stirring speech on empowerment. And your boss, another 3 mm taller, congratulated his team on the incredible show of unity and teamwork. Finally, the CIO takes the stage to tell everyone that the SEI audit went very well and to thank everyone for studying and shredding the evaluation guides that were passed out. Level 3 now seems assured and will be awarded by June. (Scuttlebutt has it that managers at the level of BB and above are to receive significant bonuses once the SEI awards level 3.)   As the weeks flow by, you and your team work on the design of the system. Of course, you find that the analysis that the design is supposedly based on is flawedno, useless; no, worse than useless. But when you tell your boss that you need to go back and work some more on the analysis to shore up its weaker sections, he simply states, "The analysis phase is over. The only allowable activity is design. Now get back to it."   So, you and your team hack the design as best you can, unsure of whether the requirements have been properly analyzed. Of course, it really doesn't matter much, since the requirements document is still thrashing with weekly revisions, and the marketing department still refuses to meet with you.     The design is a nightmare. Your boss recently misread a book named The Finish Line in which the author, Mark DeThomaso, blithely suggested that design documents should be taken down to code-level detail. "If we are going to be working at that level of detail," you ask, "why don't we simply write the code instead?" "Because then you wouldn't be designing, of course. And the only allowable activity in the design phase is design!" "Besides," he continues, "we have just purchased a companywide license for Dandelion! This tool enables 'Round the Horn Engineering!' You are to transfer all design diagrams into this tool. It will automatically generate our code for us! It will also keep the design diagrams in sync with the code!" Your boss hands you a brightly colored shrinkwrapped box containing the Dandelion distribution. You accept it numbly and shuffle off to your cubicle. Twelve hours, eight crashes, one disk reformatting, and eight shots of 151 later, you finally have the tool installed on your server. You consider the week your team will lose while attending Dandelion training. Then you smile and think, "Any week I'm not here is a good week." Design diagram after design diagram is created by your team. Dandelion makes it very difficult to draw these diagrams. There are dozens and dozens of deeply nested dialog boxes with funny text fields and check boxes that must all be filled in correctly. And then there's the problem of moving classes between packages. At first, these diagram are driven from the use cases. But the requirements are changing so often that the use cases rapidly become meaningless. Debates rage about whether VISITOR or DECORATOR design patterns should be used. One developer refuses to use VISITOR in any form, claiming that it's not a properly object-oriented construct. Someone refuses to use multiple inheritance, since it is the spawn of the devil. Review meetings rapidly degenerate into debates about the meaning of object orientation, the definition of analysis versus design, or when to use aggregation versus association. Midway through the design cycle, the marketing folks announce that they have rethought the focus of the system. Their new requirements document is completely restructured. They have eliminated several major feature areas and replaced them with feature areas that they anticipate customer surveys will show to be more appropriate. You tell your boss that these changes mean that you need to reanalyze and redesign much of the system. But he says, "The analysis phase is system. But he says, "The analysis phase is over. The only allowable activity is design. Now get back to it."   You suggest that it might be better to create a simple prototype to show to the marketing folks and even some potential customers. But your boss says, "The analysis phase is over. The only allowable activity is design. Now get back to it." Hack, hack, hack, hack. You try to create some kind of a design document that might reflect the new requirements documents. However, the revolution of the requirements has not caused them to stop thrashing. Indeed, if anything, the wild oscillations of the requirements document have only increased in frequency and amplitude.   You slog your way through them.   On June 15, the Dandelion database gets corrupted. Apparently, the corruption has been progressive. Small errors in the DB accumulated over the months into bigger and bigger errors. Eventually, the CASE tool just stopped working. Of course, the slowly encroaching corruption is present on all the backups. Calls to the Dandelion technical support line go unanswered for several days. Finally, you receive a brief e-mail from Dandelion, informing you that this is a known problem and that the solution is to purchase the new version, which they promise will be ready some time next quarter, and then reenter all the diagrams by hand.   ****   Then, on July 1 another miracle happens! You are done with the design!   Rather than go to your boss and complain, you stock your middle desk drawer with some vodka.   **** They threw a party to celebrate the on-time completion of the design phase and their graduation to CMM level 3. This time, you find BB's speech so stirring that you have to use the restroom before it begins. New banners and plaques are all over your workplace. They show pictures of eagles and mountain climbers, and they talk about teamwork and empowerment. They read better after a few scotches. That reminds you that you need to clear out your file cabinet to make room for the brandy. You and your team begin to code. But you rapidly discover that the design is lacking in some significant areas. Actually, it's lacking any significance at all. You convene a design session in one of the conference rooms to try to work through some of the nastier problems. But your boss catches you at it and disbands the meeting, saying, "The design phase is over. The only allowable activity is coding. Now get back to it."   ****   The code generated by Dandelion is really hideous. It turns out that you and your team were using association and aggregation the wrong way, after all. All the generated code has to be edited to correct these flaws. Editing this code is extremely difficult because it has been instrumented with ugly comment blocks that have special syntax that Dandelion needs in order to keep the diagrams in sync with the code. If you accidentally alter one of these comments, the diagrams will be regenerated incorrectly. It turns out that "Round the Horn Engineering" requires an awful lot of effort. The more you try to keep the code compatible with Dandelion, the more errors Dandelion generates. In the end, you give up and decide to keep the diagrams up to date manually. A second later, you decide that there's no point in keeping the diagrams up to date at all. Besides, who has time?   Your boss hires a consultant to build tools to count the number of lines of code that are being produced. He puts a big thermometer graph on the wall with the number 1,000,000 on the top. Every day, he extends the red line to show how many lines have been added. Three days after the thermometer appears on the wall, your boss stops you in the hall. "That graph isn't growing quickly enough. We need to have a million lines done by October 1." "We aren't even sh-sh-sure that the proshect will require a m-million linezh," you blather. "We have to have a million lines done by October 1," your boss reiterates. His points have grown again, and the Grecian formula he uses on them creates an aura of authority and competence. "Are you sure your comment blocks are big enough?" Then, in a flash of managerial insight, he says, "I have it! I want you to institute a new policy among the engineers. No line of code is to be longer than 20 characters. Any such line must be split into two or more preferably more. All existing code needs to be reworked to this standard. That'll get our line count up!"   You decide not to tell him that this will require two unscheduled work months. You decide not to tell him anything at all. You decide that intravenous injections of pure ethanol are the only solution. You make the appropriate arrangements. Hack, hack, hack, and hack. You and your team madly code away. By August 1, your boss, frowning at the thermometer on the wall, institutes a mandatory 50-hour workweek.   Hack, hack, hack, and hack. By September 1st, the thermometer is at 1.2 million lines and your boss asks you to write a report describing why you exceeded the coding budget by 20 percent. He institutes mandatory Saturdays and demands that the project be brought back down to a million lines. You start a campaign of remerging lines. Hack, hack, hack, and hack. Tempers are flaring; people are quitting; QA is raining trouble reports down on you. Customers are demanding installation and user manuals; salespeople are demanding advance demonstrations for special customers; the requirements document is still thrashing, the marketing folks are complaining that the product isn't anything like they specified, and the liquor store won't accept your credit card anymore. Something has to give.    On September 15, BB calls a meeting. As he enters the room, his points are emitting clouds of steam. When he speaks, the bass overtones of his carefully manicured voice cause the pit of your stomach to roll over. "The QA manager has told me that this project has less than 50 percent of the required features implemented. He has also informed me that the system crashes all the time, yields wrong results, and is hideously slow. He has also complained that he cannot keep up with the continuous train of daily releases, each more buggy than the last!" He stops for a few seconds, visibly trying to compose himself. "The QA manager estimates that, at this rate of development, we won't be able to ship the product until December!" Actually, you think it's more like March, but you don't say anything. "December!" BB roars with such derision that people duck their heads as though he were pointing an assault rifle at them. "December is absolutely out of the question. Team leaders, I want new estimates on my desk in the morning. I am hereby mandating 65-hour work weeks until this project is complete. And it better be complete by November 1."   As he leaves the conference room, he is heard to mutter: "Empowermentbah!" * * * Your boss is bald; his points are mounted on BB's wall. The fluorescent lights reflecting off his pate momentarily dazzle you. "Do you have anything to drink?" he asks. Having just finished your last bottle of Boone's Farm, you pull a bottle of Thunderbird from your bookshelf and pour it into his coffee mug. "What's it going to take to get this project done? " he asks. "We need to freeze the requirements, analyze them, design them, and then implement them," you say callously. "By November 1?" your boss exclaims incredulously. "No way! Just get back to coding the damned thing." He storms out, scratching his vacant head.   A few days later, you find that your boss has been transferred to the corporate research division. Turnover has skyrocketed. Customers, informed at the last minute that their orders cannot be fulfilled on time, have begun to cancel their orders. Marketing is re-evaluating whether this product aligns with the overall goals of the company. Memos fly, heads roll, policies change, and things are, overall, pretty grim. Finally, by March, after far too many sixty-five hour weeks, a very shaky version of the software is ready. In the field, bug-discovery rates are high, and the technical support staff are at their wits' end, trying to cope with the complaints and demands of the irate customers. Nobody is happy.   In April, BB decides to buy his way out of the problem by licensing a product produced by Rupert Industries and redistributing it. The customers are mollified, the marketing folks are smug, and you are laid off.     Rupert Industries: Project Alpha   Your name is Robert. The date is January 3, 2001. The quiet hours spent with your family this holiday have left you refreshed and ready for work. You are sitting in a conference room with your team of professionals. The manager of the division called the meeting. "We have some ideas for a new project," says the division manager. Call him Russ. He is a high-strung British chap with more energy than a fusion reactor. He is ambitious and driven but understands the value of a team. Russ describes the essence of the new market opportunity the company has identified and introduces you to Jane, the marketing manager, who is responsible for defining the products that will address it. Addressing you, Jane says, "We'd like to start defining our first product offering as soon as possible. When can you and your team meet with me?" You reply, "We'll be done with the current iteration of our project this Friday. We can spare a few hours for you between now and then. After that, we'll take a few people from the team and dedicate them to you. We'll begin hiring their replacements and the new people for your team immediately." "Great," says Russ, "but I want you to understand that it is critical that we have something to exhibit at the trade show coming up this July. If we can't be there with something significant, we'll lose the opportunity."   "I understand," you reply. "I don't yet know what it is that you have in mind, but I'm sure we can have something by July. I just can't tell you what that something will be right now. In any case, you and Jane are going to have complete control over what we developers do, so you can rest assured that by July, you'll have the most important things that can be accomplished in that time ready to exhibit."   Russ nods in satisfaction. He knows how this works. Your team has always kept him advised and allowed him to steer their development. He has the utmost confidence that your team will work on the most important things first and will produce a high-quality product.   * * *   "So, Robert," says Jane at their first meeting, "How does your team feel about being split up?" "We'll miss working with each other," you answer, "but some of us were getting pretty tired of that last project and are looking forward to a change. So, what are you people cooking up?" Jane beams. "You know how much trouble our customers currently have . . ." And she spends a half hour or so describing the problem and possible solution. "OK, wait a second" you respond. "I need to be clear about this." And so you and Jane talk about how this system might work. Some of her ideas aren't fully formed. You suggest possible solutions. She likes some of them. You continue discussing.   During the discussion, as each new topic is addressed, Jane writes user story cards. Each card represents something that the new system has to do. The cards accumulate on the table and are spread out in front of you. Both you and Jane point at them, pick them up, and make notes on them as you discuss the stories. The cards are powerful mnemonic devices that you can use to represent complex ideas that are barely formed.   At the end of the meeting, you say, "OK, I've got a general idea of what you want. I'm going to talk to the team about it. I imagine they'll want to run some experiments with various database structures and presentation formats. Next time we meet, it'll be as a group, and we'll start identifying the most important features of the system."   A week later, your nascent team meets with Jane. They spread the existing user story cards out on the table and begin to get into some of the details of the system. The meeting is very dynamic. Jane presents the stories in the order of their importance. There is much discussion about each one. The developers are concerned about keeping the stories small enough to estimate and test. So they continually ask Jane to split one story into several smaller stories. Jane is concerned that each story have a clear business value and priority, so as she splits them, she makes sure that this stays true.   The stories accumulate on the table. Jane writes them, but the developers make notes on them as needed. Nobody tries to capture everything that is said; the cards are not meant to capture everything but are simply reminders of the conversation.   As the developers become more comfortable with the stories, they begin writing estimates on them. These estimates are crude and budgetary, but they give Jane an idea of what the story will cost.   At the end of the meeting, it is clear that many more stories could be discussed. It is also clear that the most important stories have been addressed and that they represent several months worth of work. Jane closes the meeting by taking the cards with her and promising to have a proposal for the first release in the morning.   * * *   The next morning, you reconvene the meeting. Jane chooses five cards and places them on the table. "According to your estimates, these cards represent about one perfect team-week's worth of work. The last iteration of the previous project managed to get one perfect team-week done in 3 real weeks. If we can get these five stories done in 3 weeks, we'll be able to demonstrate them to Russ. That will make him feel very comfortable about our progress." Jane is pushing it. The sheepish look on her face lets you know that she knows it too. You reply, "Jane, this is a new team, working on a new project. It's a bit presumptuous to expect that our velocity will be the same as the previous team's. However, I met with the team yesterday afternoon, and we all agreed that our initial velocity should, in fact, be set to one perfectweek for every 3 real-weeks. So you've lucked out on this one." "Just remember," you continue, "that the story estimates and the story velocity are very tentative at this point. We'll learn more when we plan the iteration and even more when we implement it."   Jane looks over her glasses at you as if to say "Who's the boss around here, anyway?" and then smiles and says, "Yeah, don't worry. I know the drill by now."Jane then puts 15 more cards on the table. She says, "If we can get all these cards done by the end of March, we can turn the system over to our beta test customers. And we'll get good feedback from them."   You reply, "OK, so we've got our first iteration defined, and we have the stories for the next three iterations after that. These four iterations will make our first release."   "So," says Jane, can you really do these five stories in the next 3 weeks?" "I don't know for sure, Jane," you reply. "Let's break them down into tasks and see what we get."   So Jane, you, and your team spend the next several hours taking each of the five stories that Jane chose for the first iteration and breaking them down into small tasks. The developers quickly realize that some of the tasks can be shared between stories and that other tasks have commonalities that can probably be taken advantage of. It is clear that potential designs are popping into the developers' heads. From time to time, they form little discussion knots and scribble UML diagrams on some cards.   Soon, the whiteboard is filled with the tasks that, once completed, will implement the five stories for this iteration. You start the sign-up process by saying, "OK, let's sign up for these tasks." "I'll take the initial database generation." Says Pete. "That's what I did on the last project, and this doesn't look very different. I estimate it at two of my perfect workdays." "OK, well, then, I'll take the login screen," says Joe. "Aw, darn," says Elaine, the junior member of the team, "I've never done a GUI, and kinda wanted to try that one."   "Ah, the impatience of youth," Joe says sagely, with a wink in your direction. "You can assist me with it, young Jedi." To Jane: "I think it'll take me about three of my perfect workdays."   One by one, the developers sign up for tasks and estimate them in terms of their own perfect workdays. Both you and Jane know that it is best to let the developers volunteer for tasks than to assign the tasks to them. You also know full well that you daren't challenge any of the developers' estimates. You know these people, and you trust them. You know that they are going to do the very best they can.   The developers know that they can't sign up for more perfect workdays than they finished in the last iteration they worked on. Once each developer has filled his or her schedule for the iteration, they stop signing up for tasks.   Eventually, all the developers have stopped signing up for tasks. But, of course, tasks are still left on the board.   "I was worried that that might happen," you say, "OK, there's only one thing to do, Jane. We've got too much to do in this iteration. What stories or tasks can we remove?" Jane sighs. She knows that this is the only option. Working overtime at the beginning of a project is insane, and projects where she's tried it have not fared well.   So Jane starts to remove the least-important functionality. "Well, we really don't need the login screen just yet. We can simply start the system in the logged-in state." "Rats!" cries Elaine. "I really wanted to do that." "Patience, grasshopper." says Joe. "Those who wait for the bees to leave the hive will not have lips too swollen to relish the honey." Elaine looks confused. Everyone looks confused. "So . . .," Jane continues, "I think we can also do away with . . ." And so, bit by bit, the list of tasks shrinks. Developers who lose a task sign up for one of the remaining ones.   The negotiation is not painless. Several times, Jane exhibits obvious frustration and impatience. Once, when tensions are especially high, Elaine volunteers, "I'll work extra hard to make up some of the missing time." You are about to correct her when, fortunately, Joe looks her in the eye and says, "When once you proceed down the dark path, forever will it dominate your destiny."   In the end, an iteration acceptable to Jane is reached. It's not what Jane wanted. Indeed, it is significantly less. But it's something the team feels that can be achieved in the next 3 weeks.   And, after all, it still addresses the most important things that Jane wanted in the iteration. "So, Jane," you say when things had quieted down a bit, "when can we expect acceptance tests from you?" Jane sighs. This is the other side of the coin. For every story the development team implements,   Jane must supply a suite of acceptance tests that prove that it works. And the team needs these long before the end of the iteration, since they will certainly point out differences in the way Jane and the developers imagine the system's behaviour.   "I'll get you some example test scripts today," Jane promises. "I'll add to them every day after that. You'll have the entire suite by the middle of the iteration."   * * *   The iteration begins on Monday morning with a flurry of Class, Responsibilities, Collaborators sessions. By midmorning, all the developers have assembled into pairs and are rapidly coding away. "And now, my young apprentice," Joe says to Elaine, "you shall learn the mysteries of test-first design!"   "Wow, that sounds pretty rad," Elaine replies. "How do you do it?" Joe beams. It's clear that he has been anticipating this moment. "OK, what does the code do right now?" "Huh?" replied Elaine, "It doesn't do anything at all; there is no code."   "So, consider our task; can you think of something the code should do?" "Sure," Elaine said with youthful assurance, "First, it should connect to the database." "And thereupon, what must needs be required to connecteth the database?" "You sure talk weird," laughed Elaine. "I think we'd have to get the database object from some registry and call the Connect() method. "Ah, astute young wizard. Thou perceives correctly that we requireth an object within which we can cacheth the database object." "Is 'cacheth' really a word?" "It is when I say it! So, what test can we write that we know the database registry should pass?" Elaine sighs. She knows she'll just have to play along. "We should be able to create a database object and pass it to the registry in a Store() method. And then we should be able to pull it out of the registry with a Get() method and make sure it's the same object." "Oh, well said, my prepubescent sprite!" "Hay!" "So, now, let's write a test function that proves your case." "But shouldn't we write the database object and registry object first?" "Ah, you've much to learn, my young impatient one. Just write the test first." "But it won't even compile!" "Are you sure? What if it did?" "Uh . . ." "Just write the test, Elaine. Trust me." And so Joe, Elaine, and all the other developers began to code their tasks, one test case at a time. The room in which they worked was abuzz with the conversations between the pairs. The murmur was punctuated by an occasional high five when a pair managed to finish a task or a difficult test case.   As development proceeded, the developers changed partners once or twice a day. Each developer got to see what all the others were doing, and so knowledge of the code spread generally throughout the team.   Whenever a pair finished something significant whether a whole task or simply an important part of a task they integrated what they had with the rest of the system. Thus, the code base grew daily, and integration difficulties were minimized.   The developers communicated with Jane on a daily basis. They'd go to her whenever they had a question about the functionality of the system or the interpretation of an acceptance test case.   Jane, good as her word, supplied the team with a steady stream of acceptance test scripts. The team read these carefully and thereby gained a much better understanding of what Jane expected the system to do. By the beginning of the second week, there was enough functionality to demonstrate to Jane. She watched eagerly as the demonstration passed test case after test case. "This is really cool," Jane said as the demonstration finally ended. "But this doesn't seem like one-third of the tasks. Is your velocity slower than anticipated?"   You grimace. You'd been waiting for a good time to mention this to Jane but now she was forcing the issue. "Yes, unfortunately, we are going more slowly than we had expected. The new application server we are using is turning out to be a pain to configure. Also, it takes forever to reboot, and we have to reboot it whenever we make even the slightest change to its configuration."   Jane eyes you with suspicion. The stress of last Monday's negotiations had still not entirely dissipated. She says, "And what does this mean to our schedule? We can't slip it again, we just can't. Russ will have a fit! He'll haul us all into the woodshed and ream us some new ones."   You look Jane right in the eyes. There's no pleasant way to give someone news like this. So you just blurt out, "Look, if things keep going like they're going, we're not going to be done with everything by next Friday. Now it's possible that we'll figure out a way to go faster. But, frankly, I wouldn't depend on that. You should start thinking about one or two tasks that could be removed from the iteration without ruining the demonstration for Russ. Come hell or high water, we are going to give that demonstration on Friday, and I don't think you want us to choose which tasks to omit."   "Aw forchrisakes!" Jane barely manages to stifle yelling that last word as she stalks away, shaking her head. Not for the first time, you say to yourself, "Nobody ever promised me project management would be easy." You are pretty sure it won't be the last time, either.   Actually, things went a bit better than you had hoped. The team did, in fact, have to drop one task from the iteration, but Jane had chosen wisely, and the demonstration for Russ went without a hitch. Russ was not impressed with the progress, but neither was he dismayed. He simply said, "This is pretty good. But remember, we have to be able to demonstrate this system at the trade show in July, and at this rate, it doesn't look like you'll have all that much to show." Jane, whose attitude had improved dramatically with the completion of the iteration, responded to Russ by saying, "Russ, this team is working hard, and well. When July comes around, I am confident that we'll have something significant to demonstrate. It won't be everything, and some of it may be smoke and mirrors, but we'll have something."   Painful though the last iteration was, it had calibrated your velocity numbers. The next iteration went much better. Not because your team got more done than in the last iteration but simply because the team didn't have to remove any tasks or stories in the middle of the iteration.   By the start of the fourth iteration, a natural rhythm has been established. Jane, you, and the team know exactly what to expect from one another. The team is running hard, but the pace is sustainable. You are confident that the team can keep up this pace for a year or more.   The number of surprises in the schedule diminishes to near zero; however, the number of surprises in the requirements does not. Jane and Russ frequently look over the growing system and make recommendations or changes to the existing functionality. But all parties realize that these changes take time and must be scheduled. So the changes do not cause anyone's expectations to be violated. In March, there is a major demonstration of the system to the board of directors. The system is very limited and is not yet in a form good enough to take to the trade show, but progress is steady, and the board is reasonably impressed.   The second release goes even more smoothly than the first. By now, the team has figured out a way to automate Jane's acceptance test scripts. The team has also refactored the design of the system to the point that it is really easy to add new features and change old ones. The second release was done by the end of June and was taken to the trade show. It had less in it than Jane and Russ would have liked, but it did demonstrate the most important features of the system. Although customers at the trade show noticed that certain features were missing, they were very impressed overall. You, Russ, and Jane all returned from the trade show with smiles on your faces. You all felt as though this project was a winner.   Indeed, many months later, you are contacted by Rufus Inc. That company had been working on a system like this for its internal operations. Rufus has canceled the development of that system after a death-march project and is negotiating to license your technology for its environment.   Indeed, things are looking up!

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  • The HTG Guide to Using a Bluetooth Keyboard with Your Android Device

    - by Matt Klein
    Android devices aren’t usually associated with physical keyboards. But, since Google is now bundling their QuickOffice app with the newly-released Kit-Kat, it appears inevitable that at least some Android tablets (particularly 10-inch models) will take on more productivity roles. In recent years, physical keyboards have been rendered obsolete by swipe style input methods such as Swype and Google Keyboard. Physical keyboards tend to make phones thick and plump, and that won’t fly today when thin (and even flexible and curved) is in vogue. So, you’ll be hard-pressed to find smartphone manufacturers launching new models with physical keyboards, thus rendering sliders to a past chapter in mobile phone evolution. It makes sense to ditch the clunky keyboard phone in favor of a lighter, thinner model. You’re going to carry around in your pocket or purse all day, why have that extra bulk and weight? That said, there is sound logic behind pairing tablets with keyboards. Microsoft continues to plod forward with its Surface models, and while critics continue to lavish praise on the iPad, its functionality is obviously enhanced and extended when you add a physical keyboard. Apple even has an entire page devoted specifically to iPad-compatible keyboards. But an Android tablet and a keyboard? Does such a thing even exist? They do actually. There are docking keyboards and keyboard/case combinations, there’s the Asus Transformer family, Logitech markets a Windows 8 keyboard that speaks “Android”, and these are just to name a few. So we know that keyboard products that are designed to work with Android exist, but what about an everyday Bluetooth keyboard you might use with Windows or OS X? How-To Geek wanted look at how viable it is to use such a keyboard with Android. We conducted some research and examined some lists of Android keyboard shortcuts. Most of what we found was long outdated. Many of the shortcuts don’t even apply anymore, while others just didn’t work. Regardless, after a little experimentation and a dash of customization, it turns out using a keyboard with Android is kind of fun, and who knows, maybe it will catch on. Setting things up Setting up a Bluetooth keyboard with Android is very easy. First, you’ll need a Bluetooth keyboard and of course an Android device, preferably running version 4.1 (Jelly Bean) or higher. For our test, we paired a second-generation Google Nexus 7 running Android 4.3 with a Samsung Series 7 keyboard. In Android, enable Bluetooth if it isn’t already on. We’d like to note that if you don’t normally use Bluetooth accessories and peripherals with your Android device (or any device really), it’s best practice to leave Bluetooth off because, like GPS, it drains the device’s battery more quickly. To enable Bluetooth, simply go to “Settings” -> “Bluetooth” and tap the slider button to “On”. To set up the keyboard, make sure it is on and then tap “Bluetooth” in the Android settings. On the resulting screen, your Android device should automatically search for and hopefully find your keyboard. If you don’t get it right the first time, simply turn the keyboard on again and then tap “Search for Devices” to try again. If it still doesn’t work, make sure you have fresh batteries and the keyboard isn’t paired to another device. If it is, you will need to unpair it before it will work with your Android device (consult your keyboard manufacturer’s documentation or Google if you don’t know how to do this). When Android finds your keyboard, select it under “Available Devices” … … and you should be prompted to type in a code: If successful, you will see that device is now “Connected” and you’re ready to go. If you want to test things out, try pressing the “Windows” key (“Apple” or “Command”) + ESC, and you will be whisked to your Home screen. So, what can you do? Traditional Mac and Windows users know there’s usually a keyboard shortcut for just about everything (and if there isn’t, there’s all kinds of ways to remap keys to do a variety of commands, tasks, and functions). So where does Android fall in terms of baked-in keyboard commands? There answer to that is kind of enough, but not too much. There are definitely established combos you can use to get around, but they aren’t clear and there doesn’t appear to be any one authority on what they are. Still, there is enough keyboard functionality in Android to make it a viable option, if only for those times when you need to get something done (long e-mail or important document) and an on-screen keyboard simply won’t do. It’s important to remember that Android is, and likely always will be a touch-first interface. That said, it does make some concessions to physical keyboards. In other words, you can get around Android fairly well without having to lift your hands off the keys, but you will still have to tap the screen regularly, unless you add a mouse. For example, you can wake your device by tapping a key rather than pressing its power button. However, if your device is slide or pattern-locked, then you’ll have to use the touchscreen to unlock it – a password or PIN however, works seamlessly with a keyboard – other things like widgets and app controls and features, have to be tapped. You get the idea. Keyboard shortcuts and navigation As we said, baked-in keyboard shortcut combos aren’t necessarily abundant nor apparent. The one thing you can always do is search. Any time you want to Google something, start typing from the Home screen and the search screen will automatically open and begin displaying results. Other than that, here is what we were able to figure out: ESC = go back CTRL + ESC = menu CTRL + ALT + DEL = restart (no questions asked) ALT + SPACE = search page (say “OK Google” to voice search) ALT + TAB (ALT + SHIFT + TAB) = switch tasks Also, if you have designated volume function keys, those will probably work too. There’s also some dedicated app shortcuts like calculator, Gmail, and a few others: CMD + A = calculator CMD + C = contacts CMD + E = e-mail CMD + G = Gmail CMD + L = Calendar CMD + P = Play Music CMD + Y = YouTube Overall, it’s not a long comprehensive list and there’s no dedicated keyboard combos for the full array of Google’s products. Granted, it’s hard to imagine getting a lot of mileage out of a keyboard with Maps but with something like Keep, you could type out long, detailed lists on your tablet, and then view them on your smartphone when you go out shopping. You can also use the arrow keys to navigate your Home screen over shortcuts and open the app drawer. When something on the screen is selected, it will be highlighted in blue. Press “Enter” to open your selection. Additionally, if an app has its own set of shortcuts, e.g. Gmail has quite a few unique shortcuts to it, as does Chrome, some – though not many – will work in Android (not for YouTube though). Also, many “universal” shortcuts such as Copy (CTRL + C), Cut (CTRL + X), Paste (CTRL + V), and Select All (CTRL + A) work where needed – such as in instant messaging, e-mail, social media apps, etc. Creating custom application shortcuts What about custom shortcuts? When we were researching this article, we were under the impression that it was possible to assign keyboard combinations to specific apps, such as you could do on older Android versions such as Gingerbread. This no long seems to be the case and nowhere in “Settings” could we find a way to assign hotkey combos to any of our favorite, oft-used apps or functions. If you do want custom keyboard shortcuts, what can you do? Luckily, there’s an app on Google Play that allows you to, among other things, create custom app shortcuts. It is called External Keyboard Helper (EKH) and while there is a free demo version, the pay version is only a few bucks. We decided to give EKH a whirl and through a little experimentation and finally reading the developer’s how-to, we found we could map custom keyboard combos to just about anything. To do this, first open the application and you’ll see the main app screen. Don’t worry about choosing a custom layout or anything like that, you want to go straight to the “Advanced settings”: In the “Advanced settings” select “Application shortcuts” to continue: You can have up to 16 custom application shortcuts. We are going to create a custom shortcut to the Facebook app. We choose “A0”, and from the resulting list, Facebook. You can do this for any number of apps, services, and settings. As you can now see, the Facebook app has now been linked to application-zero (A0): Go back to the “Advanced settings” and choose “Customize keyboard mappings”: You will be prompted to create a custom keyboard layout so we choose “Custom 1”: When you choose to create a custom layout, you can do a great many more things with your keyboard. For example, many keyboards have predefined function (Fn) keys, which you can map to your tablet’s brightness controls, toggle WiFi on/off, and much more. A word of advice, the application automatically remaps certain keys when you create a custom layout. This might mess up some existing keyboard combos. If you simply want to add some functionality to your keyboard, you can go ahead and delete EKH’s default changes and start your custom layout from scratch. To create a new combo, select “Add new key mapping”: For our new shortcut, we are going to assign the Facebook app to open when we key in “ALT + F”. To do this, we press the “F” key while in the “Scancode” field and we see it returns a value of “33”. If we wanted to use a different key, we can press “Change” and scan another key’s numerical value. We now want to assign the “ALT” key to application “A0”, previously designated as the Facebook app. In the “AltGr” field, we enter “A0” and then “Save” our custom combo. And now we see our new application shortcut. Now, as long as we’re using our custom layout, every time we press “ALT + F”, the Facebook app will launch: External Keyboard Helper extends far beyond simple application shortcuts and if you are looking for deeper keyboard customization options, you should definitely check it out. Among other things, EKH also supports dozens of languages, allows you to quickly switch between layouts using a key or combo, add up to 16 custom text shortcuts, and much more! It can be had on Google Play for $2.53 for the full version, but you can try the demo version for free. More extensive documentation on how to use the app is also available. Android? Keyboard? Sure, why not? Unlike traditional desktop operating systems, you don’t need a physical keyboard and mouse to use a mobile operating system. You can buy an iPad or Nexus 10 or Galaxy Note, and never need another accessory or peripheral – they work as intended right out of the box. It’s even possible you can write the next great American novel on one these devices, though that might require a lot of practice and patience. That said, using a keyboard with Android is kind of fun. It’s not revelatory but it does elevate the experience. You don’t even need to add customizations (though they are nice) because there are enough existing keyboard shortcuts in Android to make it usable. Plus, when it comes to inputting text such as in an editor or terminal application, we fully advocate big, physical keyboards. Bottom line, if you’re looking for a way to enhance your Android tablet, give a keyboard a chance. Do you use your Android device for productivity? Is a physical keyboard an important part of your setup? Do you have any shortcuts that we missed? Sound off in the comments and let us know what you think.     

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  • Using Completed User Stories to Estimate Future User Stories

    - by David Kaczynski
    In Scrum/Agile, the complexity of a user story can be estimated in story points. After completing some user stories, a programmer or team of programmers can use those experiences to better estimate how much time it might take to complete a future user story. Is there a methodology for breaking down the complexity of user stories into quantifiable or quantifiable attributes? For example, User Story X requires a rich, new view in the GUI, but User Story X can perform most of its functionality using existing business logic on the server. On a scale of 1 to 10, User Story X has a complexity of 7 on the client and a complexity of 2 on the server. After User Story X is completed, someone asks how long would it take to complete User Story Y, which has a complexity of 3 on the client and 6 on the server. Looking at how long it took to complete User Story X, we can make an educated estimate on how long it might take to complete User Story Y. I can imagine some other details: The complexity of one attribute (such as complexity of client) could have sub-attributes, such as number of steps in a sequence, function points, etc. Several other attributes that could be considered as well, such as the programmer's familiarity with the system or the number of components/interfaces involved These attributes could be accumulated into some sort of user story checklist. To reiterate: is there an existing methodology for decomposing the complexity of a user story into complexity of attributes/sub-attributes, or is using completed user stories as indicators in estimating future user stories more of an informal process?

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  • XAMPP vs WAMP security and other on Windows XP

    - by typoknig
    Not long ago I found WAMP and thought it was a God send because it had all the things I wanted/needed (Apache, PHP, MySQL, and phpMyAdmin) all built into one installer. One thing about WAMP has been making me mad is an error I get in phpMyAdmin about the advanced features not working. I have tried to fix that error long enough on that error for long enough. http://stackoverflow.com/questions/2688385/problem-with-phpmyadmin-advanced-features I now read that most people prefer XAMPP over WAMP, but I am a bit concerned that XAMPP might have some extra security holes with Mercury and Perl, two thing that I don't really need or want right now. Are my security concerns justified or not? Is there any other reasons to go with XAMPP over WAMP or vice versa?

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  • The Social Business Thought Leaders - John Hagel

    - by kellsey.ruppel
    While many European economies are on the brink of a recession between increasing taxation and mounting loss of jobs and bankruptcy filing rates, there's an understandable risk of losing sight of the deeper forces at play. Yet instead of surrendering to uncertainty and trying to survive in the short term, many organizations are feeling the urge to be better prepared to thrive in these complex times by developing a more articulated long term understanding of both the opportunities / challenges ahead. For example: What long-term economic, technological and societal changes are rolling out? Which foundational dynamics will affect our companies' performance, productivity, competition, and innovative potential in the upcoming decades? How will digital infrastructure change our business landscape? What kind of capabilities will be key to compete in a market shaped by growing turbulence, unpredictability and volatility? Breaking out from a strictly cyclical thinking, studies such as the Shift Index by John Hagel, Co-Chairman of the Center for the Edge at Deloitte & Touche (See Measuring the forces of long-term change - The 2009 Shift Index), depict a worrying performance challenge that affected every industry in the entire US economy over the last 45 years. Amidst a more than doubled competitive intensity of the market, and even with an improved labor productivity, the actual performance of US firms has consistently fallen to 25% of what it was in 1965. Most of this reported value is shifting from institutions and organizations to individuals, whether they are customers or young creative talent. To thrive in the digital economy and reverse declining performance trends, companies will have to fundamentally rethink their management approach by moving from knowledge stocks to knowledge flows, from scalable efficiency to scalable learning, from push organizations to pull organizations. Based on the outcomes of the Shift Index and on the book The Power of Pull, the first episode of the Social Business Thought-Leaders features John Hagel to provide strategic insights on how companies will succeed in the 21st century.

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  • Login loop in Snow Leopard

    - by hgpc
    I can't get out of a login loop of a particular admin user. After entering the password the login screen is shown again after about a minute. Other users work fine. It started happening after a simple reboot. Can you please help me? Thank you! Tried to no avail: Change the password Remove the password Repair disk (no errors) Boot in safe mode Reinstall Snow Leopard and updating to 10.6.6 Remove content of ~/Library/Caches Removed content of ~/Library/Preferences Replaced /etc/authorization with Install DVD copy The system.log mentions a crash report. I'm including both below. system.log Jan 8 02:43:30 loginwindow218: Login Window - Returned from Security Agent Jan 8 02:43:30 loginwindow218: USER_PROCESS: 218 console Jan 8 02:44:42 kernel[0]: Jan 8 02:44:43: --- last message repeated 1 time --- Jan 8 02:44:43 com.apple.launchd[1] (com.apple.loginwindow218): Job appears to have crashed: Bus error Jan 8 02:44:43 com.apple.UserEventAgent-LoginWindow223: ALF error: cannot find useragent 1102 Jan 8 02:44:43 com.apple.UserEventAgent-LoginWindow223: plugin.UserEventAgentFactory: called with typeID=FC86416D-6164-2070-726F-70735C216EC0 Jan 8 02:44:43 /System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow233: Login Window Application Started Jan 8 02:44:43 SecurityAgent228: CGSShutdownServerConnections: Detaching application from window server Jan 8 02:44:43 com.apple.ReportCrash.Root232: 2011-01-08 02:44:43.936 ReportCrash232:2903 Saved crash report for loginwindow218 version ??? (???) to /Library/Logs/DiagnosticReports/loginwindow_2011-01-08-024443_localhost.crash Jan 8 02:44:44 SecurityAgent228: MIG: server died: CGSReleaseShmem : Cannot release shared memory Jan 8 02:44:44 SecurityAgent228: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Jan 8 02:44:44 SecurityAgent228: CGSDisplayServerShutdown: Detaching display subsystem from window server Jan 8 02:44:44 SecurityAgent228: HIToolbox: received notification of WindowServer event port death. Jan 8 02:44:44 SecurityAgent228: port matched the WindowServer port created in BindCGSToRunLoop Jan 8 02:44:44 loginwindow233: Login Window Started Security Agent Jan 8 02:44:44 WindowServer234: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Jan 8 02:44:44 com.apple.WindowServer234: Sat Jan 8 02:44:44 .local WindowServer234 <Error>: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Jan 8 02:44:54 SecurityAgent243: NSSecureTextFieldCell detected a field editor ((null)) that is not a NSTextView subclass designed to work with the cell. Ignoring... Crash report Process: loginwindow 218 Path: /System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow Identifier: loginwindow Version: ??? (???) Code Type: X86-64 (Native) Parent Process: launchd [1] Date/Time: 2011-01-08 02:44:42.748 +0100 OS Version: Mac OS X 10.6.6 (10J567) Report Version: 6 Exception Type: EXC_BAD_ACCESS (SIGBUS) Exception Codes: 0x000000000000000a, 0x000000010075b000 Crashed Thread: 0 Dispatch queue: com.apple.main-thread Thread 0 Crashed: Dispatch queue: com.apple.main-thread 0 com.apple.security 0x00007fff801c6e8b Security::ReadSection::at(unsigned int) const + 25 1 com.apple.security 0x00007fff801c632f Security::DbVersion::open() + 123 2 com.apple.security 0x00007fff801c5e41 Security::DbVersion::DbVersion(Security::AppleDatabase const&, Security::RefPointer<Security::AtomicBufferedFile> const&) + 179 3 com.apple.security 0x00007fff801c594e Security::DbModifier::getDbVersion(bool) + 330 4 com.apple.security 0x00007fff801c57f5 Security::DbModifier::openDatabase() + 33 5 com.apple.security 0x00007fff801c5439 Security::Database::_dbOpen(Security::DatabaseSession&, unsigned int, Security::AccessCredentials const*, void const*) + 221 6 com.apple.security 0x00007fff801c4841 Security::DatabaseManager::dbOpen(Security::DatabaseSession&, Security::DbName const&, unsigned int, Security::AccessCredentials const*, void const*) + 77 7 com.apple.security 0x00007fff801c4723 Security::DatabaseSession::DbOpen(char const*, cssm_net_address const*, unsigned int, Security::AccessCredentials const*, void const*, long&) + 285 8 com.apple.security 0x00007fff801d8414 cssm_DbOpen(long, char const*, cssm_net_address const*, unsigned int, cssm_access_credentials const*, void const*, long*) + 108 9 com.apple.security 0x00007fff801d7fba CSSM_DL_DbOpen + 106 10 com.apple.security 0x00007fff801d62f6 Security::CssmClient::DbImpl::open() + 162 11 com.apple.security 0x00007fff801d8977 SSDatabaseImpl::open(Security::DLDbIdentifier const&) + 53 12 com.apple.security 0x00007fff801d8715 SSDLSession::DbOpen(char const*, cssm_net_address const*, unsigned int, Security::AccessCredentials const*, void const*, long&) + 263 13 com.apple.security 0x00007fff801d8414 cssm_DbOpen(long, char const*, cssm_net_address const*, unsigned int, cssm_access_credentials const*, void const*, long*) + 108 14 com.apple.security 0x00007fff801d7fba CSSM_DL_DbOpen + 106 15 com.apple.security 0x00007fff801d62f6 Security::CssmClient::DbImpl::open() + 162 16 com.apple.security 0x00007fff802fa786 Security::CssmClient::DbImpl::unlock(cssm_data const&) + 28 17 com.apple.security 0x00007fff80275b5d Security::KeychainCore::KeychainImpl::unlock(Security::CssmData const&) + 89 18 com.apple.security 0x00007fff80291a06 Security::KeychainCore::StorageManager::login(unsigned int, void const*, unsigned int, void const*) + 3336 19 com.apple.security 0x00007fff802854d3 SecKeychainLogin + 91 20 com.apple.loginwindow 0x000000010000dfc5 0x100000000 + 57285 21 com.apple.loginwindow 0x000000010000cfb4 0x100000000 + 53172 22 com.apple.Foundation 0x00007fff8721e44f __NSThreadPerformPerform + 219 23 com.apple.CoreFoundation 0x00007fff82627401 __CFRunLoopDoSources0 + 1361 24 com.apple.CoreFoundation 0x00007fff826255f9 __CFRunLoopRun + 873 25 com.apple.CoreFoundation 0x00007fff82624dbf CFRunLoopRunSpecific + 575 26 com.apple.HIToolbox 0x00007fff8444493a RunCurrentEventLoopInMode + 333 27 com.apple.HIToolbox 0x00007fff8444473f ReceiveNextEventCommon + 310 28 com.apple.HIToolbox 0x00007fff844445f8 BlockUntilNextEventMatchingListInMode + 59 29 com.apple.AppKit 0x00007fff80b01e64 _DPSNextEvent + 718 30 com.apple.AppKit 0x00007fff80b017a9 -NSApplication nextEventMatchingMask:untilDate:inMode:dequeue: + 155 31 com.apple.AppKit 0x00007fff80ac748b -NSApplication run + 395 32 com.apple.loginwindow 0x0000000100004b16 0x100000000 + 19222 33 com.apple.loginwindow 0x0000000100004580 0x100000000 + 17792 Thread 1: Dispatch queue: com.apple.libdispatch-manager 0 libSystem.B.dylib 0x00007fff8755216a kevent + 10 1 libSystem.B.dylib 0x00007fff8755403d _dispatch_mgr_invoke + 154 2 libSystem.B.dylib 0x00007fff87553d14 _dispatch_queue_invoke + 185 3 libSystem.B.dylib 0x00007fff8755383e _dispatch_worker_thread2 + 252 4 libSystem.B.dylib 0x00007fff87553168 _pthread_wqthread + 353 5 libSystem.B.dylib 0x00007fff87553005 start_wqthread + 13 Thread 0 crashed with X86 Thread State (64-bit): rax: 0x000000010075b000 rbx: 0x00007fff5fbfd990 rcx: 0x00007fff875439da rdx: 0x0000000000000000 rdi: 0x00007fff5fbfd990 rsi: 0x0000000000000000 rbp: 0x00007fff5fbfd5d0 rsp: 0x00007fff5fbfd5d0 r8: 0x0000000000000007 r9: 0x0000000000000000 r10: 0x00007fff8753beda r11: 0x0000000000000202 r12: 0x0000000100133e78 r13: 0x00007fff5fbfda50 r14: 0x00007fff5fbfda50 r15: 0x00007fff5fbfdaa0 rip: 0x00007fff801c6e8b rfl: 0x0000000000010287 cr2: 0x000000010075b000

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  • Postgres 9.0 locking up, 100% CPU

    - by Jake
    We are having a problem where our Postgres 9.0 server occasionally locks up and kills our webapp. Restarting Postgres fixes the problem. Here's what I've been able to observe: First, usage of one CPU jumps to 100% for a few minutes Disk operations drop to ~0 during this time Database operations drop to 0 (blocks and tuples per sec) Logs show during this time: WARNING: worker took too long to start; cancelled WARNING: worker took too long to start; cancelled No Queries in logs (only those over 200ms are logged) No unusually long-running queries logged before or during Then the second CPU jumps to 100% The number of postgres processes jumps from the usual 8-10 to ~20 Matched by a spike in Postgres Blocks per second (about twice normal) Logs show LOG: could not accept SSL connection: EOF detected Queries are running but slow Restarting postgres returns everything to normal Setup: Server: Amazon EC2 Large Ubuntu 10.04.2 LTS Postgres 9.0.3 Dedicated DB server Does anyone have any idea what's causing this? Or any suggestions about what else I should be checking out?

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  • How to cross-reference many character encodings with ASCII OR UTFx?

    - by Garet Claborn
    I'm working with a binary structure, the goal of which is to index the significance of specific bits for any character encoding so that we may trigger events while doing specific checks against the profile. Each character encoding scheme has an associated system record. This record's leading value will be a C++ unsigned long long binary value and signifies the length, in bits, of encoded characters. Following the length are three values, each is a bit field of that length. offset_mask - defines the occurrence of non-printable characters within the min,max of print_mask range_mask - defines the occurrence of the most popular 50% of printable characters print_mask - defines the occurrence value of printable characters The structure of profiles has changed from the op of this question. Most likely I will try to factorize or compress these values in the long-term instead of starting out with ranges after reading more. I have to write some of the core functionality for these main reasons. It has to fit into a particular event architecture we are using, Better understanding of character encoding. I'm about to need it. Integrating into non-linear design is excluding many libraries without special hooks. I'm unsure if there is a standard, cross-encoding mechanism for communicating such data already. I'm just starting to look into how chardet might do profiling as suggested by @amon. The Unicode BOM would be easily enough (for my current project) if all encodings were Unicode. Of course ideally, one would like to support all encodings, but I'm not asking about implementation - only the general case. How can these profiles be efficiently populated, to produce a set of bitmasks which we can use to match strings with common characters in multiple languages? If you have any editing suggestions please feel free, I am a lightweight when it comes to localization, which is why I'm trying to reach out to the more experienced. Any caveats you may be able to help with will be appreciated.

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  • How to backup in Fedora-13?

    - by Ramy
    I just bought a 1.5T HDD and a disk enclosure. I connected this disk to my laptop via the provided USB cable. I then used the following command: rsync -r -t -v --progress --delete -c -l -z / /media/C4E41A11E41A0678/Moonface_BKP/ I ran this for a long (long long) time when i noticed that what had been backed up to the HDD began to be backed up. In other words, when i ran the command, it created a /media directory and a C4... directory below that and kept recursively backing up this directory (since, I suppose, I was backing up the hard drive itself, too). So...what's the proper way to use rsync?

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  • How to Handle frame rates and synchronizing screen repaints

    - by David Kroukamp
    I would first off say sorry if the title is worded incorrectly. Okay now let me give the scenario I'm creating a 2 player fighting game, An average battle will include a Map (moving/still) and 2 characters (which are rendered by redrawing a varying amount of sprites one after the other). Now at the moment I have a single game loop limiting me to a set number of frames per second (using Java): Timer timer = new Timer(0, new AbstractAction() { @Override public void actionPerformed(ActionEvent e) { long beginTime; //The time when the cycle begun long timeDiff; //The time it took for the cycle to execute int sleepTime; //ms to sleep (< 0 if we're behind) int fps = 1000 / 40; beginTime = System.nanoTime() / 1000000; //execute loop to update check collisions and draw gameLoop(); //Calculate how long did the cycle take timeDiff = System.nanoTime() / 1000000 - beginTime; //Calculate sleep time sleepTime = fps - (int) (timeDiff); if (sleepTime > 0) {//If sleepTime > 0 we're OK ((Timer)e.getSource()).setDelay(sleepTime); } } }); timer.start(); in gameLoop() characters are drawn to the screen ( a character holds an array of images which consists of their current sprites) every gameLoop() call will change the characters current sprite to the next and loop if the end is reached. But as you can imagine if a sprite is only 3 images in length than calling gameLoop() 40 times will cause the characters movement to be drawn 40/3=13 times. This causes a few minor anomilies in the sprited for some charcters So my question is how would I go about delivering a set amount of frames per second in when I have 2 characters on screen with varying amount of sprites?

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  • Why do I get Apps in Windows 8 listed as 'Not available' sometimes?

    - by keith
    What affects this, and if possible, how can I prevent this? Or maybe how can I get them to be available sooner or all the time? This pretty much happens to my game apps connected to Xbox live and a few others from time to time. It never happened before I updated the computer, but I haven't had the PC long anyway. Could it be that after updates that need a restart it does this as well (I've done two of those so far)? Anyhow, I'm frustrated, I keep clicking on a app and it not responding. The problem fixes itself at some point, but I have not been able to stare at my PC long enough to figure out how long it takes or what happened.

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  • Semantic Form Markup for Yes or No Questions - Or Should I Tell my Designers to Bugger Off?

    - by sholsinger
    I frequently receive mock-ups of HTML forms with the following prototype: Some long winded yes or no question?   (o) Yes   ( ) No The (o) and ( ) in this prototype represent radio buttons. My personal view is that if the question has only a true or false value then it should be a check box. That said, I have seen this sort of "layout" from almost every designer I've ever worked with. If I were not to question their decision, or question the client's decision, I'd probably mark it up like this: <p class="pseudo_label">Some long winded yes or no question?</p> <input type="radio" name="the_question" id="the_question_yes" value="1"> <label for="the_question_yes" class="after_radio">Yes</label> <input type="radio" name="the_question" id="the_question_no" value="0"> <label for="the_question_no" class="after_radio">No</label> I really don't want to do that. I want to push back and convince them that this should really be a check box and not two radio buttons. But my question is, if I can't convince them – you're welcome to help me try – how should I code that original design requirement such that it is semantic and at least understandable for screen reader users? If I were able to convince my tormentors to change their minds, I would likely code it in the following fashion: <label for="the_question">Some long winded yes or no question?</label> <input type="checkbox" name="the_question" id="the_question" value="1"> What do you think about this issue? Should I push back? Possibly more importantly is either way semantically correct?

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  • C#: Handling Notifications: inheritance, events, or delegates?

    - by James Michael Hare
    Often times as developers we have to design a class where we get notification when certain things happen. In older object-oriented code this would often be implemented by overriding methods -- with events, delegates, and interfaces, however, we have far more elegant options. So, when should you use each of these methods and what are their strengths and weaknesses? Now, for the purposes of this article when I say notification, I'm just talking about ways for a class to let a user know that something has occurred. This can be through any programmatic means such as inheritance, events, delegates, etc. So let's build some context. I'm sitting here thinking about a provider neutral messaging layer for the place I work, and I got to the point where I needed to design the message subscriber which will receive messages from the message bus. Basically, what we want is to be able to create a message listener and have it be called whenever a new message arrives. Now, back before the flood we would have done this via inheritance and an abstract class: 1:  2: // using inheritance - omitting argument null checks and halt logic 3: public abstract class MessageListener 4: { 5: private ISubscriber _subscriber; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber) 11: { 12: _subscriber = subscriber; 13: _messageThread = new Thread(MessageLoop); 14: _messageThread.Start(); 15: } 16:  17: // user will override this to process their messages 18: protected abstract void OnMessageReceived(Message msg); 19:  20: // handle the looping in the thread 21: private void MessageLoop() 22: { 23: while(!_isHalted) 24: { 25: // as long as processing, wait 1 second for message 26: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 27: if(msg != null) 28: { 29: OnMessageReceived(msg); 30: } 31: } 32: } 33: ... 34: } It seems so odd to write this kind of code now. Does it feel odd to you? Maybe it's just because I've gotten so used to delegation that I really don't like the feel of this. To me it is akin to saying that if I want to drive my car I need to derive a new instance of it just to put myself in the driver's seat. And yet, unquestionably, five years ago I would have probably written the code as you see above. To me, inheritance is a flawed approach for notifications due to several reasons: Inheritance is one of the HIGHEST forms of coupling. You can't seal the listener class because it depends on sub-classing to work. Because C# does not allow multiple-inheritance, I've spent my one inheritance implementing this class. Every time you need to listen to a bus, you have to derive a class which leads to lots of trivial sub-classes. The act of consuming a message should be a separate responsibility than the act of listening for a message (SRP). Inheritance is such a strong statement (this IS-A that) that it should only be used in building type hierarchies and not for overriding use-specific behaviors and notifications. Chances are, if a class needs to be inherited to be used, it most likely is not designed as well as it could be in today's modern programming languages. So lets look at the other tools available to us for getting notified instead. Here's a few other choices to consider. Have the listener expose a MessageReceived event. Have the listener accept a new IMessageHandler interface instance. Have the listener accept an Action<Message> delegate. Really, all of these are different forms of delegation. Now, .NET events are a bit heavier than the other types of delegates in terms of run-time execution, but they are a great way to allow others using your class to subscribe to your events: 1: // using event - ommiting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private bool _isHalted = false; 6: private Thread _messageThread; 7:  8: // assign the subscriber and start the messaging loop 9: public MessageListener(ISubscriber subscriber) 10: { 11: _subscriber = subscriber; 12: _messageThread = new Thread(MessageLoop); 13: _messageThread.Start(); 14: } 15:  16: // user will override this to process their messages 17: public event Action<Message> MessageReceived; 18:  19: // handle the looping in the thread 20: private void MessageLoop() 21: { 22: while(!_isHalted) 23: { 24: // as long as processing, wait 1 second for message 25: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 26: if(msg != null && MessageReceived != null) 27: { 28: MessageReceived(msg); 29: } 30: } 31: } 32: } Note, now we can seal the class to avoid changes and the user just needs to provide a message handling method: 1: theListener.MessageReceived += CustomReceiveMethod; However, personally I don't think events hold up as well in this case because events are largely optional. To me, what is the point of a listener if you create one with no event listeners? So in my mind, use events when handling the notification is optional. So how about the delegation via interface? I personally like this method quite a bit. Basically what it does is similar to inheritance method mentioned first, but better because it makes it easy to split the part of the class that doesn't change (the base listener behavior) from the part that does change (the user-specified action after receiving a message). So assuming we had an interface like: 1: public interface IMessageHandler 2: { 3: void OnMessageReceived(Message receivedMessage); 4: } Our listener would look like this: 1: // using delegation via interface - omitting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private IMessageHandler _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, IMessageHandler handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // handle the looping in the thread 19: private void MessageLoop() 20: { 21: while(!_isHalted) 22: { 23: // as long as processing, wait 1 second for message 24: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 25: if(msg != null) 26: { 27: _handler.OnMessageReceived(msg); 28: } 29: } 30: } 31: } And they would call it by creating a class that implements IMessageHandler and pass that instance into the constructor of the listener. I like that this alleviates the issues of inheritance and essentially forces you to provide a handler (as opposed to events) on construction. Well, this is good, but personally I think we could go one step further. While I like this better than events or inheritance, it still forces you to implement a specific method name. What if that name collides? Furthermore if you have lots of these you end up either with large classes inheriting multiple interfaces to implement one method, or lots of small classes. Also, if you had one class that wanted to manage messages from two different subscribers differently, it wouldn't be able to because the interface can't be overloaded. This brings me to using delegates directly. In general, every time I think about creating an interface for something, and if that interface contains only one method, I start thinking a delegate is a better approach. Now, that said delegates don't accomplish everything an interface can. Obviously having the interface allows you to refer to the classes that implement the interface which can be very handy. In this case, though, really all you want is a method to handle the messages. So let's look at a method delegate: 1: // using delegation via delegate - omitting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private Action<Message> _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, Action<Message> handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // handle the looping in the thread 19: private void MessageLoop() 20: { 21: while(!_isHalted) 22: { 23: // as long as processing, wait 1 second for message 24: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 25: if(msg != null) 26: { 27: _handler(msg); 28: } 29: } 30: } 31: } Here the MessageListener now takes an Action<Message>.  For those of you unfamiliar with the pre-defined delegate types in .NET, that is a method with the signature: void SomeMethodName(Message). The great thing about delegates is it gives you a lot of power. You could create an anonymous delegate, a lambda, or specify any other method as long as it satisfies the Action<Message> signature. This way, you don't need to define an arbitrary helper class or name the method a specific thing. Incidentally, we could combine both the interface and delegate approach to allow maximum flexibility. Doing this, the user could either pass in a delegate, or specify a delegate interface: 1: // using delegation - give users choice of interface or delegate 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private Action<Message> _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, Action<Message> handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // passes the interface method as a delegate using method group 19: public MessageListener(ISubscriber subscriber, IMessageHandler handler) 20: : this(subscriber, handler.OnMessageReceived) 21: { 22: } 23:  24: // handle the looping in the thread 25: private void MessageLoop() 26: { 27: while(!_isHalted) 28: { 29: // as long as processing, wait 1 second for message 30: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 31: if(msg != null) 32: { 33: _handler(msg); 34: } 35: } 36: } 37: } } This is the method I tend to prefer because it allows the user of the class to choose which method works best for them. You may be curious about the actual performance of these different methods. 1: Enter iterations: 2: 1000000 3:  4: Inheritance took 4 ms. 5: Events took 7 ms. 6: Interface delegation took 4 ms. 7: Lambda delegate took 5 ms. Before you get too caught up in the numbers, however, keep in mind that this is performance over over 1,000,000 iterations. Since they are all < 10 ms which boils down to fractions of a micro-second per iteration so really any of them are a fine choice performance wise. As such, I think the choice of what to do really boils down to what you're trying to do. Here's my guidelines: Inheritance should be used only when defining a collection of related types with implementation specific behaviors, it should not be used as a hook for users to add their own functionality. Events should be used when subscription is optional or multi-cast is desired. Interface delegation should be used when you wish to refer to implementing classes by the interface type or if the type requires several methods to be implemented. Delegate method delegation should be used when you only need to provide one method and do not need to refer to implementers by the interface name.

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  • Which would be a better way to load data via ajax

    - by Mike
    I am using google maps and returning html/lat/long from my MySQL database Currently A user picks a business category e.g; "Video Production". an ajax call is sent to a CodeIgniter controller the Controller then queries the db, and returns the following data via JSON Lat/Long of the marker HTML for the popup window this is approximately 34 rows in the database across two tables per business the ajax call receives this data and then plots the marker along with the html onto the map The data that is returned from the controller is one big json object... This is done for all businesses that exist in the Video Production category (currently approx 40 businesses). As you can see, pulling this data for multiple categories (100s of businesses) can get very very taxing on the server. My question is Would it be more beneficial to modify the process flow as such: a user picks a business category e.g; "Video Production". an ajax call is sent to a CodeIgniter controller the controller then queries the database for the location base information lat/long level (used to change marker icon color) This would be a single row per business with several columns the ajax call receives this data and then plots the marker on the map when the user clicks a marker an ajax call is sent to a CodeIgniter Controller the controller queries the database for the HTML and additional data based on business_id and if not, what are some better suggestions to this problem? In summary this means rather than including the HTML and additional data along for each business, only submitting minimal location information and then re-query for that information when each business marker is clicked. Potential Downsides longer load times when a user clicks a marker icon more code?? more queries to the database

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  • La première bêta de Wordpress 3.0 est disponible, elle est plus fonctionnelle bien qu'encore partiel

    Mise à jour du 09.04.2010 par Katleen La première bêta de Wordpress 3.0 est disponible, elle est plus fonctionnelle bien qu'encore partielle L'infrastructure de blogs Wordpress vient de faire un pas en avant. Son équipe de développeurs vient en effet de publier la version bêta de Wordpress 3.0. Beaucoup de nouveaux thèmes y sont présents, même si les fonctionnalités auxquelles ils sont rattachés ne sont pas encore toutes opérationelles. Première bêta oblige, certains éléments sont encore absents ou incomplets. Au menu des nouveautés, on notera la fusion de Wordpress et de Wordpress MU qui permettra aux posseseurs de plusieurs blogs ou sites de les gérer plus facilement depuis un...

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  • Solaris cc segfaults when compiling rsync on intel platform

    - by PP
    I am trying to compile rsync-3.0.7 on Solaris 5.10 on an Intel chipset. When running ./configure I see the following (obviously erroneous lines): checking size of int... 0 checking size of long... 0 checking size of long long... 0 checking size of short... 0 checking size of int16_t... 0 checking size of uint16_t... 0 In config.log I see the following lines: configure.sh:5448: /tool/sunstudio12.1/bin/cc -xc99=all -o conftest -g -DHAVE_CONFIG_H conftest.c >&5 "conftest.c", line 123: warning: statement not reached cc: Fatal error in cc : Segmentation Fault configure.sh:5448: $? = 1 configure.sh: program exited with status 1 Segmentation fault? What could be causing a simple test script to segfault during compilation?

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  • Semantic Form Markup for Yes or No Questions

    - by sholsinger
    I frequently receive mock-ups of HTML forms with the following prototype: Some long winded yes or no question?   (o) Yes   ( ) No The (o) and ( ) in this prototype represent radio buttons. My personal view is that if the question has only a true or false value then it should be a check box. That said, I have seen this sort of "layout" from almost every designer I've ever worked with. If I were not to question their decision, or question the client's decision, I'd probably mark it up like this: <p class="pseudo_label">Some long winded yes or no question?</p> <input type="radio" name="the_question" id="the_question_yes" value="1"> <label for="the_question_yes" class="after_radio">Yes</label> <input type="radio" name="the_question" id="the_question_no" value="0"> <label for="the_question_no" class="after_radio">No</label> I really don't want to do that. I want to push back and convince them that this should really be a check box and not two radio buttons. But my question is, if I can't convince them – you're welcome to help me try – how should I code that original design requirement such that it is semantic and at least understandable for screen reader users? If I were able to convince my tormentors to change their minds, I would likely code it in the following fashion: <label for="the_question">Some long winded yes or no question?</label> <input type="checkbox" name="the_question" id="the_question" value="1"> What do you think about this issue? Should I push back? Possibly more importantly is either way semantically correct? UPDATE: I have posted a related question on the UI SE per your suggestions. You can find it here: http://ui.stackexchange.com/q/3335/3493

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