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• On the search for my next great .Net Read

  - by user127954

  Just got done with "The art of unit testing". It was a great read and i think everyone should go buy a copy. With that said i think the next book I'm like to read would be a architecture / Design type book that would focus heavily on building your objects / software in such a way that it would be: Low Coupling High Cohesion Easily Maintainable / Extended Easy to test Easy to Navigate / Debug The above characteristcs are the most important ones but also maybe it would also include (but not necessary) designing for: Performance - Don't want to design a system at at the end find out its dog slow :) Scalability - Again don't want to design something at the end find out it won't scale. I'd also prefer (but not necessary again): Something newer - Architectural principles seem to gradually evolve / improve over time and id like something with current thinking. .Net as illustrating language - like i said above its not mandatory but since its what i use every day id prefer it to be in .net. Doesn't really matter if its in vb.net or c# Some of the topics that would be talked about its how to minimize dependencies and using interfaces throughout your solution rather than concrete classes. Maybe it would constract /compare some of the newest design principles like DDD, Repository Pattern, Ect... I already have "Clean Code" (don't know if its this type of book or not) and "Working effectively with legacy code" on my radar but id like to read a book based upon the topic i talked about above first. Is there such a book?

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• Using array of Action() in a lambda expression

  - by Sean87

  I want to do some performance measurement for a method that does some work with int arrays, so I wrote the following class: public class TimeKeeper { public TimeSpan Measure(Action[] actions) { var watch = new Stopwatch(); watch.Start(); foreach (var action in actions) { action(); } return watch.Elapsed; } } But I can not call the Measure mehotd for the example below: var elpased = new TimeKeeper(); elpased.Measure( () => new Action[] { FillArray(ref a, "a", 10000), FillArray(ref a, "a", 10000), FillArray(ref a, "a", 10000) }); I get the following errors: Cannot convert lambda expression to type 'System.Action[]' because it is not a delegate type Cannot implicitly convert type 'void' to 'System.Action' Cannot implicitly convert type 'void' to 'System.Action' Cannot implicitly convert type 'void' to 'System.Action' Here is the method that works with arrays: private void FillArray(ref int[] array, string name, int count) { array = new int[count]; for (int i = 0; i < array.Length; i++) { array[i] = i; } Console.WriteLine("Array {0} is now filled up with {1} values", name, count); } What I am doing wrong?

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• Saving tags into a database table in CakePHP

  - by Cameron

  I have the following setup for my CakePHP app: Posts id title content Topics id title Topic_Posts id topic_id post_id So basically I have a table of Topics (tags) that are all unique and have an id. And then they can be attached to post using the Topic_Posts join table. When a user creates a new post they will fill in the topics by typing them in to a textarea separated by a comma which will then save these into the Topics table if they do not already exist and then save the references into the Topic_posts table. I have the models set up like so: Post model: class Post extends AppModel { public $name = 'Post'; public $hasAndBelongsToMany = array( 'Topic' => array('with' => 'TopicPost') ); } Topic model: class Topic extends AppModel { public $hasMany = array( 'TopicPost' ); } TopicPost model: class TopicPost extends AppModel { public $belongsTo = array( 'Topic', 'Post' ); } And for the New post method I have this so far: public function add() { if ($this->request->is('post')) { //$this->Post->create(); if ($this->Post->saveAll($this->request->data)) { // Redirect the user to the newly created post (pass the slug for performance) $this->redirect(array('controller'=>'posts','action'=>'view','id'=>$this->Post->id)); } else { $this->Session->setFlash('Server broke!'); } } } As you can see I have used saveAll but how do I go about dealing with the Topic data?

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• Sql Server 2005 multiple insert with c#

  - by bottlenecked

  Hello. I have a class named Entry declared like this: class Entry{ string Id {get;set;} string Name {get;set;} } and then a method that will accept multiple such Entry objects for insertion into the database using ADO.NET: static void InsertEntries(IEnumerable<Entry> entries){ //build a SqlCommand object using(SqlCommand cmd = new SqlCommand()){ ... const string refcmdText = "INSERT INTO Entries (id, name) VALUES (@id{0},@name{0});"; int count = 0; string query = string.Empty; //build a large query foreach(var entry in entries){ query += string.Format(refcmdText, count); cmd.Parameters.AddWithValue(string.Format("@id{0}",count), entry.Id); cmd.Parameters.AddWithValue(string.Format("@name{0}",count), entry.Name); count++; } cmd.CommandText=query; //and then execute the command ... } } And my question is this: should I keep using the above way of sending multiple insert statements (build a giant string of insert statements and their parameters and send it over the network), or should I keep an open connection and send a single insert statement for each Entry like this: using(SqlCommand cmd = new SqlCommand(){ using(SqlConnection conn = new SqlConnection(){ //assign connection string and open connection ... cmd.Connection = conn; foreach(var entry in entries){ cmd.CommandText= "INSERT INTO Entries (id, name) VALUES (@id,@name);"; cmd.Parameters.AddWithValue("@id", entry.Id); cmd.Parameters.AddWithValue("@name", entry.Name); cmd.ExecuteNonQuery(); } } } What do you think? Will there be a performance difference in the Sql Server between the two? Are there any other consequences I should be aware of? Thank you for your time!

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• PHP modifying and combining array

  - by Industrial

  Hi everyone, I have a bit of an array headache going on. The function does what I want, but since I am not yet to well acquainted with PHP:s array/looping functions, so thereby my question is if there's any part of this function that could be improved from a performance-wise perspective? I tried to be as complete as possible in my descriptions in each stage of the functions which shortly described prefixes all keys in an array, fill up eventual empty/non-valid keys with '' and removes the prefixes before returning the array: $var = myFunction ( array('key1', 'key2', 'key3', '111') ); function myFunction ($keys) { $prefix = 'prefix_'; $keyCount = count($keys); // Prefix each key and remove old keys for($i=0;$i<$keyCount; $i++){ $keys[] = $prefix.$keys[$i]; unset($keys[$i]); } // output: array('prefix_key1', 'prefix_key2', 'prefix_key3', '111) // Get all keys from memcached. Only returns valid keys $items = $this->memcache->get($keys); // output: array('prefix_key1' => 'value1', 'prefix_key2' => 'value2', 'prefix_key3'=>'value3) // note: key 111 was not found in memcache. // Fill upp eventual keys that are not valid/empty from memcache $return = $items + array_fill_keys($keys, ''); // output: array('prefix_key1' => 'value1', 'prefix_key2' => 'value2', 'prefix_key3'=>'value3, 'prefix_111' => '') // Remove the prefixes for each result before returning array to application foreach ($return as $k => $v) { $expl = explode($prefix, $k); $return[$expl[1]] = $v; unset($return[$k]); } // output: array('key1' => 'value1', 'key2' => 'value2', 'key3'=>'value3, '111' => '') return $return; } Thanks a lot!

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• do the Python libraries have a natural dependence on the global namespace?

  - by msw

  I first ran into this when trying to determine the relative performance of two generators: t = timeit.repeat('g.get()', setup='g = my_generator()') So I dug into the timeit module and found that the setup and statement are evaluated with their own private, initially empty namespaces so naturally the binding of g never becomes accessible to the g.get() statement. The obvious solution is to wrap them into a class, thus adding to the global namespace. I bumped into this again when attempting, in another project, to use the multiprocessing module to divide a task among workers. I even bundled everything nicely into a class but unfortunately the call pool.apply_async(runmc, arg) fails with a PicklingError because buried inside the work object that runmc instantiates is (effectively) an assignment: self.predicate = lambda x, y: x > y so the whole object can't be (understandably) pickled and whereas: def foo(x, y): return x > y pickle.dumps(foo) is fine, the sequence bar = lambda x, y: x > y yields True from callable(bar) and from type(bar), but it Can't pickle <function <lambda> at 0xb759b764>: it's not found as __main__.<lambda>. I've given only code fragments because I can easily fix these cases by merely pulling them out into module or object level defs. The bug here appears to be in my understanding of the semantics of namespace use in general. If the nature of the language requires that I create more def statements I'll happily do so; I fear that I'm missing an essential concept though. Why is there such a strong reliance on the global namespace? Or, what am I failing to understand? Namespaces are one honking great idea -- let's do more of those!

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• Books for Computer Networking

  - by Altimet Gaandu

  Hi, I am a student of computer engineering from Vasula University, Somalia. We have a subject called Advanced Computer Networks and the following is the list of recommended books: Text Books: 1. B. A. Forouzan, "TCP/IP Protocol Suite", Tata McGraw Hill edition, Third Edition. 2. N. Olifer, V. Olifer, "Computer Networks: Principles, Technologies and Protocols for Network design", Wiley India Edition, First edition. References: 1. W.Richard Stevens, "TCP/IP Volume1, 2, 3", Addison Wesley. 2. D.E.Comer,"TCP/IPVolumeI and II", PearsonEducation. . 3.W.R. Stevens, "Unix Network Programming", Vol. 1, Pearson Education. 4. J.Walrand, P. Var~fya, "High Performance Communication Networks", Morgan Kaufmann. . 5. A.S.Tanenbaum,"Computer Networks", Pearson Education, Fourth Edition. But we have been unable to find these either in the market or on the internet (read: torrents). Please provide download links to any of these books and oblige. Thanks.

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• Round date to 10 minutes interval

  - by Peter Lang

  I have a DATE column that I want to round to the next-lower 10 minute interval in a query (see example below). I managed to do it by truncating the seconds and then subtracting the last digit of minutes. WITH test_data AS ( SELECT TO_DATE('2010-01-01 10:00:00', 'YYYY-MM-DD HH24:MI:SS') d FROM dual UNION SELECT TO_DATE('2010-01-01 10:05:00', 'YYYY-MM-DD HH24:MI:SS') d FROM dual UNION SELECT TO_DATE('2010-01-01 10:09:59', 'YYYY-MM-DD HH24:MI:SS') d FROM dual UNION SELECT TO_DATE('2010-01-01 10:10:00', 'YYYY-MM-DD HH24:MI:SS') d FROM dual UNION SELECT TO_DATE('2099-01-01 10:00:33', 'YYYY-MM-DD HH24:MI:SS') d FROM dual ) -- #end of test-data SELECT d, TRUNC(d, 'MI') - MOD(TO_CHAR(d, 'MI'), 10) / (24 * 60) FROM test_data And here is the result: 01.01.2010 10:00:00    01.01.2010 10:00:00 01.01.2010 10:05:00    01.01.2010 10:00:00 01.01.2010 10:09:59    01.01.2010 10:00:00 01.01.2010 10:10:00    01.01.2010 10:10:00 01.01.2099 10:00:33    01.01.2099 10:00:00 Works as expected, but is there a better way? EDIT: I was curious about performance, so I did the following test with 500.000 rows and (not really) random dates. I am going to add the results as comments to the provided solutions. DECLARE t TIMESTAMP := SYSTIMESTAMP; BEGIN FOR i IN ( WITH test_data AS ( SELECT SYSDATE + ROWNUM / 5000 d FROM dual CONNECT BY ROWNUM <= 500000 ) SELECT TRUNC(d, 'MI') - MOD(TO_CHAR(d, 'MI'), 10) / (24 * 60) FROM test_data ) LOOP NULL; END LOOP; dbms_output.put_line( SYSTIMESTAMP - t ); END; This approach took 03.24 s.

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• Best Functional Approach

  - by dbyrne

  I have some mutable scala code that I am trying to rewrite in a more functional style. It is a fairly intricate piece of code, so I am trying to refactor it in pieces. My first thought was this: def iterate(count:Int,d:MyComplexType) = { //Generate next value n //Process n causing some side effects return iterate(count - 1, n) } This didn't seem functional at all to me, since I still have side effects mixed throughout my code. My second thought was this: def generateStream(d:MyComplexType):Stream[MyComplexType] = { //Generate next value n return Stream.cons(n, generateStream(n)) } for (n <- generateStream(initialValue).take(2000000)) { //process n causing some side effects } This seemed like a better solution to me, because at least I've isolated my functional value-generation code from the mutable value-processing code. However, this is much less memory efficient because I am generating a large list that I don't really need to store. This leaves me with 3 choices: Write a tail-recursive function, bite the bullet and refactor the value-processing code Use a lazy list. This is not a memory sensitive app (although it is performance sensitive) Come up with a new approach. I guess what I really want is a lazily evaluated sequence where I can discard the values after I've processed them. Any suggestions?

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• Implement a threading to prevent UI block on a bug in an async function

  - by Marcx

  I think I ran up againt a bug in an async function... Precisely the getDirectoryListingAsync() of the File class... This method is supposted to return an object containing the lists of files in a specified folder. I found that calling this method on a direcory with a lot of files (in my tests more than 20k files), after few seconds there is a block on the UI until the process is completed... I think that this method is separated in two main block: 1) get the list of files 2) create the array with the details of the files The point 1 seems to be async (for a few second the ui is responsive), then when the process pass from point 1 to point 2 the block of the UI occurs until the complete event is dispathed... Here's some (simple) code: private function checkFiles(dir:File):void { if (dir.exists) { dir.addEventListener( FileListEvent.DIRECTORY_LISTING, listaImmaginiLocale); dir.getDirectoryListingAsync(); // after this point, for the firsts seconds the UI respond well (point 1), // few seconds later (point 2) the UI is frozen } } private function listaImmaginiLocale( event:FileListEvent ):void { // from this point on the UI is responsive again... } Actually in my projects there are some function that perform an heavy cpu usage and to prevent the UI block I implemented a simple function that after some iteration will wait giving time to UI to be refreshed. private var maxIteration:int = 150000; private function sampleFunct(offset:int = 0) :void { if (offset < maxIteration) { // do something // call the recursive function using a timeout.. // if the offset in multiple by 1000 the function will wait 15 millisec, // otherwise it will be called immediately // 1000 is a random number for the pourpose of this example, but I usually change the // value based on how much heavy is the function itself... setTimeout(function():void{aaa(++offset);}, (offset%1000?15:0)); } } Using this method I got a good responsive UI without afflicting performance... I'd like to implement it into the getDirectoryListingAsync method but I don't know if it's possibile how can I do it where is the file to edit or extend.. Any suggestion???

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• java.awt.Robot.keyPress for continuous keystrokes

  - by Deb

  So, here's my problem. I have a java program which will send keystroke messages to a game (built in Unity), based on how the user interacts with an android phone. (My java program is a listener for the android interaction over wi-fi) Now, in order to do this, I am using java.awt.Robot to send keyPresses to the game window. I have the following code block written in my listener program: if(interacting) { Robot robot = new Robot(); robot.keyPress(VK_A); robot.delay(20); //to simulate the normal keyboard rate } Now the variable interacting will be true as long as the user presses down on the touch screen of the phone, and what I intend to achieve is a continuous chain of keystroke messages being delivered to the game (through the listener). However, this is severely affecting performance, for some reason. I am noticing that the game becomes slow (rapidly dropping frame rates), and even the computer becomes slow, in general. What's going wrong? Should I use a robot.keyRelease(VK_A) after each keyPress? But my game has a different action mapped to the release of a key, and I do not want rapid key presses and releases; what I really want is to simulate continuous keystrokes, in exactly the way it would behave if the user were pressing down the A key on their keyboard manually. Please help.

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• Generating jquery 'rules' from business model to UI in asp.net mvc

  - by jim

  Hi all, I've had a good look around and am certain that there's no matching question on SO, so here goes. Has anyone created a 'helper' method on their model that generates jquery (or plain javascript) rules validation dynamically, based on the criteria/rules that are contained within the object and taken from a repository (i.e. DB). What i'm thinking of is a discrete set of partial views (and associated models) that have rules at the business logic 'level' and rather than (or in combination with) validating the rule(s) at postback, translating the same rules into tightly focussed jquery methods that work identically at client (js) and server (c#) levels. I can see benefits here re performance. Also, the rules definitions could be created in a single place (in c#) and the jquery generated off of that, thus allowing single edits to update both code streams. I appreciate that there would be limitations imposed by language specific contstraints but the general principle could be quite interesting if used appropriately. I'm also aware that testibility could be an issue when using two different language structures and hoping to achieve similar test outcomes - but those aside... any thoughts or experiences of similar out there?? cheers jimi

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• Approaches for animating a C# property over time?

  - by Mario Fritsch

  I'm currently trying to animate a bunch of public properties on certain objects. Usually they are of type float or vectors of floats (the type is known at compile-time). I want to be able to: assign a static value to them (MyObject.Duration = 10f;) or assign a random value to them by specifying a minimum and maximum value and optionally also a weight (MyObject.Duration = new RandomFloat(5f, 20f, 2f);) or "bind" this property to the property of another object (think of a child object binding some of its properties to its parent object, like its color or size or sth.) or assign sort of a keyframe animation to them, specifying a variable number of keyframes with timecode and the property's value at that specific point in time as well as information about how to interpolate between these frames The keyframes should be able to accept random values for each frame, both for the time and the property's value. What would be a practical approach for this kind of system? Currently I'm thinking about polymorphism: implement a base class or interface with a public Value-property and/or GetValue(float time)-method and then creating different sub classes like StaticValue, RandomValue, BindingValue and AnimatedValue implementing this base class or interface. Doesn't seem very elegant, though, and the initialization of even simple objects becomes a bit tedious. Another idea would be to implement these properties just as regular floats or vectors and create special "Modifier"-types binding to these properties. To retrieve the "real" value of the property, I'd first call any Modifier bound to the property, which would in turn update the actual object's property for me to retrieve later on. That would most likely mean using reflection at some point, which could be quite bad for performance as I'll probably have thousands of properties to update dozens of times per second. Any suggestions on this? Being a novice I'm (hopefully) missing some far more elegant and/or practical solution than I'm already playing around with :( Edit: Probably should have mentioned this earlier, but WPF isn't an option - it's not available on all targetted platforms, so I can't rely on it. I'm aware of its powerful databinding and animation capabilities, but I need to roll my own (or find some other lightweight alternative meeting my needs).

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• What's so bad about building XML with string concatenation?

  - by wsanville

  In the thread What’s your favorite “programmer ignorance” pet peeve?, the following answer appears, with a large amount of upvotes: Programmers who build XML using string concatenation. My question is, why is building XML via string concatenation (such as a StringBuilder in C#) bad? I've done this several times in the past, as it's sometimes the quickest way for me to get from point A to point B when to comes to the data structures/objects I'm working with. So far, I have come up with a few reasons why this isn't the greatest approach, but is there something I'm overlooking? Why should this be avoided? Probably the biggest reason I can think of is you need to escape your strings manually, and most programmers will forget this. It will work great for them when they test it, but then "randomly" their apps will fail when someone throws an & symbol in their input somewhere. Ok, I'll buy this, but it's really easy to prevent the problem (SecurityElement.Escape to name one). When I do this, I usually omit the XML declaration (i.e. <?xml version="1.0"?>). Is this harmful? Performance penalties? If you stick with proper string concatenation (i.e. StringBuilder), is this anything to be concerned about? Presumably, a class like XmlWriter will also need to do a bit of string manipulation... There are more elegant ways of generating XML, such as using XmlSerializer to automatically serialize/deserialize your classes. Ok sure, I agree. C# has a ton of useful classes for this, but sometimes I don't want to make a class for something really quick, like writing out a log file or something. Is this just me being lazy? If I am doing something "real" this is my preferred approach for dealing w/ XML.

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• Database layout for an application with geocoding features using geokit

  - by vooD

  I'm developing a real estate web catalogue and want to geocode every ad using geokit gem. My question is what would be the best database layout from the performance point if i want to make search by country, city of the selected country, administrative area or nearest metro station of the selected city. Available countries, cities, administrative areas and metro sations should be defined by the administrator of catalogue and must be validated by geocoding. I came up with single table: create_table "geo_locations", :force => true do |t| t.integer "geo_location_id" #parent geo location (ex. country is parent geo location of city t.string "country", :null => false #necessary for any geo location t.string "city", #not null for city geo location and it's children t.string "administrative_area" #not null for administrative_area geo location and it's children t.string "thoroughfare_name" #not null for metro station or street name geo location and it's children t.string "premise_number" #house number t.float "lng", :null => false t.float "lat", :null => false t.float "bound_sw_lat", :null => false t.float "bound_sw_lng", :null => false t.float "bound_ne_lat", :null => false t.float "bound_ne_lng", :null => false t.integer "mappable_id" t.string "mappable_type" t.string "type" #country, city, administrative area, metro station or address end Final geo location is address it contains all neccessary information to put marker of the real estate ad on the map. But i'm still stuck on search functionality. Any help would be highly appreciated.

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• Obfuscator for .NET assembly (Maybe just a C++ obfuscator?)

  - by Pirate for Profit

  The software company I work for is using a ton of open source LGPL/BSD/MIT C++ code that we have written wrappers around to port "helper classes" into a .NET assembly, via C++/CLI. These libraries have wrapped old cryptic APIs into easy-to-use ones based on common sense, and will be very helpful for a lot of different tasks will be included in many future client's applications, and we might even license it to other software companies in the same field. So naturally we are tasked with looking into solutions for securing the code from prying eyes. What we're trying to do is stop the casual observer from seeing what's going on. Now I have hacked some crazy shit in EverQuest and other video games in my day so I know with enough tireless effort anything can be done. But we don't want to make it easy for whomever. To the point, besides the Visual Studio compiler's optimizations, is there's a C++ obfuscator or .NET assembly obfuscator (after it's been built o.O) or something that would scramble everything up, re-arrange data structures, string constants, etc. idk? And if such a thing exists, we'd be curious to know how that would impact performance, as some sections of code are time critical (funny saying that using a managed M$ framework).

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• How to get a debug flow of execution in C++

  - by Rich

  Hi, I work on a global trading system which supports many users. Each user can book,amend,edit,delete trades. The system is regulated by a central deal capture service. The deal capture service informs all the user of any updates that occur. The problem comes when we have crashes, as the production environment is impossible to re-create on a test system, I have to rely on crash dumps and log files. However this doesn't tell me what the user has been doing. I'd like a system that would (at the time of crashing) dump out a history of what the user has been doing. Anything that I add has to go into the live environment so it can't impact performance too much. Ideas wise I was thinking of a MACRO at the top of each function which acted like a stack trace (only I could supply additional user information, like trade id's, user dialog choices, etc ..) The system would record stack traces (on a per thread basis) and keep a history in a cyclic buffer (varying in size, depending on how much history you wanted to capture). Then on crash, I could dump this history stack. I'd really like to hear if anyone has a better solution, or if anyone knows of an existing framework? Thanks Rich

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• Updating UI objects in windows forms

  - by P a u l

  Pre .net I was using MFC, ON_UPDATE_COMMAND_UI, and the CCmdUI class to update the state of my windows UI. From the older MFC/Win32 reference: Typically, menu items and toolbar buttons have more than one state. For example, a menu item is grayed (dimmed) if it is unavailable in the present context. Menu items can also be checked or unchecked. A toolbar button can also be disabled if unavailable, or it can be checked. Who updates the state of these items as program conditions change? Logically, if a menu item generates a command that is handled by, say, a document, it makes sense to have the document update the menu item. The document probably contains the information on which the update is based. If a command has multiple user-interface objects (perhaps a menu item and a toolbar button), both are routed to the same handler function. This encapsulates your user-interface update code for all of the equivalent user-interface objects in a single place. The framework provides a convenient interface for automatically updating user-interface objects. You can choose to do the updating in some other way, but the interface provided is efficient and easy to use. What is the guidance for .net Windows Forms? I am using an Application.Idle handler in the main form but am not sure this is the best way to do this. About the time I put all my UI updates in the Idle event handler my app started to show some performance problems, and I don't have the metrics to track this down yet. Not sure if it's related.

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• Approach for caching data from data logger

  - by filip-fku

  Greetings, I've been working on a C#.NET app that interacts with a data logger. The user can query and obtain logs for a specified time period, and view plots of the data. Typically a new data log is created every minute and stores a measurement for a few parameters. To get meaningful information out of the logger, a reasonable number of logs need to be acquired - data for at least a few days. The hardware interface is a UART to USB module on the device, which restricts transfers to a maximum of about 30 logs/second. This becomes quite slow when reading in the data acquired over a number of days/weeks. What I would like to do is improve the perceived performance for the user. I realize that with the hardware speed limitation the user will have to wait for the full download cycle at least the first time they acquire a larger set of data. My goal is to cache all data seen by the app, so that it can be obtained faster if ever requested again. The approach I have been considering is to use a light database, like SqlServerCe, that can store the data logs as they are received. I am then hoping to first search the cache prior to querying a device for logs. The cache would be updated with any logs obtained by the request that were not already cached. Finally my question - would you consider this to be a good approach? Are there any better alternatives you can think of? I've tried to search SO and Google for reinforcement of the idea, but I mostly run into discussions of web request/content caching. Thanks for any feedback!

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• Problem with incomplete input when using Attoparsec

  - by Dan Dyer

  I am converting some functioning Haskell code that uses Parsec to instead use Attoparsec in the hope of getting better performance. I have made the changes and everything compiles but my parser does not work correctly. I am parsing a file that consists of various record types, one per line. Each of my individual functions for parsing a record or comment works correctly but when I try to write a function to compile a sequence of records the parser always returns a partial result because it is expecting more input. These are the two main variations that I've tried. Both have the same problem. items :: Parser [Item] items = sepBy (comment <|> recordType1 <|> recordType2) endOfLine For this second one I changed the record/comment parsers to consume the end-of-line characters. items :: Parser [Item] items = manyTill (comment <|> recordType1 <|> recordType2) endOfInput Is there anything wrong with my approach? Is there some other way to achieve what I am attempting?

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• best web database solution for scala for a high traffic site?

  - by egervari

  I am in charge of a rebuilding a website that gets about 250,000 visitors a day. We'd like to use Scala, but it does not work very well with Spring (in some minor cases) and Hibernate (there is a major and very annoying mismatch here if you want to use scala collections, which we do). The application itself is going to have about 40-50 tables. Other than Hibernate, is there an ORM that works awesome with Scala and is as performant and reliable as Hibernate? Does it also have the same capabilities, or are we going to run into leaky-abstractions if we don't use Hibernate? It would be a big risk for us to go with a framework that is newer and doesn't seem to have a lot of industry backing... and at the same time, Hibernate is a real pain to program against when using Scala. 1) The Java Collection <- Scala Collection is absolutely painful. There is a lot more boilerplate and crap to write. 2) The IDE doesn't import JavaConversions and java interfaces automatically... so we this needs to be done manually. Optimizing Imports in IDEA is going to destroy all the manual work. 3) There is also a performance cost to converting back and forth all the time in your domain objects and your dao classes. 4) Not to mention there needs to be a lot of casting, which produces code ugly as sin. I actually would love to write my own orm that is 100% tailored to scala, but obviously this is really outside of the scope of our project for now. So what is the best approach?

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• Is locking on the requested object a bad idea?

  - by Quick Joe Smith

  Most advice on thread safety involves some variation of the following pattern: public class Thing { private static readonly object padlock = new object(); private string stuff, andNonsense; public string Stuff { get { lock (Thing.padlock) { if (this.stuff == null) this.stuff = "Threadsafe!"; } return this.stuff; } } public string AndNonsense { get { lock (Thing.padlock) { if (this.andNonsense == null) this.andNonsense = "Also threadsafe!"; } return this.andNonsense; } } // Rest of class... } In cases where the get operations are expensive and unrelated, a single locking object is unsuitable because a call to Stuff would block all calls to AndNonsense, degrading performance. And rather than create a lock object for each call, wouldn't it be better to acquire the lock on the member itself (assuming it is not something that implements SyncRoot or somesuch for that purpose? For example: public string Stuff { get { lock (this.stuff) { // Pretend that this is a very expensive operation. if (this.stuff == null) this.stuff = "Still threadsafe and good?"; } return this.stuff; } } Strangely, I have never seen this approach recommended or warned against. Am I missing something obvious?

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• The correct usage of nested #pragma omp for directives

  - by GoldenLee

  The following code runs like a charm before OpenMP parallelization was applied. In fact, the following code was in a state of endless loop! I'm sure that's result from my incorrect use to the OpenMP directives. Would you please show me the correct way? Thank you very much. #pragma omp parallel for for (int nY = nYTop; nY <= nYBottom; nY++) { for (int nX = nXLeft; nX <= nXRight; nX++) { // Use look-up table for performance dLon = theApp.m_LonLatLUT.LonGrid()[nY][nX] + m_FavoriteSVISSRParams.m_dNadirLon; dLat = theApp.m_LonLatLUT.LatGrid()[nY][nX]; // If you don't want to use longitude/latitude look-up table, uncomment the following line //NOMGeoLocate.XYToGEO(dLon, dLat, nX, nY); if (dLon > 180 || dLat > 180) { continue; } if (Navigation.GeoToXY(dX, dY, dLon, dLat, 0) > 0) { continue; } // Skip void data scanline dY = dY - nScanlineOffset; // Compute coefficients as well as its four neighboring points' values nX1 = int(dX); nX2 = nX1 + 1; nY1 = int(dY); nY2 = nY1 + 1; dCx = dX - nX1; dCy = dY - nY1; dP1 = pIRChannelData->operator [](nY1)[nX1]; dP2 = pIRChannelData->operator [](nY1)[nX2]; dP3 = pIRChannelData->operator [](nY2)[nX1]; dP4 = pIRChannelData->operator [](nY2)[nX2]; // Bilinear interpolation usNomDataBlock[nY][nX] = (unsigned short)BilinearInterpolation(dCx, dCy, dP1, dP2, dP3, dP4); } }

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• Using Lucene to index private data, should I have a separate index for each user or a single index

  - by Nathan Bayles

  I am developing an Azure based website and I want to provide search capabilities using Lucene. (structured json objects would be indexed and stored in Lucene and other content such as Word documents, etc. would be indexed in lucene but stored in blob storage) I want the search to be secure, such that one user would never see a document belonging to another user. I want to allow ad-hoc searches as typed by the user. Lastly, I want to query programmatically to return predefined sets of data, such as "all notes for user X". I think I understand how to add properties to each document to achieve these 3 objectives. (I am listing them here so if anyone is kind enough to answer, they will have better idea of what I am trying to do) My questions revolve around performance and security. Can I improve document security by having a separate index for each user, or is including the user's ID as a parameter in each search sufficient? Can I improve indexing speed and total throughput of the system by having a separate index for each user? My thinking is that having separate indexes would allow me to scale the system by having multiple index writers (perhaps even on different server instances) working at the same time, each on their own index. Any insight would be greatly appreciated. Regards, Nate

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• Android opengl releasing textures

  - by user1642418

  I have a bit of a problem. I am developing a game for android + engine and I got stuck. I am getting OpenGL out of memory error and either app crashes or phone hangs after loading a scene multiple times. For example: app launches, shows main menu, 1st level/scene is loaded. Then I go back to main menu, and repeat. It doesnt matter which scene I load, after 4-6 times the error occurs. Some background: Each time when scene is loaded all the resources are released and upon first frame render - needed stuff gets loaded. The performance is more or less ok. Note that I am calling glDeleteTexture method, but I think its not doing its job and releasing memory. Thing is that -when I minimize and open it again - problem doesn't occur, but almost the same things are executed. Problem doesn't occur. This way android releases memory. How do I release/get rid of unused textures properly? This happens on HTC Desire HD ( ice cream sandwich 4.0.4) . Other games works fine, so I bet this is not the problem in ROM.

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