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  • Using machine learning to aim mirrors in a solar array?

    - by Buttons840
    I've been thinking about solar collectors where several independent mirrors to focus the light on a solar collector, similar to the following design from Energy Innovations. Because there will be flaws in the assembly of this solar array, I am proceeding with the following assumptions (or lack thereof): The software knows the "position" of each mirror, but doesn't know how this position relates to the real world or to other mirrors. This will account for poor mirror calibration or other environmental factors which may effect one mirror but not the others. If a mirror moves 10 units in one direction, and then 10 units in the opposite direction, it will end up where it originally started. I would like to use machine learning to position the mirrors correctly and focus the light on the collector. I expect I would approach this as an optimization problem, optimizing the mirror positions to maximize the heat inside the collector and the power output. The problem is finding a small target in a noisy high-dimensional space (considering each mirror has 2 axis of rotation). Some of the problems I anticipate are: cloudy days, even if you stumble upon the perfect mirror alignment, it might be cloudy at the time noisy sensor data the sun is a moving target, it moves along a path, and follows a different path every day - although you could calculate the exact position of the sun at any time, you wouldn't know how that position relates to your mirrors My question isn't about the solar array, but possible machine learning techniques that would help in this "small target in a noisy high dimensional-space" problem. I mentioned the solar array because it was the catalyst for this question and a good example. What machine learning techniques can find such a small target in a noisy high-dimensional space? EDIT: A few additional thoughts: Yes, you can calculate the suns position in the real world, but you don't know how the mirrors position is related to the real world (unless you've learned it somehow). You might know the suns azimuth is 220 degrees, and the suns elevation is 60 degrees, and you might know a mirror is at position (-20, 42); now tell me, is that mirror correctly aligned with the sun? You don't know. Lets assume you have some very sophisticated heat measurements, and you know "with this heat level, there must be 2 mirrors correctly aligned". Now the question is, which two mirrors (out of 25 or more) are correctly aligned? One solution I considered was to approximate the correct "alignment function" using a neural network which would take the suns azimuth and elevation as input and output a large array with 2 values for each mirror which correspond to the 2 axis of each mirror. I'm not sure what the best training method is though.

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  • How to actually defragment a JFFS2 filesystem

    - by Julie in Austin
    I have searched all over the Internet, including on a number of StackExchange forums, for a workable method for defragmenting a JFFS2 filesystem and cannot find an answer. The system in question has a 256MB NAND flash part. It is being accessed as a MTD device which is divided into three partitions. The third partition is where the root file system is being stored as a JFFS2 file system. The issue is that writes to the root file system have non-deterministic performance due to the usual issues of the JFFS2 garbage collector deciding to run at the worst possible times. When that happens, the product is hung for some unknown length of time while the garbage collector (and pdflush) run. Changing the file system isn't an option. The solution needs to be something that can run during off-hours that after having been run results in more predictable write performance. Right now I am working on a program that will attempt to force the garbage collector to run, then delete the file with the hope that all of the freed nodes are suddenly more readily available and make writes perform better. Thoughts?

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  • Apache multiple vhost logs, stored locally and sent to remote logstash

    - by benbradley
    I'm investigating centralised logging and it seems there's so many different ways this can be done. I don't want to run logstash as a log "sender", preferring to keep the web servers as lean and simple possible. So that means either using syslog, syslog-ng or the one I'm testing now, rsyslog. But I would like to have separate vhost log files on the web server, in addition to these logs being sent to a remote log collector. I've tested rsyslog using the imfile module to watch the Apache log files, but this means I have to hard-code each vhost log file into my rsyslog.conf. Not ideal as people will invariably forget when they add/remove sites on the server. The reason I'm using rsyslog's imfile is that Apache doesn't appear to let you log to file and syslog. And I want to keep vhost-specific log files on the web server. So how can I do this? Is there a way of having rsyslog produce local log files and forward the logs to a remote collector? I am prepared to change my Apache config to log to a single access/error log for all vhosts, so long as there are vhost-specific log files produced somewhere on the web server machine. I just don't want to lose any logging info if the remote log collector can't be contacted for any reason. Any comments/suggestions? Cheers, B

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  • can not access MovieClip properties in flashDevelop

    - by numerical25
    I know there is something I am doing wrong. In my controls I have keydown events that control my hero. As of right now, I am trying to rotate my hero but he refuses to turn . Below is my Hero Class, my control class, and gameobject class. pretty much all the classes associate with the controls class. package com.Objects { import com.Objects.GameObject; /** * ... * @author Anthony Gordon */ [Embed(source='../../../bin/Assets.swf', symbol='OuterRim')] public class Hero extends GameObject { public function Hero() { } } } Here is my Controls class. This is the class where I am trying to rotate my hero but he doesnt. The keydown event does work cause I trace it. package com.Objects { import com.Objects.Hero; import flash.events.*; import flash.display.MovieClip; /** * ... * @author Anthony Gordon */ public class Controls extends GameObject { private var aKeyPress:Array; public var ship:Hero; public function Controls(ship:Hero) { this.ship = ship; IsDisplay = false; aKeyPress = new Array(); engine.sr.addEventListener(KeyboardEvent.KEY_DOWN, keyDownListener); engine.sr.addEventListener(KeyboardEvent.KEY_UP,keyUpListener); } private function keyDownListener(e:KeyboardEvent):void { //trace("down e.keyCode=" + e.keyCode); aKeyPress[e.keyCode] = true; trace(e.keyCode); } private function keyUpListener(e:KeyboardEvent):void { //trace("up e.keyCode=" + e.keyCode); aKeyPress[e.keyCode]=false; } override public function UpdateObject():void { Update(); } private function Update():void { if (aKeyPress[37])//Key press left ship.rotation += 3,trace(ship.rotation ); ///DOESNT ROtate }//End Controls } } Here is GameObject Class package com.Objects { import com.Objects.Engine; import com.Objects.IGameObject; import flash.display.MovieClip; /** * ... * @author Anthony Gordon */ public class GameObject extends MovieClip implements IGameObject { private var isdisplay:Boolean = true; private var garbage:Boolean; public static var engine:Engine; public var layer:Number = 0; public function GameObject() { } public function UpdateObject():void { } public function GarbageCollection():void { } public function set Garbage(garb:Boolean):void { garbage = garb; } public function get Garbage():Boolean { return garbage } public function get IsDisplay():Boolean { return isdisplay; } public function set IsDisplay(display:Boolean):void { isdisplay = display; } public function set Layer(l:Number):void { layer = l; } public function get Layer():Number { return layer } } }

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  • exchange server 2010 with multiple domains

    - by air
    i have one exchange server 2010, which is working fine with one domain. my exchange is working as follows pop3 collector collect emails from one master catchall account and then deliver to exchange server, this working perfect. now what i want to add another domain to same exchange, i have added new domain as trusted domain & email policy and this new domain email account works fine with internal emails. now what i have done, i again forward new email account to same catchall account. but if i send email from any other external email address email is bounce, i can see email receive by pop3 collector but bounce by exchange server. to make you more clear let me explain logic on which i am working. i have 2 domains 1. domain1.com ([email protected]) 2. domain2.com ([email protected] -->[email protected]) now on my machine with exchange server i have pop3 collector which collect all emails from [email protected] and forward to exchange 2010 server. all emails to domain1.com is working perfect but when i send email to [email protected] this email redirect to [email protected] perfectly but when exchanger server receive this email, it bounce. i have also study the url link text and follow the whole process but no success. i also check that my DNS/MX is working fine as the bounce message is going from my exchange server. EDIT the only problem is with accepted domain, as email come to exchange server then bounce back. i just try this today i create one user called test, then i goto his properties -- email there was only one email account [email protected] i try to send email to [email protected] from internet (email bounce) then again i go to test user properties -- email and Add one email [email protected] again u try to send email to t*[email protected]* from internet (email received) i think the only problem is with accepted domain but in hub transport , it shows accepted is there any way to check does domain is properly accepted or not in exchange 2010 server. Thanks

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  • Clever memory usage through the years

    - by Ben Emmett
    A friend and I were recently talking about the really clever tricks people have used to get the most out of memory. I thought I’d share my favorites, and would love to hear yours too! Interleaving on drum memory Back in the ye olde days before I’d been born (we’re talking the 50s / 60s here), working memory commonly took the form of rotating magnetic drums. These would spin at a constant speed, and a fixed head would read from memory when the correct part of the drum passed it by, a bit like a primitive platter disk. Because each revolution took a few milliseconds, programmers took to manually arranging information non-sequentially on the drum, timing when an instruction or memory address would need to be accessed, then spacing information accordingly around the edge of the drum, thus reducing the access delay. Similar techniques were still used on hard disks and floppy disks into the 90s, but have become irrelevant with modern disk technologies. The Hashlife algorithm Conway’s Game of Life has attracted numerous implementations over the years, but Bill Gosper’s Hashlife algorithm is particularly impressive. Taking advantage of the repetitive nature of many cellular automata, it uses a quadtree structure to store the hashes of pieces of the overall grid. Over time there are fewer and fewer new structures which need to be evaluated, so it starts to run faster with larger grids, drastically outperforming other algorithms both in terms of speed and the size of grid which can be simulated. The actual amount of memory used is huge, but it’s used in a clever way, so makes the list . Elite’s procedural generation Ok, so this isn’t exactly a memory optimization – more a storage optimization – but it gets an honorable mention anyway. When writing Elite, David Braben and Ian Bell wanted to build a rich world which gamers could explore, but their 22K memory was something of a limitation (for comparison that’s about the size of my avatar picture at the top of this page). They procedurally generated all the characteristics of the 2048 planets in their virtual universe, including the names, which were stitched together using a lookup table of parts of names. In fact the original plans were for 2^52 planets, but it was decided that that was probably too many. Oh, and they did that all in assembly language. Other games of the time used similar techniques too – The Sentinel’s landscape generation algorithm being another example. Modern Garbage Collectors Garbage collection in managed languages like Java and .NET ensures that most of the time, developers stop needing to care about how they use and clean up memory as the garbage collector handles it automatically. Achieving this without killing performance is a near-miraculous feet of software engineering. Much like when learning chemistry, you find that every time you think you understand how the garbage collector works, it turns out to be a mere simplification; that there are yet more complexities and heuristics to help it run efficiently. Of course introducing memory problems is still possible (and there are tools like our memory profiler to help if that happens to you) but they’re much, much rarer. A cautionary note In the examples above, there were good and well understood reasons for the optimizations, but cunningly optimized code has usually had to trade away readability and maintainability to achieve its gains. Trying to optimize memory usage without being pretty confident that there’s actually a problem is doing it wrong. So what have I missed? Tell me about the ingenious (or stupid) tricks you’ve seen people use. Ben

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  • Leveraging Logical Standby Databases in Oracle 11g Data Guard

    Oracle Data Guard still offers support for the venerable logical standby database in Oracle Database 11g. This article, investigates how data warehouse and data mart environments can effectively leverage logical standby database features, but simultaneously provide a final destination when failover from a primary database is mandated during disaster recovery.

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  • Load and Web Performance Testing using Visual Studio Ultimate 2010-Part 3

    - by Tarun Arora
    Welcome back once again, in Part 1 of Load and Web Performance Testing using Visual Studio 2010 I talked about why Performance Testing the application is important, the test tools available in Visual Studio Ultimate 2010 and various test rig topologies, in Part 2 of Load and Web Performance Testing using Visual Studio 2010 I discussed the details of web performance & load tests as well as why it’s important to follow a goal based pattern while performance testing your application. In part 3 I’ll be discussing Test Result Analysis, Test Result Drill through, Test Report Generation, Test Run Comparison, Asp.net Profiler and some closing thoughts. Test Results – I see some creepy worms! In Part 2 we put together a web performance test and a load test, lets run the test to see load test to see how the Web site responds to the load simulation. While the load test is running you will be able to see close to real time analysis in the Load Test Analyser window. You can use the Load Test Analyser to conduct load test analysis in three ways: Monitor a running load test - A condensed set of the performance counter data is maintained in memory. To prevent the results memory requirements from growing unbounded, up to 200 samples for each performance counter are maintained. This includes 100 evenly spaced samples that span the current elapsed time of the run and the most recent 100 samples.         After the load test run is completed - The test controller spools all collected performance counter data to a database while the test is running. Additional data, such as timing details and error details, is loaded into the database when the test completes. The performance data for a completed test is loaded from the database and analysed by the Load Test Analyser. Below you can see a screen shot of the summary view, this provides key results in a format that is compact and easy to read. You can also print the load test summary, this is generated after the test has completed or been stopped.         Analyse the load test results of a previously run load test – We’ll see this in the section where i discuss comparison between two test runs. The performance counters can be plotted on the graphs. You also have the option to highlight a selected part of the test and view details, drill down to the user activity chart where you can hover over to see more details of the test run.   Generate Report => Test Run Comparisons The level of reports you can generate using the Load Test Analyser is astonishing. You have the option to create excel reports and conduct side by side analysis of two test results or to track trend analysis. The tools also allows you to export the graph data either to MS Excel or to a CSV file. You can view the ASP.NET profiler report to conduct further analysis as well. View Data and Diagnostic Attachments opens the Choose Diagnostic Data Adapter Attachment dialog box to select an adapter to analyse the result type. For example, you can select an IntelliTrace adapter, click OK and open the IntelliTrace summary for the test agent that was used in the load test.   Compare results This creates a set of reports that compares the data from two load test results using tables and bar charts. I have taken these screen shots from the MSDN documentation, I would highly recommend exploring the wealth of knowledge available on MSDN. Leaving Thoughts While load testing the application with an excessive load for a longer duration of time, i managed to bring the IIS to its knees by piling up a huge queue of requests waiting to be processed. This clearly means that the IIS had run out of threads as all the threads were busy processing existing request, one easy way of fixing this is by increasing the default number of allocated threads, but this might escalate the problem. The better suggestion is to try and drill down to the actual root cause of the problem. When ever the garbage collection runs it stops processing any pages so all requests that come in during that period are queued up, but realistically the garbage collection completes in fraction of a a second. To understand this better lets look at the .net heap, it is divided into large heap and small heap, anything greater than 85kB in size will be allocated to the Large object heap, the Large object heap is non compacting and remember large objects are expensive to move around, so if you are allocating something in the large object heap, make sure that you really need it! The small object heap on the other hand is divided into generations, so all objects that are supposed to be short-lived are suppose to live in Gen-0 and the long living objects eventually move to Gen-2 as garbage collection goes through.  As you can see in the picture below all < 85 KB size objects are first assigned to Gen-0, when Gen-0 fills up and a new object comes in and finds Gen-0 full, the garbage collection process is started, the process checks for all the dead objects and assigns them as the valid candidate for deletion to free up memory and promotes all the remaining objects in Gen-0 to Gen-1. So in the future when ever you clean up Gen-1 you have to clean up Gen-0 as well. When you fill up Gen – 0 again, all of Gen – 1 dead objects are drenched and rest are moved to Gen-2 and Gen-0 objects are moved to Gen-1 to free up Gen-0, but by this time your Garbage collection process has started to take much more time than it usually takes. Now as I mentioned earlier when garbage collection is being run all page requests that come in during that period are queued up. Does this explain why possibly page requests are getting queued up, apart from this it could also be the case that you are waiting for a long running database process to complete.      Lets explore the heap a bit more… What is really a case of crisis is when the objects are living long enough to make it to Gen-2 and then dying, this is definitely a high cost operation. But sometimes you need objects in memory, for example when you cache data you hold on to the objects because you need to use them right across the user session, which is acceptable. But if you wanted to see what extreme caching can do to your server then write a simple application that chucks in a lot of data in cache, run a load test over it for about 10-15 minutes, forcing a lot of data in memory causing the heap to run out of memory. If you get to such a state where you start running out of memory the IIS as a mode of recovery restarts the worker process. It is great way to free up all your memory in the heap but this would clear the cache. The problem with this is if the customer had 10 items in their shopping basket and that data was stored in the application cache, the user basket will now be empty forcing them either to get frustrated and go to a competitor website or if the customer is really patient, give it another try! How can you address this, well two ways of addressing this; 1. Workaround – A x86 bit processor only allows a maximum of 4GB of RAM, this means the machine effectively has around 3.4 GB of RAM available, the OS needs about 1.5 GB of RAM to run efficiently, the IIS and .net framework also need their share of memory, leaving you a heap of around 800 MB to play with. Because Team builds by default build your application in ‘Compile as any mode’ it means the application is build such that it will run in x86 bit mode if run on a x86 bit processor and run in a x64 bit mode if run on a x64 but processor. The problem with this is not all applications are really x64 bit compatible specially if you are using com objects or external libraries. So, as a quick win if you compiled your application in x86 bit mode by changing the compile as any selection to compile as x86 in the team build, you will be able to run your application on a x64 bit machine in x86 bit mode (WOW – By running Windows on Windows) and what that means is, you could use 8GB+ worth of RAM, if you take away everything else your application will roughly get a heap size of at least 4 GB to play with, which is immense. If you need a heap size of more than 4 GB you have either build a software for NASA or there is something fundamentally wrong in your application. 2. Solution – Now that you have put a workaround in place the IIS will not restart the worker process that regularly, which means you can take a breather and start working to get to the root cause of this memory leak. But this begs a question “How do I Identify possible memory leaks in my application?” Well i won’t say that there is one single tool that can tell you where the memory leak is, but trust me, ‘Performance Profiling’ is a great start point, it definitely gets you started in the right direction, let’s have a look at how. Performance Wizard - Start the Performance Wizard and select Instrumentation, this lets you measure function call counts and timings. Before running the performance session right click the performance session settings and chose properties from the context menu to bring up the Performance session properties page and as shown in the screen shot below, check the check boxes in the group ‘.NET memory profiling collection’ namely ‘Collect .NET object allocation information’ and ‘Also collect the .NET Object lifetime information’.    Now if you fire off the profiling session on your pages you will notice that the results allows you to view ‘Object Lifetime’ which shows you the number of objects that made it to Gen-0, Gen-1, Gen-2, Large heap, etc. Another great feature about the profile is that if your application has > 5% cases where objects die right after making to the Gen-2 storage a threshold alert is generated to alert you. Since you have the option to also view the most expensive methods and by capturing the IntelliTrace data you can drill in to narrow down to the line of code that is the root cause of the problem. Well now that we have seen how crucial memory management is and how easy Visual Studio Ultimate 2010 makes it for us to identify and reproduce the problem with the best of breed tools in the product. Caching One of the main ways to improve performance is Caching. Which basically means you tell the web server that instead of going to the database for each request you keep the data in the webserver and when the user asks for it you serve it from the webserver itself. BUT that can have consequences! Let’s look at some code, trust me caching code is not very intuitive, I define a cache key for almost all searches made through the common search page and cache the results. The approach works fine, first time i get the data from the database and second time data is served from the cache, significant performance improvement, EXCEPT when two users try to do the same operation and run into each other. But it is easy to handle this by adding the lock as you can see in the snippet below. So, as long as a user comes in and finds that the cache is empty, the user locks and starts to get the cache no more concurrency issues. But lets say you are processing 10 requests per second, by the time i have locked the operation to get the results from the database, 9 other users came in and found that the cache key is null so after i have come out and populated the cache they will still go in to get the results again. The application will still be faster because the next set of 10 users and so on would continue to get data from the cache. BUT if we added another null check after locking to build the cache and before actual call to the db then the 9 users who follow me would not make the extra trip to the database at all and that would really increase the performance, but didn’t i say that the code won’t be very intuitive, may be you should leave a comment you don’t want another developer to come in and think what a fresher why is he checking for the cache key null twice !!! The downside of caching is, you are storing the data outside of the database and the data could be wrong because the updates applied to the database would make the data cached at the web server out of sync. So, how do you invalidate the cache? Well if you only had one way of updating the data lets say only one entry point to the data update you can write some logic to say that every time new data is entered set the cache object to null. But this approach will not work as soon as you have several ways of feeding data to the system or your system is scaled out across a farm of web servers. The perfect solution to this is Micro Caching which means you cache the query for a set time duration and invalidate the cache after that set duration. The advantage is every time the user queries for that data with in the time span for which you have cached the results there are no calls made to the database and the data is served right from the server which makes the response immensely quick. Now figuring out the appropriate time span for which you micro cache the query results really depends on the application. Lets say your website gets 10 requests per second, if you retain the cache results for even 1 minute you will have immense performance gains. You would reduce 90% hits to the database for searching. Ever wondered why when you go to e-bookers.com or xpedia.com or yatra.com to book a flight and you click on the book button because the fare seems too exciting and you get an error message telling you that the fare is not valid any more. Yes, exactly => That is a cache failure! These travel sites or price compare engines are not going to hit the database every time you hit the compare button instead the results will be served from the cache, because the query results are micro cached, its a perfect trade-off, by micro caching the results the site gains 100% performance benefits but every once in a while annoys a customer because the fare has expired. But the trade off works in the favour of these sites as they are still able to process up to 30+ page requests per second which means cater to the site traffic by may be losing 1 customer every once in a while to a competitor who is also using a similar caching technique what are the odds that the user will not come back to their site sooner or later? Recap   Resources Below are some Key resource you might like to review. I would highly recommend the documentation, walkthroughs and videos available on MSDN. You can always make use of Fiddler to debug Web Performance Tests. Some community test extensions and plug ins available on Codeplex might also be of interest to you. The Road Ahead Thank you for taking the time out and reading this blog post, you may also want to read Part I and Part II if you haven’t so far. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Questions/Feedback/Suggestions, etc please leave a comment. Next ‘Load Testing in the cloud’, I’ll be working on exploring the possibilities of running Test controller/Agents in the Cloud. See you on the other side! Thank You!   Share this post : CodeProject

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  • Chaning coding style due to Android GC performance, how far is too far?

    - by Benju
    I keep hearing that Android applications should try to limit the number of objects created in order to reduce the workload on the garbage collector. It makes sense that you may not want to created massive numbers of objects to track on a limited memory footprint, for example on a traditional server application created 100,000 objects within a few seconds would not be unheard of. The problem is how far should I take this? I've seen tons of examples of Android applications relying on static state in order supposedly "speed things up". Does increasing the number of instances that need to be garbage collected from dozens to hundreds really make that big of a difference? I can imagine changing my coding style to now created hundreds of thousands of objects like you might have on a full-blown Java-EE server but relying on a bunch of static state to (supposedly) reduce the number of objects to be garbage collected seems odd. How much is it really necessary to change your coding style in order to create performance Android apps?

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  • Weak reference and Strong reference

    - by theband
    package uk.co.bigroom.utils { import flash.utils.Dictionary; /** * Class to create a weak reference to an object. A weak reference * is a reference that does not prevent the object from being * garbage collected. If the object has been garbage collected * then the get method will return null. */ public class WeakRef { private var dic:Dictionary; /** * The constructor - creates a weak reference. * * @param obj the object to create a weak reference to */ public function WeakRef( obj:* ) { dic = new Dictionary( true ); dic[obj] = 1; } /** * To get a strong reference to the object. * * @return a strong reference to the object or null if the * object has been garbage collected */ public function get():* { for ( var item:* in dic ) { return item; } return null; } } } In this Class, how they denote one as Weak Reference and one as Strong reference.

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  • Pointers, links, object and reference count

    - by EugeneP
    String a = "a"; // allocate memory and write address of a memory block to a variable String b = "b"; // in a and b hold addresses b = a; // copy a address into b. // Now what? b value is completely lost and will be garbage collected //* next step a = null; // now a does not hold a valid address to any data, // still data of a object exist somewhere, yet we cannot get access to it. Correct me if there's a mistake somewhere in my reflexions. My question is: suppose anInstance object of type Instance has a property ' surname ' anInstance.getSurname() returns "MySurname". now String s = anInstance.getSurname(); anInstance = null; question is - is it true that getSurname value, namely MySurname will not be garbage collected because and only because it has active reference counter 0, and if other properties of anInstance have a zero reference counter, they'll be garbage collected?

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  • Python - Memory Leak

    - by Dave
    I'm working on solving a memory leak in my Python application. Here's the thing - it really only appears to happen on Windows Server 2008 (not R2) but not earlier versions of Windows, and it also doesn't look like it's happening on Linux (although I haven't done nearly as much testing on Linux). To troubleshoot it, I set up debugging on the garbage collector: gc.set_debug(gc.DEBUG_UNCOLLECTABLE | gc.DEBUG_INSTANCES | gc.DEBUG_OBJECTS) Then, periodically, I log the contents of gc.garbage. Thing is, gc.garbage is always empty, yet my memory usage goes up and up and up. Very puzzling.

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  • Lucene and Special Characters

    - by Brandon
    I am using Lucene.Net 2.0 to index some fields from a database table. One of the fields is a 'Name' field which allows special characters. When I perform a search, it does not find my document that contains a term with special characters. I index my field as such: Directory DALDirectory = FSDirectory.GetDirectory(@"C:\Indexes\Name", false); Analyzer analyzer = new StandardAnalyzer(); IndexWriter indexWriter = new IndexWriter(DALDirectory, analyzer, true, IndexWriter.MaxFieldLength.UNLIMITED); Document doc = new Document(); doc.Add(new Field("Name", "Test (Test)", Field.Store.YES, Field.Index.TOKENIZED)); indexWriter.AddDocument(doc); indexWriter.Optimize(); indexWriter.Close(); And I search doing the following: value = value.Trim().ToLower(); value = QueryParser.Escape(value); Query searchQuery = new TermQuery(new Term(field, value)); Searcher searcher = new IndexSearcher(DALDirectory); TopDocCollector collector = new TopDocCollector(searcher.MaxDoc()); searcher.Search(searchQuery, collector); ScoreDoc[] hits = collector.TopDocs().scoreDocs; If I perform a search for field as 'Name' and value as 'Test', it finds the document. If I perform the same search as 'Name' and value as 'Test (Test)', then it does not find the document. Even more strange, if I remove the QueryParser.Escape line do a search for a GUID (which, of course, contains hyphens) it finds documents where the GUID value matches, but performing the same search with the value as 'Test (Test)' still yields no results. I am unsure what I am doing wrong. I am using the QueryParser.Escape method to escape the special characters and am storing the field and searching by the Lucene.Net's examples. Any thoughts?

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  • Apache Lucene: Is Relevance Score Always Between 0 and 1?

    - by Eamorr
    Greetings, I have the following Apache Lucene snippet that's giving me some nice results: int numHits=100; int resultsPerPage=100; IndexSearcher searcher=new IndexSearcher(reader); TopScoreDocCollector collector=TopScoreDocCollector.create(numHits,true); Query q=parser.parse(queryString); searcher.search(q,collector); ScoreDoc[] hits=collector.topDocs(0*resultsPerPage,resultsPerPage).scoreDocs; Results r=new Results(); r.length=hits.length; for(int i=0;i<hits.length;i++){ Document doc=searcher.doc(hits[i].doc); double distanceKm=getGreatCircleDistance(lucene2double(doc.get("lat")), lucene2double(doc.get("lng")), Double.parseDouble(userLat), Double.parseDouble(userLng)); double newRelevance=((1/distanceKm)*Math.log(hits[i].score)/Math.log(2))*(0-1); System.out.println(hits[i].doc+"\t"+hits[i].score+"\t"+doc.get("content")+"\t"+"Km="+distanceKm+"\trlvnc="+String.valueOf(newRelevance)); } What I want to know, is hits[i].score always between 0 and 1? It seems that way, but I can't be sure. I've even checked the Lucene documentation (class ScoreDocs) to no avail. You'll see I'm calculating the log of the "newRelevance" value, which is based on hits[i].score. I need hits[i].score to be between 0 and 1, because if it is below zero, I'll get an error; above 1 and the sign will change from negative to positive. I hope some Lucene expert out there can offer me some insight. Many thanks,

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  • Azure Blob storage defrag

    - by kaleidoscope
    The Blob Storage is really handy for storing temporary data structures during a scaled-out distributed processing. Yet, the lifespan of those data structures should not exceed the one of the underlying operation, otherwise clutter and dead data could potentially start filling up your Blob Storage Temporary data in cloud computing is very similar to memory collection in object oriented languages, when it's not done automatically by the framework, temp data tends to leak. In particular, in cloud computing,  it's pretty easy to end up with storage leaks due to: Collection omission. App crash. Service interruption. All those events cause garbage to accumulate into your Blob Storage. Then, it must be noted that for most cloud apps, I/O costs are usually predominant compared to pure storage costs. Enumerating through your whole Blob Storage to clean the garbage is likely to be an expensive solution. Lokesh, M

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  • Which Programming Languages Support the Following Features?

    - by donalbain
    My personal programming background is mainly in Java, with a little bit of Ruby, a tiny bit of Scheme, and most recently, due to some iOS development, Objective-C. In my move from Java to Objective-C I've really come to love some features that Objective-C has that Java doesn't. These include support for both static and dynamic typing, functional programming, and closures, which I'm trying to leverage in my code more often. Unfortunately there are trade-offs, including lack of support for generics and (on iOS at least) no garbage collection. These contrasts have lead me to start a search for some of the programming languages that support the following features: Object Oriented Functional Programming Support Closures Generics Support for both Static and Dynamic Typing Module Management to avoid classpath/dll hell Garbage Collection Available Decent IDE Support Admittedly some of these features(IDE support, Module Management) may not be specific to the language itself, but obviously influence the ease of development in the language. Which languages fit these criteria?

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  • Why is Java the lingua franca at so many institutions?

    - by Billy ONeal
    EDIT: This question at first seems to be bashing Java, and I guess at this point it is a bit. However, the bigger point I am trying to make is why any one single language is chosen as the one end all be all solution to all problems. Java happens to be the one that's used so that's the one I had to beat on here, but I'm not intentionality ripping Java a new one :) I don't like Java in most academic settings. I'm not saying the language itself is bad -- it has several extremely desirable aspects, most importantly the ability to run without recompilation on most any platform. Nothing wrong with using the language for Your Next App ^TM. (Not something I would personally do, but that's more because I have less experience with it, rather than it's design being poor) I think it is a waste that high level CS courses are taught using Java as a language. Too many of my co-students cannot program worth a damn, because they don't know how to work in a non-garbage-collected world. They don't fundamentally understand the machines they are programming for. When someone can work outside of a garbage collected world, they can work inside of one, but not vice versa. GC is a tool, not a crutch. But the way it is used to teach computer science students is a as a crutch. Computer science should not teach an entire suite of courses tailored to a single language. Students leave with the idea that all good design is idiomatic Java design, and that Object Oriented Design is the ONE TRUE WAY THAT IS THE ONLY WAY THINGS CAN BE DONE. Other languages, at least one of them not being a garbage collected language, should be used in teaching, in order to give the graduate a better understanding of the machines. It is an embarrassment that somebody with a PHD in CS from a respected institution cannot program their way out of a paper bag. What's worse, is that when I talk to those CS professors who actually do understand how things operate, they share feelings like this, that we're doing a disservice to our students by doing everything in Java. (Note that the above would be the same if I replaced it with any other language, generally using a single language is the problem, not Java itself) In total, I feel I can no longer respect any kind of degree at all -- when I can't see those around me able to program their way out of fizzbuzz problems. Why/how did it get to be this way?

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  • Why can't Java/C# implement RAII?

    - by mike30
    Question: Why can't Java/C# implement RAII? Clarification: I am aware the garbage collector is not deterministic. So with the current language features it is not possible for an object's Dispose() method to be called automatically on scope exit. But could such a deterministic feature be added? My understanding: I feel an implementation of RAII must satisfy two requirements: 1. The lifetime of a resource must be bound to a scope. 2. Implicit. The freeing of the resource must happen without an explicit statement by the programmer. Analogous to a garbage collector freeing memory without an explicit statement. The "implicitness" only needs to occur at point of use of the class. The class library creator must of course explicitly implement a destructor or Dispose() method. Java/C# satisfy point 1. In C# a resource implementing IDisposable can be bound to a "using" scope: void test() { using(Resource r = new Resource()) { r.foo(); }//resource released on scope exit } This does not satisfy point 2. The programmer must explicitly tie the object to a special "using" scope. Programmers can (and do) forget to explicitly tie the resource to a scope, creating a leak. In fact the "using" blocks are converted to try-finally-dispose() code by the compiler. It has the same explicit nature of the try-finally-dispose() pattern. Without an implicit release, the hook to a scope is syntactic sugar. void test() { //Programmer forgot (or was not aware of the need) to explicitly //bind Resource to a scope. Resource r = new Resource(); r.foo(); }//resource leaked!!! I think it is worth creating a language feature in Java/C# allowing special objects that are hooked to the stack via a smart-pointer. The feature would allow you to flag a class as scope-bound, so that it always is created with a hook to the stack. There could be a options for different for different types of smart pointers. class Resource - ScopeBound { /* class details */ void Dispose() { //free resource } } void test() { //class Resource was flagged as ScopeBound so the tie to the stack is implicit. Resource r = new Resource(); //r is a smart-pointer r.foo(); }//resource released on scope exit. I think implicitness is "worth it". Just as the implicitness of garbage collection is "worth it". Explicit using blocks are refreshing on the eyes, but offer no semantic advantage over try-finally-dispose(). Is it impractical to implement such a feature into the Java/C# languages? Could it be introduced without breaking old code?

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  • Is it safe to run multiple XNA ContentManager instances on multiple threads?

    - by Boinst
    My XNA project currently uses one ContentManager instance, and one dedicated background thread for loading all content. I wonder, would it be safe to have multiple ContentManager instances, each in it's own dedicated thread, loading different content at the same time? I'm prompted to ask this question because this article makes the following statement: If there are two textures created at the same time on different threads, they will clobber the other and you will end up with some garbage in the textures. I think that what the author is saying here, is that if I access one ContentManager simultaneously on two threads, I'll get garbage. But what if I have separate ContentManager instances for each thread? If no-one knows the answer already from experience, I'll go ahead and try it and see what happens.

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  • which performance counters mainly matter for windows server performance?

    - by Karl Cassar
    We have a website which is sometimes performing slowly, and / or completely hangs. I have setted up temporarily the default system performance data collector in Performance Monitor, to see if this can shed some light. However, the default Data Collector set collects a huge amount of counters, as well as generates huge logs files. Just 8 hours of data resulted in 4GB of data. Which performance counters matter the most, when judging server load? Also, is it a performance concern if one leaves such data-collectors running indefinitely? Obviously, I will not know when the server will experience slow performance, so I need the logs there so that I can check them out. Any other specific guidelines on monitoring server performance would be greatly appreciated. OS is a Windows Server 2008 R2 (Web Edition).

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  • SQL SERVER – Configure Management Data Collection in Quick Steps – T-SQL Tuesday #005

    - by pinaldave
    This article was written as a response to T-SQL Tuesday #005 – Reporting. The three most important components of any computer and server are the CPU, Memory, and Hard disk specification. This post talks about  how to get more details about these three most important components using the Management Data Collection. Management Data Collection generates the reports for the three said components by default. Configuring Data Collection is a very easy task and can be done very quickly. Please note: There are many different ways to get reports generated for CPU, Memory and IO. You can use DMVs, Extended Events as well Perfmon to trace the data. Keeping the T-SQL Tuesday subject of reporting this post is created to give visual tutorial to quickly configure Data Collection and generate Reports. From Book On-Line: The data collector is a core component of the Data Collection platform for SQL Server 2008 and the tools that are provided by SQL Server. The data collector provides one central point for data collection across your database servers and applications. This collection point can obtain data from a variety of sources and is not limited to performance data, unlike SQL Trace. Let us go over the visual tutorial on how quickly Data Collection can be configured. Expand the management node under the main server node and follow the direction in the pictures. This reports can be exported to PDF as well Excel by writing clicking on reports. Now let us see more additional screenshots of the reports. The reports are very self-explanatory  but can be drilled down to get further details. Click on the image to make it larger. Well, as we can see, it is very easy to configure and utilize this tool. Do you use this tool in your organization? Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL Reporting, SQL Reports

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