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  • [NEWVERSION]algorithm || method to write prog[UNSOLVED] [closed]

    - by fatai
    I am one of the computer science student. Everyone solve problem with a different or same method, ( but actually I dont know whether they use method or I dont know whether there are such common method to approach problem.) if there are common method, What is it ? If there are different method, which method are you using ? All teacher give us problem which in simple form sometimes, but they donot introduce any approach or method(s) so that we cannot make a decision to choose the method then apply that one to problem , afterward find solution then write code.No help from teacher , push us to find method to solve homework. Ex: my friend is using no method , he says "I start to construct algorithm while I try to write prog." I have found one method when I failed the course, More accurately, my method: When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 now, my other question is ; What is/are other method(s) which have/has been; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c by other user? Some programmer uses generalized method without considering prog-language(java , perl .. ), what is this method ? Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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  • .NET JIT Code Cache leaking?

    - by pitchfork
    We have a server component written in .Net 3.5. It runs as service on a Windows Server 2008 Standard Edition. It works great but after some time (days) we notice massive slowdowns and an increased working set. We expected some kind of memory leak and used WinDBG/SOS to analyze dumps of the process. Unfortunately the GC Heap doesn’t show any leak but we noticed that the JIT code heap has grown from 8MB after the start to more than 1GB after a few days. We don’t use any dynamic code generation techniques by our own. We use Linq2SQL which is known for dynamic code generation but we don’t know if it can cause such a problem. The main question is if there is any technique to analyze the dump and check where all this Host Code Heap blocks that are shown in the WinDBG dumps come from? [Update] In the mean time we did some more analysis and had Linq2SQL as probable suspect, especially since we do not use precompiled queries. The following example program creates exactly the same behaviour where more and more Host Code Heap blocks are created over time. using System; using System.Linq; using System.Threading; namespace LinqStressTest { class Program { static void Main(string[] args) { for (int i = 0; i < 100; ++ i) ThreadPool.QueueUserWorkItem(Worker); while(runs < 1000000) { Thread.Sleep(5000); } } static void Worker(object state) { for (int i = 0; i < 50; ++i) { using (var ctx = new DataClasses1DataContext()) { long id = rnd.Next(); var x = ctx.AccountNucleusInfos.Where(an => an.Account.SimPlayers.First().Id == id).SingleOrDefault(); } } var localruns = Interlocked.Add(ref runs, 1); System.Console.WriteLine("Action: " + localruns); ThreadPool.QueueUserWorkItem(Worker); } static Random rnd = new Random(); static long runs = 0; } } When we replace the Linq query with a precompiled one, the problem seems to disappear.

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  • jqtransform and collapsed DIV

    - by Marco
    Hello, I am using a jQuery plugin called: jqtransform This plugin uses JavaScript to apply CSS styles to form elements. The problem that I have consists in the following scenario: I’m building a search page, with a advanced search option. When the page loads, the div called “advancedSearch” is hidden, and it will only show if the user clicks a element. Inside the div#advancedSearch I have several form elements. However, if I hide the div#advancedSearch with the CSS style: “diplay:none;”, the jqtransform plugin doesn’t work correctly with the elements that are hidden. So my solution was to hide the div#advancedsearch with JavaScript. This actually works, and it does not matter if it’s done after the document is ready or not. But… with the JavaScript solution, the div#advancedSearch stays visible for a couple of milliseconds… which is visually annoying. So I was wondering if the solution to this problem would be in the CSS, or in correcting the jqtransform plugin, or even in finding a way to immediately hide the div#advancedSearch with JS making it immediately hidden. UPDATE 1 After jeerose comment I decided to place here my function (please note that the <%= % are ASP.Net tags, that I use to get the images path) $('.toggleAdvancedSearch').click(function() { $('#advancedSearchWrap').slideToggle(250); $('form.jqtransform').jqTransform({ imgPath: '<%= ResolveClientUrl("~/masterpages/img/jqtransform/") %>' }); return false; }); UPDATE 2 To test the problem, I did the following: Added another element to the page, with the ID “applyStyle”, and onClick I call the $('form').jqTransform(); Disabled the the $('form').jqTransform(); from the load of the page. If I press the a#applyStyle, before expanding the div#advancedSearch I get the same problem that I had. But if I expand the the div#advancedSearch and press the the a#applyStyle after, the problem is solved. However, if I run the page with the $('form').jqTransform(); function on the load, I cannot reapply it after with the pressing of the a#applyStyle. I think that the solution could be: disabling the all the elements that are inside the div#advancedSearch, and on the same function that expands the div, make It also apply the styles to the elements that are inside the div#advancedSearch. However, I don’t know how to do this (nether if this will work). PS: This seems to be a known issue with the plugin, but I cannot wait indefinitely for a solution.

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  • Available Coroutine Libraries in Java

    - by JUST MY correct OPINION
    I would like to do some stuff in Java that would be clearer if written using concurrent routines, but for which full-on threads are serious overkill. The answer, of course, is the use of coroutines, but there doesn't appear to be any coroutine support in the standard Java libraries and a quick Google on it brings up tantalising hints here or there, but nothing substantial. Here's what I've found so far: JSIM has a coroutine class, but it looks pretty heavyweight and conflates, seemingly, with threads at points. The point of this is to reduce the complexity of full-on threading, not to add to it. Further I'm not sure that the class can be extracted from the library and used independently. Xalan has a coroutine set class that does coroutine-like stuff, but again it's dubious if this can be meaningfully extracted from the overall library. It also looks like it's implemented as a tightly-controlled form of thread pool, not as actual coroutines. There's a Google Code project which looks like what I'm after, but if anything it looks more heavyweight than using threads would be. I'm basically nervous of something that requires software to dynamically change the JVM bytecode at runtime to do its work. This looks like overkill and like something that will cause more problems than coroutines would solve. Further it looks like it doesn't implement the whole coroutine concept. By my glance-over it gives a yield feature that just returns to the invoker. Proper coroutines allow yields to transfer control to any known coroutine directly. Basically this library, heavyweight and scary as it is, only gives you support for iterators, not fully-general coroutines. The promisingly-named Coroutine for Java fails because it's a platform-specific (obviously using JNI) solution. And that's about all I've found. I know about the native JVM support for coroutines in the Da Vinci Machine and I also know about the JNI continuations trick for doing this. These are not really good solutions for me, however, as I would not necessarily have control over which VM or platform my code would run on. (Indeed any bytecode manipulation system would suffer similar problems -- it would be best were this pure Java if possible. Runtime bytecode manipulation would restrict me from using this on Android, for example.) So does anybody have any pointers? Is this even possible? If not, will it be possible in Java 7? Edited to add: Just to ensure that confusion is contained, this is a related question to my other one, but not the same. This one is looking for an existing implementation in a bid to avoid reinventing the wheel unnecessarily. The other one is a question relating to how one would go about implementing coroutines in Java should this question prove unanswerable. The intent is to keep different questions on different threads.

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  • Which MarkDown (WMD) javascript editor should I use?

    - by Edan Maor
    Background I'm working on an application which requires user-entered content, and I've decided to use a StackOverflow-style MarkDown editor. After researching this topic for the last few days, I realize there are numerous forks of the base WMD editor, some with a few basic enhancements and some with serious differences from the StackOverflow one. Since this will be the heart of the application, I'd like to start with the best code base I can. I'd be happy if anyone can recommend which one of the many solutions out there best fits my needs. Below is requirements, plus what I've managed to find already. I'm hoping this question will help me decide which version to go with, and maybe help me discover a port out there that's an even better fit for my needs. The requirements for my project Live Preview Multiple editors on the same page (not know how many in advance, since the user can dynamically add another editing box). Ability to extend with extra buttons (I'd like a button to upload a picture, instead of just adding an img url). Ability to dynamically show/hide the edit box (and only see the preview box). Not an absolute must, but I'd prefer to stick as close to StackOverflow's look and feel, since it's well known. Don't know if this matters, but the backend is written in Django. Editors I've looked at Here are a few of the code bases I've looked at, with thoughts. Obviously, I might be missing another solution out there. The derobins version. From what I can tell, this is the official StackOverflow version. Seems like it doesn't support multiple editors on one page. JQuery.MarkEdit. Looks very good, but is pretty different from the StackOverflow version. MooWMD. Looks like the winner right now, but I'm a little concerned since it looks less active/hackable than MarkEdit. The wmd-new version. Not sure, looks like an old codebase without much use. The SocialSite branch. Seems like it's not for public use.

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  • JAX-WS wsgen and collections of collections: wsgen broken?

    - by ayang
    I've been playing around with "bottom-up" JAX-WS and have come across something odd when running wsgen. If I have a service class that does something like: @WebService public class Foo { public ArrayList<Bar> getBarList(String baz) { ... } } then running wsgen gets me a FooService_schema1.xsd that has something like this: <xs:complexType name="getBarListResponse"> <xs:sequence> <xs:element name="return" type="tns:bar" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> which seems reasonable. However, if I want a collection of collections like: public BarCollection getBarCollection(String baz) { ... } // BarCollection is just a container for an ArrayList<Bar> then the generated schema ends up with stuff like: <xs:complexType name="barCollection"> <xs:sequence/> </xs:complexType> <xs:complexType name="getBookCollectionsResponse"> <xs:sequence> <xs:element name="return" type="tns:barCollection" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> An empty sequence is not what I had in mind at all. My original approach was to go with: public ArrayList<ArrayList<Bar>> getBarLists(String baz) { ... } but that ends up with a big chain of complexTypes that just wind up with an empty sequence at the end as well: <xs:complexType name="getBarListsResponse"> <xs:sequence> <xs:element name="return" type="tns:arrayList" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> <xs:complexType name="arrayList"> <xs:complexContent> <xs:extension base="tns:abstractList"> <xs:sequence/> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="abstractList" abstract="true"> <xs:complexContent> <xs:extension base="tns:abstractCollection"> <xs:sequence/> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="abstractCollection" abstract="true"> <xs:sequence/> </xs:complexType> Am I missing something or is this a known hole in wsgen? JAXB? Andy

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  • Another C datatypes question

    - by b-gen-jack-o-neill
    Hello. Well, I completely get the most basic datatypes of C, like short, int, long, float, to be exact, all numerical types.These types are needed to be known perform right operations with right numbers. For example to use FPU to add two float numbers. So the compiler must know what the type is. But, when it comes to characters I am little bit off. I know that basic C datatype char is there for ASCII characters coding. But what I don´t know is, why you even need another datatype for characters. Why could not you just use 1 byte integer value to store ASCII character. If you call printf, you apecify the datatype in the call, so you could say to printf that the integer represents ASCII character. I dont know how cout resolves datatype, but I guess you could just specify it somehow. Another thing is, when you want to use Unicode, you must use datatype wchar. But, what if I would like to use some another, for example ISO, or Windows coding instead of UTF? Becouse wchar codes characters as UTF-16 or UTF-32 (I read its compiler specific). And, what if I would want to use for example some imaginary new 8 byte text coding? What datatype should I use for it? I am actually pretty confused of this, becouse I always expected that if I want to use UTF-32 instead of ASCII, I just tell compiler "get UTF-32 value of the character I typed and save it into 4 char field." I thought that text coding is to be dealt with by the end, print function for example. That I just need to specify the coding for the compiler to use, since Windows doesent use ASCII in win32 apps, I guess C compiler must convert the char I typed to ASCII from whatever the type is that windows sends to the C editor. And the last thing is, what if I want to use for example 25 Byte integer for some high math operations? C has no specify-yourself datatype. Yes, I know that this would be difficult since all the math operations would need to be changed, becouse CPU can not add 25 Bytes numbers together. But is there a way to do it? Or is there some math library for it? What if I want to compute Pi to 1000000000000000 digits? :) I know my question is pretty long, but I just wanted to explain my thoughts the best I can in English, since its not my native language it is difficult. And I believe there is simple answer to my question(s), something I missed that explains everything. I read lot about text coding, C tutorials, but nothing about his. Thank you for your time.

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  • php array code with regular expressions

    - by user551068
    there are few mistakes which it is showing as Warning: preg_match() [function.preg-match]: Delimiter must not be alphanumeric or backslash in array 4,9,10,11,12... can anyone resolve them <?PHP $hosts = array( array("ronmexico.kainalopallo.com/","beforename=$F_firstname%20$F_lastname&gender=$F_gender","Your Ron Mexico Name is ","/the ultimate disguise, is <u><b>([^<]+)<\/b><\/u>/s"), array("www.fjordstone.com/cgi-bin/png.pl","gender=$F_gender&submit=Name%20Me","Your Pagan name is ","/COLOR=#000000 SIZE=6> *([^<]*)<\/FONT>/"), array("rumandmonkey.com/widgets/toys/mormon/index.php","gender=$F_gender&firstname=$F_firstname&surname=$F_lastname","Your Mormon Name is ","/<p>My Mormon name is <b>([^<]+)<\/b>!<br \/>/s"), array("cyborg.namedecoder.com/index.php","acronym=$F_firstname&design=edox&design_click-edox.x=0&design_click-edox.y=0&design_click-edox=edo","","Your Cyborg Name is ","/<p>([^<]+)<\/p>/"), array("rumandmonkey.com/widgets/toys/namegen/10/","nametype=$brit&page=2&id=10&submit=God%20save%20the%20Queen!&name=$F_firstname%20$F_lastname","Your Very British Name is ","/My very British name is \&lt\;b\&gt;([^&]+)\&lt;\/b\&gt;\.\&lt;br/"), array("blazonry.com/name_generator/usname.php","realname=$F_firstname+$F_lastname&gender=$F_gender","Your U.S. Name is ","/also be known as <font size=\'\+1\'><b>([^<]+)<\/b>/s"), array("www.spacepirate.org/rogues.php","realname=$F_firstname%20$F_lastname&formentered=Yes&submit=Arrrgh","Your Space Pirate name is ","/Your pirate name is <font size=\'\+1\'><b>([^<]+)<\/b><\/font>/s"), array("rumandmonkey.com/widgets/toys/ghetto/","firstname=$F_firstname&lastname=$F_lastname","Your Ghetto Name is ","/<p align=\"center\" style=\"font-size: 36px\">\s*<br \/>\s*([^<]*)<br \/>/"), array("www.emmadavies.net/vampire/default.aspx","mf=$emgender&firstname=$F_firstname&lastname=$F_lastname&submit=Find+My+Vampire+Name","","Your Vampire Name is ","/<i class=\"vampirecontrol vampire name\">([^<]*)<\/i>/"), array("www.emmadavies.net/fairy/default.aspx","mf=$emgender&firstname=$F_firstname&lastname=$F_lastname&submit=Seek+Fairy","","Your Fairy Name is ","/<i class=\'ng fairy name\'>([^<]*)<\/i>/"), array("www.irielion.com/israel/reggaename.html","phase=3&oldname=$F_firstname%20$F_lastname&gndr=$reggender","","Your Rasta Name is ","/Yes I, your irie new name is ([^\n]*)\n/"), array("www.ninjaburger.com/fun/games/ninjaname/ninjaname.php","realname=$F_firstname+$F_lastname","Your Ninja Burger Name is ","/<BR>Ninja Burger ninja name will be<BR><BR><FONT SIZE=\'\+1\'>([^<]*)<\/FONT>/"), array("gangstaname.com/pirate_name.php","sex=$F_gender&name=$F_firstname+$F_lastname","Your Pirate Name is ","/<p><strong>We\'ll now call ye:<\/strong><\/p> *<h2 class=\"newName\">([^<]*)<\/h2>/"), array("www.xach.com/nerd-name/","name=$F_firstname+$F_lastname&gender=$F_gender","Your Nerd Name is ","/<p><div align=center class=\"nerdname\">([^<]*)<\/div>/"), array("rumandmonkey.com/widgets/toys/namegen/5941/","page=2&id=5941&nametype=$dj&name=$F_firstname+$F_lastname","Your DJ Name is ","/My disk spinnin nu name is &lt\;b&gt\;([^<]*)&lt\;\/b&gt\;\./"), array("pizza.sandwich.net/poke/pokecgi.cgi","name=$F_firstname%20$F_lastname&color=black&submit=%20send%20","Your Pokename is ","/Your Pok&eacute;name is: <h1>([^<]*)<\/h1>/") ); return $hosts; ?>

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  • how to implement a "soft barrier" in multithreaded c++

    - by Jason
    I have some multithreaded c++ code with the following structure: do_thread_specific_work(); update_shared_variables(); //checkpoint A do_thread_specific_work_not_modifying_shared_variables(); //checkpoint B do_thread_specific_work_requiring_all_threads_have_updated_shared_variables(); What follows checkpoint B is work that could have started if all threads have reached only checkpoint A, hence my notion of a "soft barrier". Typically multithreading libraries only provide "hard barriers" in which all threads must reach some point before any can continue. Obviously a hard barrier could be used at checkpoint B. Using a soft barrier can lead to better execution time, especially since the work between checkpoints A and B may not be load-balanced between the threads (i.e. 1 slow thread who has reached checkpoint A but not B could be causing all the others to wait at the barrier just before checkpoint B). I've tried using atomics to synchronize things and I know with 100% certainty that is it NOT guaranteed to work. For example using openmp syntax, before the parallel section start with: shared_thread_counter = num_threads; //known at compile time #pragma omp flush Then at checkpoint A: #pragma omp atomic shared_thread_counter--; Then at checkpoint B (using polling): #pragma omp flush while (shared_thread_counter > 0) { usleep(1); //can be removed, but better to limit memory bandwidth #pragma omp flush } I've designed some experiments in which I use an atomic to indicate that some operation before it is finished. The experiment would work with 2 threads most of the time but consistently fail when I have lots of threads (like 20 or 30). I suspect this is because of the caching structure of modern CPUs. Even if one thread updates some other value before doing the atomic decrement, it is not guaranteed to be read by another thread in that order. Consider the case when the other value is a cache miss and the atomic decrement is a cache hit. So back to my question, how to CORRECTLY implement this "soft barrier"? Is there any built-in feature that guarantees such functionality? I'd prefer openmp but I'm familiar with most of the other common multithreading libraries. As a workaround right now, I'm using a hard barrier at checkpoint B and I've restructured my code to make the work between checkpoint A and B automatically load-balancing between the threads (which has been rather difficult at times). Thanks for any advice/insight :)

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  • Assembly Load and loading the "sub-modules" dependencies - "cannot find the file specified"

    - by Ted
    There are several questions out there that ask the same question. However the answers they received I cannot understand, so here goes: Similar questions: http://stackoverflow.com/questions/1874277/dynamically-load-assembly-and-manually-force-path-to-get-referenced-assemblies ; http://stackoverflow.com/questions/22012/loading-assemblies-and-its-dependencies-closed The question in short: I need to figure out how dependencies, ie References in my modules can be loaded dynamically. Right now I am getting "The system cannot find the file specified" on Assemblies referenced in my so called modules. I cannot really get how to use the AssemblyResolve event... The longer version I have one application, MODULECONTROLLER, that loads separate modules. These "separate modules" are located in well-known subdirectories, like appBinDir\Modules\Module1 appBinDir\Modules\Module2 Each directory contains all the DLLs that exists in the bin-directory of those projects after a build. So the MODULECONTROLLER loads all the DLLs contained in those folders using this code: byte[] bytes = File.ReadAllBytes(dllFileFullPath); Assembly assembly = null; assembly = Assembly.Load(bytes); I am, as you can see, loading the byte[]-array (so I dont lock the DLL-files). Now, in for example MODULE1, I have a static reference called MyGreatXmlProtocol. The MyGreatXmlProtocol.dll then also exists in the directory appBinDir\Modules\Module1 and is loaded using the above code When code in the MODULE1 tries to use this MyGreatXmlProtocol, I get: Could not load file or assembly 'MyGreatXmlProtocol, Version=1.0.3797.26527, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified. So, in a post (like this one) they say that To my understanding reflection will load the main assembly and then search the GAC for the referenced assemblies, if it cannot find it there, you can then incorparate an assemblyResolve event: First; is it really needed to use the AssemblyResolve-event to make this work? Shouldnt my different MODULEs themself load their DLLs, as they are statically referenced? Second; if AssemblyResolve is the way to go - how do I use it? I have attached a handler to the Event but I never get anything on MyGreatXmlProctol... === EDIT === CODE regarding the AssemblyResolve-event handler: public GUI() { InitializeComponent(); AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(CurrentDomain_AssemblyResolve); ... } // Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args) { Console.WriteLine(args.Name); return null; } Hope I wasnt too fuzzy =) Thx

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  • javascript simple object creation test: opera leaks?

    - by joe
    Hi, I am trying to figure out certain memory leak conditions in javascript on a few browsers. Currently I'm only testing FF 3.6, Opera 10.10, and Safari 4.0.3. I've started with a fairly simple test, and can confirm no memory leaks in Firefox and Safari. But Opera just takes memory and never gives it back. What gives? Here's the test: <html> <head> <script type="text/javascript"> window.onload = init; //window.onunload = cleanup; var a=[]; function init() { var d = document.createElement('div'); d.innerHTML = "page loading..."; document.body.appendChild(d); for (var i=0; i<400000; i++) { a[i] = new Obj("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"); } d.innerHTML = "PAGE LOADED"; } function cleanup() { for (var i=0; i<400000; i++) { a[i] = null; } } function Obj(msg) { this.msg=msg; } </script> </head> <body> </body> </html> I shouldn't need the cleanup() call on window.unload, but tried that also. No luck. As you can see this is simple JS, no circular DOM links, no closures. I monitor the memory usage using 'top' on Mac 10.4.11. Memory usage spikes up on page load, as expected. In FF and Safari reloading the page does not use any further memory, and all memory is returned when the window (tab) is closed. In Opera, memory spikes on load, and seems to also spike further on each reload (but not always...). But regardless of reload, memory never goes back down below the initial load spike. I had hoped this was a no-brainer test that all browsers would pass, so I could move on to more "interesting" conditions. Am I doing something wrong here? Or is this a known Opera issue? Thanks! -joe

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  • Creating a music catalog and extracting first 30 seconds as soon as the first words are sung

    - by Rad
    I already read a question: Separation of singing voice from music. I don’t need this complex audio processing. I only need some detection mechanism that would detect that there is some voice/vocal playing while the music is playing (or not playing) I need to extract first 30 seconds when a vocalist starts singing along with full band music. See question 2 below. I want to create a music catalog using ASP.NET MVC 2 and Silverlight clients and C#.NET 4.0 programming language that would be front store. On the backend I would also like to create a desktop WPF/Windows application to create the music catalog from already existing music files, most of which have metadata in them ID3v1, ID3v2.3, ID3v2.4, iTunes MP4, WMA, Vorbis Comments and APE Tags etc. I would possibly like to create a web service that would allow catalog contributors to upload a zipped album and trigger metadata extraction of music data and extraction of music segments as described below. I would be happy if I achieve no. 1 below. Let's say I have 1000ths of songs in mp3 (or other formats) grouped in subfolders using some classification (Genre, Artists, Albums, Composers or other groupings). I want to create tables in DB that would organize songs so they can be searched based on different criteria (year, length, above classification or by song title, description etc) like what iTune store allows to their customers. I want to extract metadata from various formats (I will try to get songs in mp3 format, but there may be other popular formats) and allow music Catalog manager person to add missing data from either desktop or web applications. He or other contributors can upload zipped music via an HTML or Silverlight upload or WPF. Can anybody suggest open source libraries, articles, code snippets that can do that in an automatic way using .NET and possibly SQL Server DB? My main questions are these. This is an audio processing challenge. I want to extract 2 segments of music (questions 1 and 2): 1. How to extract a music segment: 1-2 seconds before a vocal starts singing and up to 30 seconds from that point in time and 2. Much more challenging is to find repeating segments (One would usually find or recognize the names of the songs and songs are usually known by these refrains. How would I go about creating a list of songs that go great together like what Genius from iTune does? Is there any characteristics of music that can be used to match songs? The goal is for people quickly scan and recognize songs i.e. associate melody, words with a title/album so they can make intelligent decisions like buying a song, create similar mood songs.

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  • Collision point of 2 curves in a 3d-room

    - by Frank
    Hello, i am programming a small game for quite some time. We started coding a small FPS-Shooter inside of a project at school to get a bit experience using directX. I dont know why, but i couldnt stop the project and started programming at home aswell. At the moment i am trying to create some small AI. Of cause thats definatlly not easy, but thats my personal goal anyways. The topic could prolly fill multiple books hehe. I've got the walking part of my bots done so far. They walk along a scriped path. I am not working on the "aiming" of the bots. While programming that i hit on some math problem i couldnt solve yet. I hope of your input on this to help me get further. Concepts, ideas and everything else are highly appreciated. Problem: Calculate the position (D3DXVECTOR3) where the curve of the projectile (depends on gravity, speed), hit the curved of the enemys walking path (depends on speed). We assume that the enemy walks in a constant line. Known variables: float projectilSpeed = 2000 m/s //speed of the projectile per second float gravitation = 9.81 m/s^2 //of cause the gravity lol D3DXVECTOR3 targetPosition //position of the target stored in a vector (x,y,z) D3DXVECTOR3 projectilePosition //position of the projectile D3DXVECTOR3 targetSpeed //stores the change of the targets position in the last second Variabledefinition ProjectilePosition at time of collision = ProjectilePos_t TargetPosition at time of collision = TargetPos_t ProjectilePosition at time 0, now = ProjectilePos_0 TargetPosition at time 0, now = TargetPos_0 Time to impact = t Aim-angle = theta My try: Found a formular to calculate "drop" (Drop of the projectile based on the gravity) on Wikipedia: float drop = 0.5f * gravity * t * t The speed of the projectile has a horizontal and a vertical part.. Found a formular for that on wikipedia aswell: ProjectilVelocity.x = projectilSpeed * cos(theta) ProjectilVelocity.y = projectilSpeed * sin(theta) So i would assume this is true for the projectile curve: ProjectilePos_t.x = ProjectilePos_0.x + ProjectileSpeed * t ProjectilePos_t.y = ProjectilePos_0.y + ProjectileSpeed * t + 0.5f * gravity * t * t ProjectilePos_t.z = ProjectilePos_0.z + ProjectileSpeed * t The target walk with a constant speed, so we can determine his curve by this: TargetPos_t = TargetPos_0 + TargetSpeed * D3DXVECTOR3(t, t, t) Now i dont know how to continue. I have to solve it somehow to get a hold on the time to impact somehow. As a basic formular i could use: float time = distanz / projectileSpeed But that wouldnt be truly correct as it would assume a linear "Trajectory". We just find this behaivor when using a rocket. I hope i was able to explain the problem as much as possible. If there are questions left, feel free to ask me! Greets from germany, Frank

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  • How to do the processing and keep GUI refreshed using databinding?

    - by macias
    History of the problem This is continuation of my previous question How to start a thread to keep GUI refreshed? but since Jon shed new light on the problem, I would have to completely rewrite original question, which would make that topic unreadable. So, new, very specific question. The problem Two pieces: CPU hungry heavy-weight processing as a library (back-end) WPF GUI with databinding which serves as monitor for the processing (front-end) Current situation -- library sends so many notifications about data changes that despite it works within its own thread it completely jams WPF data binding mechanism, and in result not only monitoring the data does not work (it is not refreshed) but entire GUI is frozen while processing the data. The aim -- well-designed, polished way to keep GUI up to date -- I am not saying it should display the data immediately (it can skip some changes even), but it cannot freeze while doing computation. Example This is simplified example, but it shows the problem. XAML part: <StackPanel Orientation="Vertical"> <Button Click="Button_Click">Start</Button> <TextBlock Text="{Binding Path=Counter}"/> </StackPanel> C# part (please NOTE this is one piece code, but there are two sections of it): public partial class MainWindow : Window,INotifyPropertyChanged { // GUI part public MainWindow() { InitializeComponent(); DataContext = this; } private void Button_Click(object sender, RoutedEventArgs e) { var thread = new Thread(doProcessing); thread.IsBackground = true; thread.Start(); } // this is non-GUI part -- do not mess with GUI here public event PropertyChangedEventHandler PropertyChanged; public void OnPropertyChanged(string property_name) { if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(property_name)); } long counter; public long Counter { get { return counter; } set { if (counter != value) { counter = value; OnPropertyChanged("Counter"); } } } void doProcessing() { var tmp = 10000.0; for (Counter = 0; Counter < 10000000; ++Counter) { if (Counter % 2 == 0) tmp = Math.Sqrt(tmp); else tmp = Math.Pow(tmp, 2.0); } } } Known workarounds (Please do not repost them as answers) Those two first are based on Jon ideas: pass GUI dispatcher to library and use it for sending notifications -- why it is ugly? because it could be no GUI at all give up with data binding COMPLETELY (one widget with databinding is enough for jamming), and instead check from time to time data and update the GUI manually -- well, I didn't learn WPF just to give up with it now ;-) and this is mine, it is ugly, but simplicity of it kills -- before sending notification freeze a thread -- Thread.Sleep(1) -- to let the potential receiver "breathe" -- it works, it is minimalistic, it is ugly though, and it ALWAYS slows down computation even if no GUI is there So... I am all ears for real solutions, not some tricks.

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  • In Ruby, how does coerce() actually work?

    - by Jian Lin
    It is said that when we have a class Point and knows how to perform point * 3 like the following: class Point def initialize(x,y) @x, @y = x, y end def *(c) Point.new(@x * c, @y * c) end end point = Point.new(1,2) p point p point * 3 Output: #<Point:0x336094 @x=1, @y=2> #<Point:0x335fa4 @x=3, @y=6> but then, 3 * point is not understood: Point can't be coerced into Fixnum (TypeError) So we need to further define an instance method coerce: class Point def coerce(something) [self, something] end end p 3 * point Output: #<Point:0x3c45a88 @x=3, @y=6> So it is said that 3 * point is the same as 3.*(point) that is, the instance method * takes an argument point and invoke on the object 3. Now, since this method * doesn't know how to multiply a point, so point.coerce(3) will be called, and get back an array: [point, 3] and then * is once again applied to it, is that true? point * 3 which is the same as point.*(3) and now, this is understood and we now have a new Point object, as performed by the instance method * of the Point class. The question is: 1) who invokes point.coerce(3) ? Is it Ruby automatically, or is it some code inside of * method of Fixnum by catching an exception? Or is it by case statement that when it doesn't know one of the known types, then call coerce? 2) Does coerce always need to return an array of 2 elements? Can it be no array? Or can it be an array of 3 elements? 3) And is the rule that, the original operator (or method) * will then be invoked on element 0, with the argument of element 1? (element 0 and element 1 are the two elements in that array returned by coerce) Who does it? Is it done by Ruby or is it done by code in Fixnum? If it is done by code in Fixnum, then it is a "convention" that everybody follows when doing a coerce? So could it be the code in * of Fixnum do something like this: if (something.typeof? ...) else if ... # other type else if ... # other type else # if it is not a type I know array = something.coerce(self) return array[0].*(array[1]) end

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  • Is there a scheduling algorithm that optimizes for "maker's schedules"?

    - by John Feminella
    You may be familiar with Paul Graham's essay, "Maker's Schedule, Manager's Schedule". The crux of the essay is that for creative and technical professionals, meetings are anathema to productivity, because they tend to lead to "schedule fragmentation", breaking up free time into chunks that are too small to acquire the focus needed to solve difficult problems. In my firm we've seen significant benefits by minimizing the amount of disruption caused, but the brute-force algorithm we use to decide schedules is not sophisticated enough to handle scheduling large groups of people well. (*) What I'm looking for is if there's are any well-known algorithms which minimize this productivity disruption, among a group of N makers and managers. In our model, There are N people. Each person pi is either a maker (Mk) or a manager (Mg). Each person has a schedule si. Everyone's schedule is H hours long. A schedule consists of a series of non-overlapping intervals si = [h1, ..., hj]. An interval is either free or busy. Two adjacent free intervals are equivalent to a single free interval that spans both. A maker's productivity is maximized when the number of free intervals is minimized. A manager's productivity is maximized when the total length of free intervals is maximized. Notice that if there are no meetings, both the makers and the managers experience optimum productivity. If meetings must be scheduled, then makers prefer that meetings happen back-to-back, while managers don't care where the meeting goes. Note that because all disruptions are treated as equally harmful to makers, there's no difference between a meeting that lasts 1 second and a meeting that lasts 3 hours if it segments the available free time. The problem is to decide how to schedule M different meetings involving arbitrary numbers of the N people, where each person in a given meeting must place a busy interval into their schedule such that it doesn't overlap with any other busy interval. For each meeting Mt the start time for the busy interval must be the same for all parties. Does an algorithm exist to solve this problem or one similar to it? My first thought was that this looks really similar to defragmentation (minimize number of distinct chunks), and there are a lot of algorithms about that. But defragmentation doesn't have much to do with scheduling. Thoughts? (*) Practically speaking this is not really a problem, because it's rare that we have meetings with more than ~5 people at once, so the space of possibilities is small.

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  • Zero code coverage with cobertura 1.9.2 but tests are working

    - by eraonel
    I run the code coverage target: <junit fork="yes" dir="${basedir}" failureProperty="test.failed"> <!-- Note the classpath order: instrumented classes are before the original (uninstrumented) classes. This is important. --> <classpath path="${instrumented.dir}" /> <classpath path="${classes.dir}" /> <classpath refid="classpath" /> <!-- The instrumented classes reference classes used by the Cobertura runtime, so Cobertura and its dependencies must be on your classpath. --> <classpath refid="cobertura.classpath" /> <formatter type="xml" /> <!--<test name="${testcase}" todir="${reports.xml.dir}" if="testcase" />--> <batchtest fork="yes" todir="${reports.xml.dir}"> <fileset dir="${classes.dir}"> <include name="**/generated/AllTests.class" /> </fileset> </batchtest> </junit> <junitreport todir="${reports.xml.dir}"> <fileset dir="${reports.xml.dir}"> <include name="TEST-*.xml" /> </fileset> <report format="frames" todir="${reports.html.dir}" /> </junitreport> Then I get the following output ( when using fork="true"): java.lang.reflect.InvocationTargetException 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:585) at net.sourceforge.cobertura.util.FileLocker.lock(FileLocker.java:124) at net.sourceforge.cobertura.coveragedata.ProjectData.saveGlobalProjectData(ProjectData.java:331) at net.sourceforge.cobertura.coveragedata.SaveTimer.run(SaveTimer.java:31) at java.lang.Thread.run(Thread.java:595) Caused by: java.io.IOException: No locks available at sun.nio.ch.FileChannelImpl.lock0(Native Method) at sun.nio.ch.FileChannelImpl.lock(FileChannelImpl.java:784) at java.nio.channels.FileChannel.lock(FileChannel.java:865) ... 8 more --------------------------------------- Unable to get lock on /vobs/rnc/rrt/roam2/roamSs/RoamMao_swb/RoamMao_bldu/ant_build/cobertura.ser.lock: null This is known to happen on Linux kernel 2.6.20. Make sure cobertura.jar is in the root classpath of the jvm process running the instrumented code. If the instrumented code is running in a web server, this means cobertura.jar should be in the web server's lib directory. Don't put multiple copies of cobertura.jar in different WEB-INF/lib directories. Only one classloader should load cobertura. It should be the root classloader. I am using Ant 1.7.0 and cobertura 1.9.2. Any ideas why there is no coverage? Test run ok as I see in my target. I have tried to switch java versions ( 1.5.0_06 and 1.6.0_10) but no difference.

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  • Coroutines in Java

    - by JUST MY correct OPINION
    I would like to do some stuff in Java that would be clearer if written using concurrent routines, but for which full-on threads are serious overkill. The answer, of course, is the use of coroutines, but there doesn't appear to be any coroutine support in the standard Java libraries and a quick Google on it brings up tantalising hints here or there, but nothing substantial. Here's what I've found so far: JSIM has a coroutine class, but it looks pretty heavyweight and conflates, seemingly, with threads at points. The point of this is to reduce the complexity of full-on threading, not to add to it. Further I'm not sure that the class can be extracted from the library and used independently. Xalan has a coroutine set class that does coroutine-like stuff, but again it's dubious if this can be meaningfully extracted from the overall library. It also looks like it's implemented as a tightly-controlled form of thread pool, not as actual coroutines. There's a Google Code project which looks like what I'm after, but if anything it looks more heavyweight than using threads would be. I'm basically nervous of something that requires software to dynamically change the JVM bytecode at runtime to do its work. This looks like overkill and like something that will cause more problems than coroutines would solve. Further it looks like it doesn't implement the whole coroutine concept. By my glance-over it gives a yield feature that just returns to the invoker. Proper coroutines allow yields to transfer control to any known coroutine directly. Basically this library, heavyweight and scary as it is, only gives you support for iterators, not fully-general coroutines. The promisingly-named Coroutine for Java fails because it's a platform-specific (obviously using JNI) solution. And that's about all I've found. I know about the native JVM support for coroutines in the Da Vinci Machine and I also know about the JNI continuations trick for doing this. These are not really good solutions for me, however, as I would not necessarily have control over which VM or platform my code would run on. (Indeed any bytecode manipulation system would suffer similar problems -- it would be best were this pure Java if possible. Runtime bytecode manipulation would restrict me from using this on Android, for example.) So does anybody have any pointers? Is this even possible? If not, will it be possible in Java 7?

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  • Large File Download - Connection With Server Reset

    - by daveywc
    I have an asp.net website that allows the user to download largish files - 30mb to about 60mb. Sometimes the download works fine but often it fails at some varying point before the download finishes with the message saying that the connection with the server was reset. Originally I was simply using Server.TransmitFile but after reading up a bit I am now using the code posted below. I am also setting the Server.ScriptTimeout value to 3600 in the Page_Init event. private void DownloadFile(string fname, bool forceDownload) { string path = MapPath(fname); string name = Path.GetFileName(path); string ext = Path.GetExtension(path); string type = ""; // set known types based on file extension if (ext != null) { switch (ext.ToLower()) { case ".mp3": type = "audio/mpeg"; break; case ".htm": case ".html": type = "text/HTML"; break; case ".txt": type = "text/plain"; break; case ".doc": case ".rtf": type = "Application/msword"; break; } } if (forceDownload) { Response.AppendHeader("content-disposition", "attachment; filename=" + name.Replace(" ", "_")); } if (type != "") { Response.ContentType = type; } else { Response.ContentType = "application/x-msdownload"; } System.IO.Stream iStream = null; // Buffer to read 10K bytes in chunk: byte[] buffer = new Byte[10000]; // Length of the file: int length; // Total bytes to read: long dataToRead; try { // Open the file. iStream = new System.IO.FileStream(path, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read); // Total bytes to read: dataToRead = iStream.Length; //Response.ContentType = "application/octet-stream"; //Response.AddHeader("Content-Disposition", "attachment; filename=" + filename); // Read the bytes. while (dataToRead > 0) { // Verify that the client is connected. if (Response.IsClientConnected) { // Read the data in buffer. length = iStream.Read(buffer, 0, 10000); // Write the data to the current output stream. Response.OutputStream.Write(buffer, 0, length); // Flush the data to the HTML output. Response.Flush(); buffer = new Byte[10000]; dataToRead = dataToRead - length; } else { //prevent infinite loop if user disconnects dataToRead = -1; } } } catch (Exception ex) { // Trap the error, if any. Response.Write("Error : " + ex.Message); } finally { if (iStream != null) { //Close the file. iStream.Close(); } Response.Close(); } }

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  • translating specifications into query predicates

    - by Jeroen
    I'm trying to find a nice and elegant way to query database content based on DDD "specifications". In domain driven design, a specification is used to check if some object, also known as the candidate, is compliant to a (domain specific) requirement. For example, the specification 'IsTaskDone' goes like: class IsTaskDone extends Specification<Task> { boolean isSatisfiedBy(Task candidate) { return candidate.isDone(); } } The above specification can be used for many purposes, e.g. it can be used to validate if a task has been completed, or to filter all completed tasks from a collection. However, I want to re-use this, nice, domain related specification to query on the database. Of course, the easiest solution would be to retrieve all entities of our desired type from the database, and filter that list in-memory by looping and removing non-matching entities. But clearly that would not be optimal for performance, especially when the entity count in our db increases. Proposal So my idea is to create a 'ConversionManager' that translates my specification into a persistence technique specific criteria, think of the JPA predicate class. The services looks as follows: public interface JpaSpecificationConversionManager { <T> Predicate getPredicateFor(Specification<T> specification, Root<T> root, CriteriaQuery<?> cq, CriteriaBuilder cb); JpaSpecificationConversionManager registerConverter(JpaSpecificationConverter<?, ?> converter); } By using our manager, the users can register their own conversion logic, isolating the domain related specification from persistence specific logic. To minimize the configuration of our manager, I want to use annotations on my converter classes, allowing the manager to automatically register those converters. JPA repository implementations could then use my manager, via dependency injection, to offer a find by specification method. Providing a find by specification should drastically reduce the number of methods on our repository interface. In theory, this all sounds decent, but I feel like I'm missing something critical. What do you guys think of my proposal, does it comply to the DDD way of thinking? Or is there already a framework that does something identical to what I just described?

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  • XmlHttpRequest bug?

    - by valdo
    Hello all. I'm writing a program that among other things needs to download a file given its URL. I'm too lazy to implement the Http/Https protocols manually, so that I needed some library/object/function that'll do the job. Critical requirement: The download must be asynchronous. That is, the thread that issued the download must be able to do something else "while" downloading the file, plus the download must be able to be aborted anytime without any barbaric side effects (such as internal call to TerminateThread). Nice-to-have requirements: Should be able to download the file "into memory". Means - read the contents of the file as they arrive, not necessarily save it into some "file system" file. It'd be nice to have some convenient Win32 progress notification mechanism (waitable event, semahpore, completion port, etc.), rather than just periodically polling the download status. I've chosen the XmlHttpRequest COM object to do the work. It seemed to work fine enough, plus it supported asynchronous mode. However I noticed that after some period it just stops working. That is, after several successful file downloads it stops downloading anything. I periodically poll it to get its status, it reports "in-progress", but nothing actually happens, and there's no network activity. Moreover, when the same process creates another instance of XmlHttpRequest object to perform new downloads - the effect is the same. The object reports "in progress", whereas it doesn't even try to connect to the server (according to network sniffers and system TCP state). The only way to make this object work back is to restart the process. This makes me suspect that there's a sort of a bug (sorry, I meant undocumented feature) in the object. Also it's not a bug at the level of an individual object, since the problem persists when the object is destroyed and another one is created. It's probably some global state of the DLL that implements this object. Does anyone know something about this? Is this a known bug? I'm pretty sure there's no chance that I have another bug in my code, because of which it seems to me to be the bug is in the XmlHttpRequest. I've done enoughtests and spent time with the debugger to conclude without reasonable doubt that it's just the object stops working. BTW, while the object should work, I do all the waiting via MsgWaitXXXX API calls. So that if this object needs the message loop to work properly (for instance, it may create a hidden notification window and bind it to a socket via WSAAsyncSelect) - I give it the opportunity.

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  • How can I get jquery to toggle-fade a flashcard div open and closed on click?

    - by Edward Tanguay
    What do I have to change to the code below in order for the user to click on a flashcard header to open and close the flashcard answer? I couldn't get toggle() to work with fadein/fadeout the version below doesn't respond to the click code: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <script type="text/javascript" src="http://www.google.com/jsapi"></script> <script type="text/javascript"> google.load("jquery", "1.4.1"); google.setOnLoadCallback(function() { $("div > div.question").click(function() { if($(this).next().is(":hidden") { $(this).next().fadeIn("slow"); } else { $(this).next().fadeOut("slow"); } }); }); </script> <style> div.flashcard { margin: 0 10px 10px 0; } div.flashcard div.question { background-color:#ddd; width: 400px; padding: 5px; cursor: hand; cursor: pointer; } div.flashcard div.answer { background-color:#eee; width: 400px; padding: 5px; display: none; } </style> </head> <body> <div id="1" class="flashcard"> <div class="question">Who was Wagner?</div> <div class="answer">German composer, conductor, theatre director and essayist, primarily known for his operas (or "music dramas", as they were later called). Unlike most other opera composers, Wagner wrote both the music and libretto for every one of his works.</div> </div> <div id="2" class="flashcard"> <div class="question">Who was Thalberg?</div> <div class="answer">a composer and one of the most distinguished virtuoso pianists of the 19th century.</div> </div> </body> </html>

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  • Quick question regarding this issue, Why doesnt it print out the second value(converted second value

    - by sil3nt
    Quick question, What have I done wrong here. The purpose of this code is to get the input into a string, the input being "12 34", with a space in between the "12" and "32" and to convert and print the two separate numbers from an integer variable known as number. Why doesn't the second call to the function copyTemp, not produce the value 34?. I have an index_counter variable which keeps track of the string index and its meant to skip the 'space' character?? what have i done wrong? thanks. #include <stdio.h> #include <string.h> int index_counter = 0; int number; void copyTemp(char *expr,char *temp); int main(){ char exprstn[80]; //as global? char tempstr[80]; gets(exprstn); copyTemp(exprstn,tempstr); printf("Expression: %s\n",exprstn); printf("Temporary: %s\n",tempstr); printf("number is: %d\n",number); copyTemp(exprstn,tempstr); //second call produces same output shouldnt it now produce 34 in the variable number? printf("Expression: %s\n",exprstn); printf("Temporary: %s\n",tempstr); printf("number is: %d\n",number); return 0; } void copyTemp(char *expr,char *temp){ int i; for(i = index_counter; expr[i] != '\0'; i++){ if (expr[i] == '0'){ temp[i] = expr[i]; } if (expr[i] == '1'){ temp[i] = expr[i]; } if (expr[i] == '2'){ temp[i] = expr[i]; } if (expr[i] == '3'){ temp[i] = expr[i]; } if (expr[i] == '4'){ temp[i] = expr[i]; } if (expr[i] == '5'){ temp[i] = expr[i]; } if (expr[i] == '6'){ temp[i] = expr[i]; } if (expr[i] == '7'){ temp[i] = expr[i]; } if (expr[i] == '8'){ temp[i] = expr[i]; } if (expr[i] == '9'){ temp[i] = expr[i]; } if (expr[i] == ' '){ temp[i] = '\0'; sscanf(temp,"%d",&number); index_counter = i+1; //skips? } } // is this included here? temp[i] = '\0'; }

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  • Calculating rotation and translation matrices between two odometry positions for monocular linear triangulation

    - by user1298891
    Recently I've been trying to implement a system to identify and triangulate the 3D position of an object in a robotic system. The general outline of the process goes as follows: Identify the object using SURF matching, from a set of "training" images to the actual live feed from the camera Move/rotate the robot a certain amount Identify the object using SURF again in this new view Now I have: a set of corresponding 2D points (same object from the two different views), two odometry locations (position + orientation), and camera intrinsics (focal length, principal point, etc.) since it's been calibrated beforehand, so I should be able to create the 2 projection matrices and triangulate using a basic linear triangulation method as in Hartley & Zissermann's book Multiple View Geometry, pg. 312. Solve the AX = 0 equation for each of the corresponding 2D points, then take the average In practice, the triangulation only works when there's almost no change in rotation; if the robot even rotates a slight bit while moving (due to e.g. wheel slippage) then the estimate is way off. This also applies for simulation. Since I can only post two hyperlinks, here's a link to a page with images from the simulation (on the map, the red square is simulated robot position and orientation, and the yellow square is estimated position of the object using linear triangulation.) So you can see that the estimate is thrown way off even by a little rotation, as in Position 2 on that page (that was 15 degrees; if I rotate it any more then the estimate is completely off the map), even in a simulated environment where a perfect calibration matrix is known. In a real environment when I actually move around with the robot, it's worse. There aren't any problems with obtaining point correspondences, nor with actually solving the AX = 0 equation once I compute the A matrix, so I figure it probably has to do with how I'm setting up the two camera projection matrices, specifically how I'm calculating the translation and rotation matrices from the position/orientation info I have relative to the world frame. How I'm doing that right now is: Rotation matrix is composed by creating a 1x3 matrix [0, (change in orientation angle), 0] and then converting that to a 3x3 one using OpenCV's Rodrigues function Translation matrix is composed by rotating the two points (start angle) degrees and then subtracting the final position from the initial position, in order to get the robot's straight and lateral movement relative to its starting orientation Which results in the first projection matrix being K [I | 0] and the second being K [R | T], with R and T calculated as described above. Is there anything I'm doing really wrong here? Or could it possibly be some other problem? Any help would be greatly appreciated.

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  • Thin & Sinatra not taking port

    - by NekoNova
    I'm having problems settig up my application using Thin and Sinatra. I have created a development-config.ru file that contains the following settings: # This is a rack configuration file to fire up the Sinatra application. # This allows better control and configuration as we are using the modular # approach here for controlling our application. # # Extend the Ruby load path with the root of the API and the lib folder # so that we can automatically include all our own custom classes. This makes # the requiring of files a bit cleaner and easier to maintain. # This is basically what rails does as well. # We also store the root of the API in the ENV settings to ensure we have # always access to the root of the API when building paths. ENV['API_ROOT'] = File.dirname(__FILE__) $:.unshift ENV['API_ROOT'] $:.unshift File.expand_path(File.join(ENV['API_ROOT'], 'lib')) $:.unshift File.expand_path(File.join(ENV['API_ROOT'], 'db')) # Now we can require all the gems used for the entire API by simpling requiring # them here. We can also include the classes that we have defined inside the lib # folder. require 'rubygems' require 'bundler' # Run Bundler to setup our gems properly. This will install all the missing gems on # the system and ensure that the deployment environment is ready to run. Bundler.require # To make the loading easier for the application, we will now automatically load all # models that have been defined inside the lib folder. This ensures that we do not need # to load them anymore anywhere else in our application, as the models will be known to # ruby everywhere. Dir.glob(File.join(ENV['API_ROOT'], 'lib', '**', '*.rb')).each{|file| require file} # Now we will configure the Sinatra application so that we can fire up the entire API. # This requires some detailed settings like whether logging is allowed, the port to be # used and some folder locations. require 'sinatra' require 'app' set :logging, true set :dump_errors, true set :port, 3001 set :views, "#{ENV['API_ROOT']}/views" set :public_folder, "#{ENV['API_ROOT']}/public" set :environment, :test # Start up the Sinatra application with all the settings that we have defined. run App.new This is based upon the information I found on the Sinatra website. However, the problem is that I cannot get the application running on port 3001. If I use thin start -R development-config.ru it runs on port 3000. If I use rackup config-development.ru it runs on port 9696. However I never see Sinatra kick in or run over port 3000. My application looks like this: # Author : Arne De Herdt # Email : # This is the actuall application that will be running under Sinatra # to serve the requests for the billing middleware API. # We use the modular approach here to allow control when deploying # the application using Capistrano. require 'sinatra/base' require 'logger' require 'savon' require 'billcrux' class App < Sinatra::Base # This action responds to POST requests on the URI '/billcrux/register' # and is responsible for handeling registration requests with the # BillCrux payment system. # The post "/billcrux/register" do # do stuff end end Can someone tell me what I am doing wrong?

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