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• Performance issues when using SSD for a developer notebook (WAMP/LAMP stack)?

  - by András Szepesházi

  I'm a web application developer using my notebook as a standalone development environment (WAMP stack). I just switched from a Core2-duo Vista 32 bit notebook with 2Gb RAM and SATA HDD, to an i5-2520M Win7 64 bit with 4Gb RAM and 128 GB SDD (Corsair P3 128). My initial experience was what I expected, fast boot, quick load of all the applications (Eclipse takes now 5 seconds as opposed to 30s on my old notebook), overall great experience. Then I started to build up my development stack, both as LAMP (using VirtualBox with a debian guest) and WAMP (windows native apache + mysql + php). I wanted to compare those two. This still all worked great out, then I started to pull in my projects to these stacks. And here came the nasty surprise, one of those projects produced a lot worse response times than on my old notebook (that was true for both the VirtualBox and WAMP stack). Apache, php and mysql configurations were practically identical in all environments. I started to do a lot of benchmarking and profiling, and here is what I've found: All general benchmarks (Performance Test 7.0, HDTune Pro, wPrime2 and some more) gave a big advantage to the new notebook. Nothing surprising here. Disc specific tests showed that read/write operations peaked around 380M/160M for the SSD, and all the different sized block operations also performed very well. Started apache performance benchmarking with Apache Benchmark for a small static html file (10 concurrent threads, 500 iterations). Old notebook: min 47ms, median 111ms, max 156ms New WAMP stack: min 71ms, median 135ms, max 296ms New LAMP stack (in VirtualBox): min 6ms, median 46ms, max 175ms Right here I don't get why the native WAMP stack performed so bad, but at least the LAMP environment brought the expected speed. Apache performance measurement for non-cached php content. The php runs a loop of 1000 and generates sha1(uniqid()) inisde. Again, 10 concurrent threads, 500 iterations were used for the benchmark. Old notebook: min 0ms, median 39ms, max 218ms New WAMP stack: min 20ms, median 61ms, max 186ms New LAMP stack (in VirtualBox): min 124ms, median 704ms, max 2463ms What the hell? The new LAMP performed miserably, and even the new native WAMP was outperformed by the old notebook. php + mysql test. The test consists of connecting to a database and reading a single record form a table using INNER JOIN on 3 more (indexed) tables, repeated 100 times within a loop. Databases were identical. 10 concurrent threads, 100 iterations were used for the benchmark. Old notebook: min 1201ms, median 1734ms, max 3728ms New WAMP stack: min 367ms, median 675ms, max 1893ms New LAMP stack (in VirtualBox): min 1410ms, median 3659ms, max 5045ms And the same test with concurrency set to 1 (instead of 10): Old notebook: min 1201ms, median 1261ms, max 1357ms New WAMP stack: min 399ms, median 483ms, max 539ms New LAMP stack (in VirtualBox): min 285ms, median 348ms, max 444ms Strictly for my purposes, as I'm using a self contained development environment (= low concurrency) I could be satisfied with the second test's result. Though I have no idea why the VirtualBox environment performed so bad with higher concurrency. Finally I performed a test of including many php files. The application that I mentioned at the beginning, the one that was performing so bad, has a heavy bootstrap, loads hundreds of small library and configuration files while initializing. So this test does nothing else just includes about 100 files. Concurrency set to 1, 100 iterations: Old notebook: min 140ms, median 168ms, max 406ms New WAMP stack: min 434ms, median 488ms, max 604ms New LAMP stack (in VirtualBox): min 413ms, median 1040ms, max 1921ms Even if I consider that VirtualBox reached those files via shared folders, and that slows things down a bit, I still don't see how could the old notebook outperform so heavily both new configurations. And I think this is the real root of the slow performance, as the application uses even more includes, and the whole bootstrap will occur several times within a page request (for each ajax call, for example). To sum it up, here I am with a brand new high-performance notebook that loads the same page in 20 seconds, that my old notebook can do in 5-7 seconds. Needless to say, I'm not a very happy person right now. Why do you think I experience these poor performance values? What are my options to remedy this situation?

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• Does a servlet-based stack have significant overheads?

  - by John

  I don't know if it's simply because page-loads take a little time, or the way servlets have an abstraction framework above the 'bare metal' of HTTP, or just because of the "Enterprise" in Jave-EE, but in my head I have the notion that a servlet-based app is inherently adding overhead compared to a Java app which simply deals with sockets directly. Forget web-pages, imagine instead a Java server app where you send it a question over an HTTP request and it looks up an answer from memory and returns the answer in the response. You can easily write a Java socket-based app which does this, you can also do a servlet approach and get away from the "bare metal" of sockets. Is there any measurable performance impact to be expected implementing the same approach using Servlets rather than a custom socket-based HTTP listening app? And yes, I am hazy on the exact data sent in HTTP requests and I know it's a vague question. It's really about whether servlet implementations have lots of layers of indirection or anything else that would add up to a significant overhead per call, where by significant I mean maybe an additional 0.1s or more.

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• Token based Authentication for WCF HTTP/REST Services: Authorization

  - by Your DisplayName here!

  In the previous post I showed how token based authentication can be implemented for WCF HTTP based services. Authentication is the process of finding out who the user is – this includes anonymous users. Then it is up to the service to decide under which circumstances the client has access to the service as a whole or individual operations. This is called authorization. By default – my framework does not allow anonymous users and will deny access right in the service authorization manager. You can however turn anonymous access on – that means technically, that instead of denying access, an anonymous principal is placed on Thread.CurrentPrincipal. You can flip that switch in the configuration class that you can pass into the service host/factory. var configuration = new WebTokenWebServiceHostConfiguration {     AllowAnonymousAccess = true }; But this is not enough, in addition you also need to decorate the individual operations to allow anonymous access as well, e.g.: [AllowAnonymousAccess] public string GetInfo() {     ... } Inside these operations you might have an authenticated or an anonymous principal on Thread.CurrentPrincipal, and it is up to your code to decide what to do. Side note: Being a security guy, I like this opt-in approach to anonymous access much better that all those opt-out approaches out there (like the Authorize attribute – or this.). Claims-based Authorization Since there is a ClaimsPrincipal available, you can use the standard WIF claims authorization manager infrastructure – either declaratively via ClaimsPrincipalPermission or programmatically (see also here). [ClaimsPrincipalPermission(SecurityAction.Demand,     Resource = "Claims",     Operation = "View")] public ViewClaims GetClientIdentity() {     return new ServiceLogic().GetClaims(); }   In addition you can also turn off per-request authorization (see here for background) via the config and just use the “domain specific” instrumentation. While the code is not 100% done – you can download the current solution here. HTH (Wanna learn more about federation, WIF, claims, tokens etc.? Click here.)

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• How to implement friction in a physics engine based on "Advanced Character Physics"

  - by paldepind

  I have implemented a physics engine based on the concepts in the classic text Advanced Character Physics by Thomas Jakobsen. Friction is only discussed very briefly in the article and Jakobsen himself notes how "other and better friction models than this could and should be implemented." Generally how could one implement a believable friction model on top of the concepts from the mentioned article? And how could the found friction be translated into rotation on a circle? I do not want this question to be about my specific implementation but about how to combine Jakobsens ideas with a great friction system more generally. But here is a live demo showing the current state of my engine which does not handle friction in any way: http://jsfiddle.net/Z7ECB/embedded/result/ Below is a picture showing and example on how collision detection could work in an engine based in the paper. In the Verlet integration the current and previous position is always stored. Based on these a new position is calculated. In every frame I calculate the distance between the circles and the lines. If this distance is less than a circles radius a collision has occurred and the circle is projected perpendicular out of the offending line according to the size of the overlap (offset on the picture). Velocity is implicit due to Verlet integration so changing position also changes the velocity. What I need to do know is to somehow determine the amount of friction on the circle and move it backwards parallel to the line in order to reduce its speed.

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• Examples of permission-based authorization systems in .Net?

  - by Rachel

  I'm trying to figure out how to do roles/permissions in our application, and I am wondering if anyone knows of a good place to get a list of different permission-based authorization systems (preferably with code samples) and perhaps a list of pros/cons for each method. I've seen examples using simple dictionaries, custom attributes, claims-based authorization, and custom frameworks, but I can't find a simple explanation of when to use one over another and what the pros/cons are to using each method. (I'm sure there's other ways than the ones I've listed....) I have never done anything complex with permissions/authorization before, so all of this seems a little overwhelming to me and I'm having trouble figuring out what what is useful information that I can use and what isn't. What I DO know is that this is for a Windows environment using C#/WPF and WCF services. Some permission checks are done on the WCF service and some on the client. Some are business rules, some are authorization checks, and others are UI-related (such as what forms a user can see). They can be very generic like boolean or numeric values, or they can be more complex such as a range of values or a list of database items to be checked/unchecked. Permissions can be set on the group-level, user-level, branch-level, or a custom level, so I do not want to use role-based authorization. Users can be in multiple groups, and users with the appropriate authorization are in charge of creating/maintaining these groups. It is not uncommon for new groups to be created, so they can't be hard-coded.

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• Rotate canvas along its center based on user touch - Android

  - by Ganapathy

  I want to rotate the canvas circularly on its center axis based on user touch. i want to rotate based on center but its rotating based on top left corner . so i am able to see only 1/4 for rotation of image. any idea.. Like a old phone dialer . I have tried like as follows onDraw(Canvas canvas){ canvas.save(); // do my rotation canvas.rotate(rotation,0,0); canvas.drawBitmap( ((BitmapDrawable)d).getBitmap(),0,0,p ); canvas.restore(); } @Override public boolean onTouchEvent(MotionEvent e) { float x = e.getX(); float y = e.getY(); updateRotation(x,y); mPreviousX = x; mPreviousY = y; invalidate(); } private void updateRotation(float x, float y) { double r = Math.atan2(x - centerX, centerY - y); rotation = (int) Math.toDegrees(r); }

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• Generating grammatically correct MUD-style attack descriptions

  - by Extrakun

  I am currently working on a text based game, where the outcome of a combat round goes something like this %attacker% inflicts a serious wound (12 points damage) on %defender% Right now, I just swap %attacker% with the name of the attacker, and %defender% for the name of the defender. However, the description works, but don't read correctly. Since the game is just all text, I don't want to resort to generic descriptions (Such as "You use Attack on Goblin for 5 damage", which arguably solve the problem) How do I generate correct descriptions for cases where %attacker% refers to "You", the player? "You inflicts..." is wrong "Bees", or other plural? I need somehow to know I should prefix the name with a "The " If %attacker% is a generic noun, such as "Goblin", it will read weird as opposed to %attacker% being a name. Compare "Goblin inflicts..." vs. "Aldraic Swordbringer inflicts...." How does text-based games usually resolve such issues?

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• How Would I create alternate players (Turn base Event)

  - by Blue

  The picture above shows 2 players. Each containing 3 characters. I want to know how to make a Turn based event starting with player 1 alternating turns with player 2. And in every alternation each character gets a turn. If a character dies, the next character on the same team goes, and so on. How would I create this? Is there a tutorial? I haven't made any turn-based games so I don't know how to program these kinds of stuff.

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• What is realism?

  - by eversor

  Beyond the obvious something that seams real, realism in games is a hard feature to hit. In some cases, things that are completely impossible in real life are seen as realistic by gamers. For instance, in some FPS you can survive being hit by a fair amount of bullets when in real life one is enough, Newton-defying car drifts, etc. So, in some cases, reductions of life-like actions or consequences implies a bigger sense of realism. The root of this pseudo-philosophical question lies in: I am going to create a engine for battles in an online (browser-based) strategic game. Browser-based means that the battle would not be seen. And i do not know how to approach this realism issue.

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• Stack Overflow problem in a recursive program in C

  - by Adi

  Hi all, I am getting a stack overflow in one of the recursive functions i am running.. Here is the code.. void* buddyMalloc(int req_size) { // Do something here return buddy_findout(original_index,req_size); // This is the recursive call } void *buddy_findout(int current_index,int req_size) { char *selected = NULL; if(front!=NULL) { if(current_index==original_index) { // Do something here return selected; } else { // Do Something here return buddy_findout(current_index+1,req_size); } } else { return buddy_findout(current_index-1,req_size); } } Consider the initial value of index to be 4. and it first do index-1 till it reaches 0 index. and then it comes back to index 4 by incrementing..This is wht i want to implement. But it gives a stack overflow with memory map in the command prompt : Here is the output from my shell : * glibc detected * ./473_mem: free(): invalid pointer: 0x00c274c0 * ======= Backtrace: ========= /lib/tls/i686/cmov/libc.so.6[0xb50ff1] /lib/tls/i686/cmov/libc.so.6[0xb526f2] /lib/tls/i686/cmov/libc.so.6(cfree+0x6d)[0xb557cd] ./473_mem[0x8048b44] ./473_mem[0x8048b74] ./473_mem[0x8048b74] ./473_mem[0x8048944] ./473_mem[0x8048c87] ./473_mem[0x8048d31] ./473_mem[0x8048f79] /lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xe6)[0xafcb56] ./473_mem[0x8048671] ======= Memory map: ======== 0017c000-00198000 r-xp 00000000 08:01 5224 /lib/libgcc_s.so.1 00198000-00199000 r--p 0001b000 08:01 5224 /lib/libgcc_s.so.1 00199000-0019a000 rw-p 0001c000 08:01 5224 /lib/libgcc_s.so.1 00260000-00284000 r-xp 00000000 08:01 1927 /lib/tls/i686/cmov/libm-2.10.1.so 00284000-00285000 r--p 00023000 08:01 1927 /lib/tls/i686/cmov/libm-2.10.1.so 00285000-00286000 rw-p 00024000 08:01 1927 /lib/tls/i686/cmov/libm-2.10.1.so 006cd000-006e8000 r-xp 00000000 08:01 6662 /lib/ld-2.10.1.so 006e8000-006e9000 r--p 0001a000 08:01 6662 /lib/ld-2.10.1.so 006e9000-006ea000 rw-p 0001b000 08:01 6662 /lib/ld-2.10.1.so 00aa9000-00aaa000 r-xp 00000000 00:00 0 [vdso] 00ae6000-00c24000 r-xp 00000000 08:01 1900 /lib/tls/i686/cmov/libc-2.10.1.so 00c24000-00c25000 ---p 0013e000 08:01 1900 /lib/tls/i686/cmov/libc-2.10.1.so 00c25000-00c27000 r--p 0013e000 08:01 1900 /lib/tls/i686/cmov/libc-2.10.1.so 00c27000-00c28000 rw-p 00140000 08:01 1900 /lib/tls/i686/cmov/libc-2.10.1.so 00c28000-00c2b000 rw-p 00000000 00:00 0 08048000-0804a000 r-xp 00000000 00:14 2176 /media/windows-share/OS/Project2/473_mem 0804a000-0804b000 r--p 00001000 00:14 2176 /media/windows-share/OS/Project2/473_mem 0804b000-0804c000 rw-p 00002000 00:14 2176 /media/windows-share/OS/Project2/473_mem 08483000-084a4000 rw-p 00000000 00:00 0 [heap] b7600000-b7621000 rw-p 00000000 00:00 0 b7621000-b7700000 ---p 00000000 00:00 0 b7716000-b7819000 rw-p 00000000 00:00 0 b7827000-b782a000 rw-p 00000000 00:00 0 bfb96000-bfbab000 rw-p 00000000 00:00 0 [stack] Aborted Thanks in advance adi

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• Android - Calling getJSONArray throwing JSONException with no stack trace

  - by Agathron

  Hi all, I'm currently working on an android app that pulls a list of forums from a JSON feed. I'm trying to parse the feed and immediately upon calling getJSONArray a JSON exception is being thrown with no stack trace. The JSON being returned is stored in an JSONObject jobj with the format as follows: { "Forum": [ {"ForumName":"CEC Employee Communications Forum","ForumId":"105"}, {"ForumName":"CEC External Stakeholder Relations Forum","ForumId":"109"}, {"ForumName":"See All...","ForumId":"0"} ] } However when running the following code, I get an immediate exception without a stack trace: JSONArray jarray = new JSONArray(); jarray = jobj.getJSONArray("Forum"); Running jobj.GetJSONArray("Forum").toString(); returns what looks to be a correct array of the format: [ {"ForumName":"CEC Employee Communications Forum","ForumId":"105"}, {"ForumName":"CEC External Stakeholder Relations Forum","ForumId":"109"}, {"ForumName":"See All...","ForumId":"0"} ] I also tried JSONArray jarray = new JSONArray(jobj.GetJSONArray("Forum").toString()); and had the exception thrown immediately. Any help would be greatly appreciated. Thanks!

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• XCode 3.2.1 and Instruments: Useless Stack Trace

  - by Jason George

  I've reached the stage where it's time to start tracking down memory leaks and, to my dismay, Instruments is giving me very little to go on (other than the fact that I definitely have leaks). My stack trace contains no information other than memory addresses. Since I'm working on a new project and I've transitioned to version 3.2.1 of XCode in tandem, I'm not sure if it's my program configuration or XCode that's causing the problem. I have found one reference to the issue coupled with a post on the dyld leak that seems to be prevalent with the 3.2.1 release. Since I haven't been able to find much on the problem I'm guessing it's something I've created rather than a systematic issue with XCode. If someone has any idea where I might have thrown a wrench in the works, I would love some pointers. Also, if someone could just verify that the stack trace is indeed functioning properly in 3.2.1 that would be useful as well.

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• activities stack

  - by klaus-vlad

  Is there a way to vizualise the activity stack, at some moment during debug, or normal run ?

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• Ur mom is so fat

  - by FuckThisShit

  the recursive function to calculate her mass causes a stack overflow

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• Stack Allocation in C

  - by JT

  Is it bad style to design your simple C programs to allocate everything, or most everything, on the stack?

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• OpenID like Stack Overflow

  - by eWolf

  I want to create an OpenID login with PHP just like it can be found on Stack Overflow. I know there are many questions for this, but mine is different. If I understood it correctly, every OpenID is defined by a unique URL. But: If I hit the Google button on the Stack Overflow login page, one generic URL is inserted in the text field. Is this the direct URL to the OpenID server? And if it is, how do I have to pass the URL to this class?

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• How does a virtual machine work?

  - by Martin

  I've been looking into how programming languages work, and some of them have a so-called virtual machines. I understand that this is some form of emulation of the programming language within another programming language, and that it works like how a compiled language would be executed, with a stack. Did I get that right? With the proviso that I did, what bamboozles me is that many non-compiled languages allow variables with "liberal" type systems. In Python for example, I can write this: x = "Hello world!" x = 2**1000 Strings and big integers are completely unrelated and occupy different amounts of space in memory, so how can this code even be represented in a stack-based environment? What exactly happens here? Is x pointed to a new place on the stack and the old string data left unreferenced? Do these languages not use a stack? If not, how do they represent variables internally?

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• Assembly stack persistency

  - by user246100

  Hello. I would like to know if after calling functions the data I have in the stack is persistent. Like, I would like to know if (assuming cdecl convention) can I do this (independently of function X and independently of optimizations): push 1 push 2 push 3 call X call X call X add 12 esp ? Also, let's say that before the calls I save the address of where the pushed values are in a global variable. Can I, inside X, alter the values it contain by acessing the global variable? Like, for some reason I want that in X I'm able to alter the values in stack so that the second and third call to X receive different values.

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• Tomcat - virtualhosting - name / ip / port - based

  - by lisak

  Hey, what are the usage scenarios for these kinds of virtual hosting ? Name Based - typical tomcat virtual hosting, one HOME instance with many contexts, each as an individual host IP based / port based - multiple instances of tomcat ( how is it with performance and memory consuption?) running on IP aliases (virtual IPs) for one network adapter, usually behind http apache server that can run name based virtual hostings. Otherwise I can't figure out how would I forward requests in iptables/firewall based on IP address, which is just one. How is IP based virtual hosting done as to Tomcat and multiple instances ? I'd like to hear some usage scenarios from your experience. How are you running your applications. Cause there are applications having it's own modified classloader and they are developed in a way to run alone withing a tomcat instance. Then there are trivial applications which can run within one instance without problems. Many thanks

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• StackOverflowException in c# when no local variable in the function

  - by dnkulkarni

  when i do this static void Main() { Main(); } I receive stackoverflow exception. As i have read so far about C# they say ONLY local variable of value types (and short living ones) will go on stack. But here in the code there are no local variable to go on stack then what overflows it ? I know from assembly code line Perspective that reference to Main() will go on stack too ? Is that right ?

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• A very basic auto-expanding list/array

  - by MainMa

  Hi, I have a method which returns an array of fixed type objects (let's say MyObject). The method creates a new empty Stack<MyObject>. Then, it does some work and pushes some number of MyObjects to the end of the Stack. Finally, it returns the Stack.ToArray(). It does not change already added items or their properties, nor remove them. The number of elements to add will cost performance. There is no need to sort/order the elements. Is Stack a best thing to use? Or must I switch to Collection or List to ensure better performance and/or lower memory cost?

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• setting up/installing/configuring nginx LEMP stack on fresh VPS server

  - by grant tailor

  I need some help in settingup/installing and configuring nginx LEMP stack on a fresh new VPS i have. The specs of the CentOS 5.7 VPS are 2GB DDR3 ECC RAM(4GB burst), 1 core 1.5Ghz(3Ghz burst) and 100GB RAID 10 storage, unmetered bandwidth @ 100Mpbs all for a whopping $25/month(unbeatable, yeah i know :) Anyways i have followed this LEMP(will also need MySQL and PHP) stack guide on linode http://library.linode.com/lemp-guides/centos-5 but basically what i want is to be able to host multiple website on this webserver after everything is setup. I am used to using DirectAdmin control panel on other server and want to have things setup so i can host multiple websites...mostly wordpress and drupal themes. Lets say 10 websites on this nginx web server. So can someone please help me on what i need to do to take "full" advantage of nginx power and performance, while been able to easily manage these multiple websites (wordpress and drupal themes)? Thanks.

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• Stack trace in website project, when debug = false

  - by chandmk

  We have a website project. We are logging unhanded exceptions via a appdomain level exception handler. When we set debug= true in web.config, the exception log is showing the offending line numbers in the stack trace. But when we set debug = false, in web.config, log is not displaying the line numbers. We are not in a position to convert the website project in to webapplication project type at this time. Its legacy application and almost all the code is in aspx pages. We also need to leave the project in 'updatable' mode. i.e. We can't user pre-compile option. We are generating pdb files. Is there anyway to tell this kind of website projects to generate the pdb files, and show the line numbers in the stack trace?

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• the difference between Max Heap and sorted stack

  - by matin1234

  Hi I want to know that when we can sort a stack with a Collections.sort method so why we need a new data structure like max heap?thanks

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• OutOfMemoryException, stack size is huge, large number of threads

  - by Captain Comic

  Hello, I was profiling my .net windows service. I was trying to discover OutOfMemoryException and discovered that my stack size is huge and is growing because the the number of threads keeps growing. Each thread gets 1024 KB on Windows x64 machine. Thus when my app has 754 threads the stack size would be 772 MB. The problem for me is that i don't know where these thread come from. Initially my app has a very limited number of threads and they keep growing with time. I have two suspicions - either these threads are created by WCF or by database connection. My application uses both WCF and datasets. Also I tried to profile my app in Ants do Trace i can see large number of System.ServiceModel.Channels.ClientReliableDuplexSessionChannel and this number is increasing with time. I can see thousands of these objects created. So what I want to know is who is creating threads (tools to discover, profilers) and if it is WCF who is creating these threads.

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