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  • My kernel only works in block (0,0)

    - by ZeroDivide
    I am trying to write a simple matrixMultiplication application that multiplies two square matrices using CUDA. I am having a problem where my kernel is only computing correctly in block (0,0) of the grid. This is my invocation code: dim3 dimBlock(4,4,1); dim3 dimGrid(4,4,1); //Launch the kernel; MatrixMulKernel<<<dimGrid,dimBlock>>>(Md,Nd,Pd,Width); This is my Kernel function __global__ void MatrixMulKernel(int* Md, int* Nd, int* Pd, int Width) { const int tx = threadIdx.x; const int ty = threadIdx.y; const int bx = blockIdx.x; const int by = blockIdx.y; const int row = (by * blockDim.y + ty); const int col = (bx * blockDim.x + tx); //Pvalue stores the Pd element that is computed by the thread int Pvalue = 0; for (int k = 0; k < Width; k++) { Pvalue += Md[row * Width + k] * Nd[k * Width + col]; } __syncthreads(); //Write the matrix to device memory each thread writes one element Pd[row * Width + col] = Pvalue; } I think the problem may have something to do with memory but I'm a bit lost. What should I do to make this code work across several blocks?

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  • UIImageView and UIScrollView load lot of pictures

    - by Allan.Chen
    In my app, i use UIImageView and UIScrollView to show lot of pictures(Every time there are about 20 pictures and every pictures about 600px*500px and size is about 600KB ), i use for this code to do this function. Here is code: //Here is pictures Data; self.klpArry = self.pictureData; CGSize size = self.klpScrollView1.frame.size; for (int i=0; i < [klpArr count]; i++) { UIImageView *iv = [[UIImageView alloc] initWithFrame:CGRectMake((size.width * i)+300, 20, 546, 546)]; NSString *filePath = [[NSBundle mainBundle] pathForResource:[klpArr objectAtIndex:i] ofType:@"jpg"]; UIImage *imageData = [[UIImage alloc]initWithData:[NSData dataWithContentsOfFile:filePath]]; [iv setImage:imageData]; iv.backgroundColor = [UIColor grayColor]; [self.klpScrollView1 addSubview:iv]; imageData = nil; iv = nil; iv.image = nil; filePath = nil; [imageData release]; [filePath release]; [iv release]; } // show the picture in scrollview; [self.klpScrollView1 setContentSize:CGSizeMake(size.width * numImage, size.height)]; self.klpScrollView1.pagingEnabled = YES; self.klpScrollView1.showsHorizontalScrollIndicator = NO; self.klpScrollView1.backgroundColor = [UIColor grayColor]; But everytime i init this function, the memory will increase about 5MB, Actually i release UIImageView, UIimage and UIScrollView (vi.image=nil,[vi release]) but i doesn't work, it can't release the memory. BTW, i use my friend code first vi.image=nil then vi=nil; but the pictures not to show on scrollview. any one can help me ?? Thx ~~

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  • Speed/expensive of SQLite query vs. List.contains() for "in-set" icon on list rows

    - by kpdvx
    An application I'm developing requires that the app main a local list of things, let's say books, in a local "library." Users can access their local library of books and search for books using a remote web service. The app will be aware of other users of the app through this web service, and users can browse other users' lists of books in their library. Each book is identified by a unique bookId (represented as an int). When viewing books returned through a search result or when viewing another user's book library, the individual list row cells need to visually represent if the book is in the user's local library or not. A user can have at most 5,000 books in the library, stored in SQLite on the device (and synchronized with the remote web service). My question is, to determine if the book shown in the list row is in the user's library, would it be better to directly ask SQLite (via SELECT COUNT(*)...) or to maintain, in-memory, a List or int[] array of some sort containing the unique bookIds. So, on each row display do I query SQLite or check if the List or int[] array contains the unique bookId? Because the user can have at most 5,000 books, each bookId occupies 4 bytes so at most this would use ~ 20kB. In thinking about this, and in typing this out, it seems obvious to me that it would be far better for performance if I maintained a list or int[] array of in-library bookIds vs. querying SQLite (the only caveat to maintaining an int[] array is that if books are added or removed I'll need to grow or shrink the array by hand, so with this option I'll most likely use an ArrayList or Vector, though I'm not sure of the additional memory overhead of using Integer objects as opposed to primitives). Opinions, thoughts, suggestions?

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  • NVelocity (or Velocity) as a stand-alone formula evaluator

    - by dana
    I am using NVelocity in my application to generate html emails. My application has an event-driven model, where saving and/or updating of objects causes these emails to be sent out. Each event can trigger zero, one or multiple multiple emails. I want to be able to configure which emails get sent out at run-time without having to modify code. I was thinking I could leverage the NVelocity #if() directive to do this. Here is my idea... Step 1) Prior to email sending, the administrator must configure a formula for NVelocity to evaluate. For example: $User.FirstName == "Jack" Step 2) When an object is saved or created, build an NVelocity template in memory based on the input formula. For example: String formula = GetFormulaFromDB(); // $User.FirstName == "Jack" String templ = "#if( " + formula + ") 1 #else 0 #end"; Step 3) Execute the NVelocity engine in memory against the template. Check the results to see if we have to send the email: String result = VelocityMerge(templ); // utility function if( result.Trim() == "1" ) { SendEmail(); } I know this is not exactly what NVelocity was intended to do, but I think it just might work :) One of the benefits of doing things this way is that the same syntax can be used for the formula as is used inside the template. Does anybody have any words of caution or suggestions? Is there a way to execute the #if() directive without jumping through hoops like I have above? Is there a recommended way to validate the formula syntax ahead of time? Thanks.

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  • Android: How to do this framing paint?

    - by iDroid Explorer
    I Have Some static images like below: Now, I want is, when i touch on the face or hand, then the selected color should be fill on that skin portion. See below image of result: So how to get the result like above ?? Redo and Undo Functionality Should be also there. I have try with the FloodFill color but doing that i can only able to do color in to the perticular portion. as FloodFill only fill the color till the same pixwl color comes. If the touch place pixel color get change the it will not fill color on it. So Usinf FloodFill i got the result like below image, If i press on the hand, then only hand portion will fill with color, instead of it i want to fill color to the other hand and face also. So Please help me in this case. EDITED After some reply i got the solution like this one. But still there is a memory issue. It consume lots of memory to draw the color. So please can anyone help me for it ?

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  • Error while sending image through ajax to WCF

    - by Samar Rizvi
    Here is my form: <form id="register" enctype="multipart/form-data"> <input type="text" name="first_name" placeholder="First Name" id="first_name" /> <input type="text" name="last_name" placeholder="Last Name" id="last_name" /> <input type="text" name="input_email" placeholder="Confirm your email" id="input_email" class="loginEmail" /> <input type="password" name="input_password" placeholder="Password" id="input_password" class="loginPassword" /> <input type="password" name="repeat_password" placeholder="Repeat password" id="repeat_password" class="loginPassword" /> <input type="file" name="image_file" id="image_file" /> <div class="logControl"> <div class="memory"></div> <input type="submit" name="submit" value="Register" class="buttonM bBlue" id="register_submit"/> <div class="clear"></div> </div> <p><h3>Or click <a href="login.html">here</a> to login</h3></p> </form> Here is jquery call that I make: function WCFJSON() { $(".memory").html('<img src="images/elements/loaders/7s.gif" />'); Data = new FormData($('form')[0]); $.ajax({ type: 'POST', //GET or POST or PUT or DELETE verb url: "WCFService/Service.svc/Register", // Location of the service data: Data, //Data sent to server async:false, cache:false, contentType: false, // content type sent to server dataType: DataType, //Expected data format from server processdata: false, //True or False success: function(msg) {//On Successfull service call ... }, error: ...// When Service call fails }); } $(document).ready(function(){ $("#register").submit(function(){ $('#input_password').val(CryptoJS.MD5($('#input_password').val())); $('#repeat_password').val(CryptoJS.MD5($('#repeat_password').val())); WCFJSON(); return false; }); }); Now when I submit the form , page refreshes with get elements in the url. But if I remove the file input from the form, jquery works fine.

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  • How do i prevent my code from being stolen?

    - by Calmarius
    What happens exactly when I launch a .NET exe? I know that C# is compiled to IL code and I think the generated exe file just a launcher that starts the runtime and passes the IL code to it. But how? And how complex process is it? IL code is embedded in the exe. I think it can be executed from the memory without writing it to the disk while ordinary exe's are not (ok, yes but it is very complicated). My final aim is extracting the IL code and write my own encrypted launcher to prevent scriptkiddies to open my code in Reflector and just steal all my classes easily. Well I can't prevent reverse engineering completely. If they are able to inspect the memory and catch the moment when I'm passing the pure IL to the runtime then it won't matter if it is a .net exe or not, is it? I know there are several obfuscator tools but I don't want to mess up the IL code itself. EDIT: so it seems it isn't worth trying what I wanted. They will crack it anyway... So I will look for an obfuscation tool. And yes my friends said too that it is enough to rename all symbols to a meaningless name. And reverse engineering won't be so easy after all.

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  • Access array of c-structs using Python ctypes

    - by sadris
    I have a C-function that allocates memory at the address passed to and is accessed via Python. The pointer contents does contain an array of structs in the C code, but I am unable to get ctypes to access the array properly beyond the 0th element. How can I get the proper memory offset to be able to access the non-zero elements? Python's ctypes.memset is complaining about TypeErrors if I try to use their ctypes.memset function. typedef struct td_Group { unsigned int group_id; char groupname[256]; char date_created[32]; char date_modified[32]; unsigned int user_modified; unsigned int user_created; } Group; int getGroups(LIBmanager * handler, Group ** unallocatedPointer); ############# python code below: class Group(Structure): _fields_ = [("group_id", c_uint), ("groupname", c_char*256), ("date_created", c_char*32), ("date_modified", c_char*32), ("user_modified", c_uint), ("user_created", c_uint)] myGroups = c_void_p() count = libnativetest.getGroups( nativePointer, byref(myGroups) ) casted = cast( myGroups, POINTER(Group*count) ) for x in range(0,count): theGroup = cast( casted[x], POINTER(Group) ) # this only works for the first entry in the array: print "~~~~~~~~~~" + theGroup.contents.groupname Related: Access c_char_p_Array_256 in Python using ctypes

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  • Web services or shared database for (game) server communication?

    - by jaaronfarr
    We have 2 server clusters: the first is made up of typical web applications backed by SQL databases. The second are highly optimized multiplayer game servers which keep all data in memory. Both clusters communicate with clients via HTTP (Ajax with JSON). There are a few cases in which we need to share data between the two server types, for example, reporting back and storing the results of a game (should ultimately end up in the database). We're considering several approaches for inter-server communication: Just share the MySQL databases between clusters (introduce SQL to the game servers) Sharing data in a distributed key-value store like Memcache, Redis, etc. Use an RPC technology like Google ProtoBufs or Apache Thrift Using RESTful web services (the game server would POST back to the web servers, for example) At the moment, we're leaning towards web services or just sharing the database. Sharing the database seems easy, but we're concerned this adds extra memory and a new dependency into the game servers. Web services provide good separation of concerns and fit with the existing Ajax we use, but add complexity, overhead and many more ways for communication to fail. Are there any other good reasons not to use one or the other approach? Which would be easier to scale?

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  • Algorithm to determine if array contains n...n+m?

    - by Kyle Cronin
    I saw this question on Reddit, and there were no positive solutions presented, and I thought it would be a perfect question to ask here. This was in a thread about interview questions: Write a method that takes an int array of size m, and returns (True/False) if the array consists of the numbers n...n+m-1, all numbers in that range and only numbers in that range. The array is not guaranteed to be sorted. (For instance, {2,3,4} would return true. {1,3,1} would return false, {1,2,4} would return false. The problem I had with this one is that my interviewer kept asking me to optimize (faster O(n), less memory, etc), to the point where he claimed you could do it in one pass of the array using a constant amount of memory. Never figured that one out. Along with your solutions please indicate if they assume that the array contains unique items. Also indicate if your solution assumes the sequence starts at 1. (I've modified the question slightly to allow cases where it goes 2, 3, 4...) edit: I am now of the opinion that there does not exist a linear in time and constant in space algorithm that handles duplicates. Can anyone verify this? The duplicate problem boils down to testing to see if the array contains duplicates in O(n) time, O(1) space. If this can be done you can simply test first and if there are no duplicates run the algorithms posted. So can you test for dupes in O(n) time O(1) space?

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  • Does Monitor.Wait ensure that fields are re-read?

    - by Marc Gravell
    It is generally accepted (I believe!) that a lock will force any values from fields to be reloaded (essentially acting as a memory-barrier or fence - my terminology in this area gets a bit loose, I'm afraid), with the consequence that fields that are only ever accessed inside a lock do not themselves need to be volatile. (If I'm wrong already, just say!) A good comment was raised here, questioning whether the same is true if code does a Wait() - i.e. once it has been Pulse()d, will it reload fields from memory, or could they be in a register (etc). Or more simply: does the field need to be volatile to ensure that the current value is obtained when resuming after a Wait()? Looking at reflector, Wait calls down into ObjWait, which is managed internalcall (the same as Enter). The scenario in question was: bool closing; public bool TryDequeue(out T value) { lock (queue) { // arbitrary lock-object (a private readonly ref-type) while (queue.Count == 0) { if (closing) { // <==== (2) access field here value = default(T); return false; } Monitor.Wait(queue); // <==== (1) waits here } ...blah do something with the head of the queue } } Obviously I could just make it volatile, or I could move this out so that I exit and re-enter the Monitor every time it gets pulsed, but I'm intrigued to know if either is necessary.

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  • Copy object using pointer (templates)

    - by Azodious
    How the push_back of stl::vector is implemented so it can make copy of any datatype .. may be pointer, double pointer and so on ... I'm implementing a template class having a function push_back almost similar to vector. Within this method a copy of argument should be inserted in internal memory allocated memory. but the argument is a pointer. (an object pointer). Can you pls tell how to create copy from pointer. so that if i delete the pointer in caller still the copy exists in my template class? Code base is as follows: template<typename T> class Vector { public: void push_back(const T& val_in) { T* a = *(new T(val_in)); m_pData[SIZE++] = a; } } Caller: Vector<MyClass*> v(3); MyClass* a = new MyClass(); a->a = 0; a->b = .5; v.push_back(a); delete a; Thanks.

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  • Why does reusing arrays increase performance so significantly in c#?

    - by Willem
    In my code, I perform a large number of tasks, each requiring a large array of memory to temporarily store data. I have about 500 tasks. At the beginning of each task, I allocate memory for an array : double[] tempDoubleArray = new double[M]; M is a large number depending on the precise task, typically around 2000000. Now, I do some complex calculations to fill the array, and in the end I use the array to determine the result of this task. After that, the tempDoubleArray goes out of scope. Profiling reveals that the calls to construct the arrays are time consuming. So, I decide to try and reuse the array, by making it static and reusing it. It requires some additional juggling to figure out the minimum size of the array, requiring an extra pass through all tasks, but it works. Now, the program is much faster (from 80 sec to 22 sec for execution of all tasks). double[] tempDoubleArray = staticDoubleArray; However, I'm a bit in the dark of why precisely this works so well. Id say that in the original code, when the tempDoubleArray goes out of scope, it can be collected, so allocating a new array should not be that hard right? I ask this because understanding why it works might help me figuring out other ways to achieve the same effect, and because I would like to know in what cases allocation gives performance issues.

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  • Android designing an app to keep me logged into a wifi access point

    - by MrGibbage
    At the gym where I work out, they have an open wifi access point. The way it is set up, once you "connect", you have to navigate to a web page (it is a 1.1.X.X ip address) and click the "I agree" button, after presumably reading the user agreement. The problem is, they have it set up to log you out once an hour, which always happens in the middle of my workout. I have the SSID remembered, so it connects automatically when I come in range, but I get an android notification that further action is needed to fully connect. What I was wondering is if there a work around so that I don't have to click-through every hour? I was thinking of writing an app that could detect when I was in range, or when "half-connected", and then have it somehow complete the registration process. Perhaps this will have to be done by loading the web page in memory and then somehow clicking the "I agree" button. What I would like help with is: 1) what is the terminology involved here? What state is the connection in when I am connected, but I haven't clicked through? What other connection states may apply? If I knew that, I might just be able to research this and come up with a solution. Are these different states "detectable"? It seems like it is since I get a notification that I need to complete the registration process when I am "half-connected". 2) I know there are plugins for desktop browsers that can click buttons (like the keepass plugins, which will log you into a site). How could I replicate this in Android? Ideally I would like to do it internally, in memory, rather than firing up a browser. Possible? Comments? Is my understanding and thought process sound here, or am I overlooking something?

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  • Receiving "expected expression before" Error When Using A Struct

    - by Zach Dziura
    I'm in the process of creating a simple 2D game engine in C with a group of friends at school. I'd like to write this engine in an Object-Oriented way, using structs as classes, function pointers as methods, etc. To emulate standard OOP syntax, I created a create() function which allocates space in memory for the object. I'm in the process of testing it out, and I'm receiving an error. Here is my code for two files that I'm using to test: test.c: #include <stdio.h> int main() { typedef struct { int i; } Class; Class *test = (Class*) create(Class); test->i = 1; printf("The value of \"test\" is: %i\n", test->i); return 0; } utils.c: #include <stdio.h> #include <stdlib.h> #include "utils.h" void* create(const void* class) { void *obj = (void*) malloc(sizeof(class)); if (obj == 0) { printf("Error allocating memory.\n"); return (int*) -1; } else { return obj; } } void destroy(void* object) { free(object); } The utils.h file simply holds prototypes for the create() and destroy() functions. When I execute gcc test.c utils.c -o test, I'm receiving this error message: test.c: In function 'main': test.c:10:32: error: expected expression before 'Class' I know it has something to do with my typedef at the beginning, and how I'm probably not using proper syntax. But I have no idea what that proper syntax is. Can anyone help?

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  • JavaScript array random index insertion and deletion

    - by Tomi
    I'm inserting some items into array with randomly created indexes, for example like this: var myArray = new Array(); myArray[123] = "foo"; myArray[456] = "bar"; myArray[789] = "baz"; ... In other words array indexes do not start with zero and there will be "numeric gaps" between them. My questions are: Will these numeric gaps be somehow allocated (and therefore take some memory) even when they do not have assigned values? When I delete myArray[456] from upper example, would items below this item be relocated? EDIT: Regarding my question/concern about relocation of items after insertion/deletion - I want to know what happens with the memory and not indexes. More information from wikipedia article: Linked lists have several advantages over dynamic arrays. Insertion of an element at a specific point of a list is a constant-time operation, whereas insertion in a dynamic array at random locations will require moving half of the elements on average, and all the elements in the worst case. While one can "delete" an element from an array in constant time by somehow marking its slot as "vacant", this causes fragmentation that impedes the performance of iteration.

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  • When is a Web Service constructor called? [Java Netbeans 6.7.1 & Tomcat 6.0.18]

    - by Shaitan00
    I am migrating a Java RMI application to Java Web Service (school assignment) and I've encountered an issue... Currently my Java Server creates an instance of the Remote Object, this object has a constructor and takes a parameter (int ID) which tells it which database to load in memory - works like a charm ... Now, migrating this to Web Services is causing my a problem - first I needed to add a default constructor because it wouldn't deploy without it, and then while doing some reading all these discussions about "stateless web services" kept coming up ... For example, if I "start" my webservice with parameter(0) it would load from Databse 0 and all requests from Clients would be done using that data... I want this to only happen when I start the WebService and NOT everytime the client connects... Loading from the DB is expensive and takes time, so I want to do it once so that clients when they connect just deal with the data in memory ... This is how it works with my Java RMI .... but can this also work with Web Services? Any advice would be much appreciated. Thanks,

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  • What could the negative effects be of attaching to a process as a debugger?

    - by I_like_traffic_lights
    Background A client of mine has a major problem. They have a CRM system, which was created by a single person over a period of 9 years. Unfortunatelly, a few weeks ago, this person died. I believe the company has learned their lesson, and they have started a project of rewriting the CRM system to a modern platform. I have been hired to create a solution in the meantime to make adaptations to the CRM system. I have given up understanding the code, as this would take too long. My solution, is therefore, to make a window and show this on top of the CRM system, whenever this CRM system is showing. This part works fine, but my major problem is extracting the data from the CRM system. Proposed solution After excluding 6 approaches, including runtime code injection, memory searching, database integration, I have arrived at attaching to the process as a debugger, so I get notified about event, and use this in combination with reading from process memory. This approach seems to work, but I am worried about possible side-effects of this approach. Question What are the dangers of using this in a production environment, where there are 250 employees utilizing the system. Needless to say, I cannot risk reducing the already shaky stability of the system.

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  • Sorting a very large text file in Java

    - by Alice
    Hi, I have a large text file I need to sort in Java. The format is: word [tab] frequency [new line] The algorithm for sorting is: Read some of the file, filtering for purlely alphabetic words. Once you have X number of alphabetic words, call Collections.sort and write the result to a file. Repeat until you have finished reading the file. Start reading two sorted files, comparing line by line for the word with higher frequency, and writing at the same time to a new file as to not load much into your memory Repeat until all files are merged into one large file Right now I've divided the large file into smaller ones (sorted by descending frequency) with 10,000 lines each. I know I need to somehow merge these files back together, but I'm not sure how to go about this. I've created a LinkedList to keep track of all the files created. The algorithm says to compare each line in the two files, except I've tried a case where , say file1 = 8,6,5,3,1 and file2 = 9,8,8,8,8. Then if I compare them line by line I would get file3 = 9,8,8,6,8,5,8,3,8,1 which is incorrectly sorted (they should be in decreasing order). I think I'm misunderstanding some part of the algorithm. If someone could point out what I should do instead, I'd greatly appreciate it. Thanks. edit: Yes this is an assignment. We aren't allowed to increase memory unfortunately :(

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  • Delete on a very deep tree

    - by Kathoz
    I am building a suffix trie (unfortunately, no time to properly implement a suffix tree) for a 10 character set. The strings I wish to parse are going to be rather long (up to 1M characters). The tree is constructed without any problems, however, I run into some when I try to free the memory after being done with it. In particularly, if I set up my constructor and destructor to be as such (where CNode.child is a pointer to an array of 10 pointers to other CNodes, and count is a simple unsigned int): CNode::CNode(){ count = 0; child = new CNode* [10]; memset(child, 0, sizeof(CNode*) * 10); } CNode::~CNode(){ for (int i=0; i<10; i++) delete child[i]; } I get a stack overflow when trying to delete the root node. I might be wrong, but I am fairly certain that this is due to too many destructor calls (each destructor calls up to 10 other destructors). I know this is suboptimal both space, and time-wise, however, this is supposed to be a quick-and-dirty solution to a the repeated substring problem. tl;dr: how would one go about freeing the memory occupied by a very deep tree? Thank you for your time.

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  • Is a web-server (e.g servlets) a good solution for an IM server?

    - by John
    I'm looking at a new app, broadly speaking an IM application with a strong client-server model - all communications go through a server so they can be logged centrally. The server will be Java in some form, clients could at this point be anything from a .NET Desktop app to Flex/Silverlight, to a simple web-interface using JS/AJAX. I had anticipated doing the server using standard J2EE so I get a thread-safe, multi-user server for 'free'... to make things simple let's say using Servlets (but in practice SpringMVC would be likely). This all seemed very neat but I'm concerned if the stateless nature of Servlets is the best approach. If my memory of servlets (been a year or two) is right, each time a client sent a HTTP request, typically a new message entered by the user, the servlet could not assume it had the user/chat in memory and might have to get it from the DB... regardless it has to look it up. Then it either has to use some PUSH system to inform other members of the chat, or cache that there are new messages, for other clients who poll the server using AJAX or similar - and when they poll it again has to lookup the chat, including new messages, and send the new data. I'm wondering if a better system would be the server is running core Java, and implements a socket-based communication with clients. This allows much more immediate data transfer and is more flexible if say the IM client included some game you could play. But then you're writing a custom server and sockets don't sound very friendly to a browser-based client on current browsers. Am I missing some big piece of the puzzle here, it kind of feels like I am? Perhaps a better way to ask the question would simply be "if the client was browser-based using HTML/JS and had to run on IE7+,FF2+ (i.e no HTML5), how would you implement the server?" edit: if you are going to suggest using XMPP, I have been trying to get my head around this in another question, so please consider if that's a more appropriate place to discuss this specifically.

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  • Java: multi-threaded maps: how do the implementations compare?

    - by user346629
    I'm looking for a good hash map implementation. Specifically, one that's good for creating a large number of maps, most of them small. So memory is an issue. It should be thread-safe (though losing the odd put might be an OK compromise in return for better performance), and fast for both get and put. And I'd also like the moon on a stick, please, with a side-order of justice. The options I know are: HashMap. Disastrously un-thread safe. ConcurrentHashMap. My first choice, but this has a hefty memory footprint - about 2k per instance. Collections.sychronizedMap(HashMap). That's working OK for me, but I'm sure there must be faster alternatives. Trove or Colt - I think neither of these are thread-safe, but perhaps the code could be adapted to be thread safe. Any others? Any advice on what beats what when? Any really good new hash map algorithms that Java could use an implementation of? Thanks in advance for your input!

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  • Objective-C Result from a Static Method saved to class instance variable giving "EXC_BAD_ACCESS" when used.

    - by KinGBin
    I am trying to store the md5 string as a class instance variable instead of the actual password. I have a static function that will return a md5 string which I'm trying to store in an instance variable instead of the actual password. I have the following setter for my class instance variable: -(void)setPassword:(NSString *)newpass{ if(newpass != password){ password = [utils md5HexDigest:newpass]; } } This will pass back the correct md5 string and save it to the password variable in my init function: [self setPassword:pword];. If I call another instance method and try to access self.password" I will get "EXC_BAD_ACCESS". I understand that the memory is getting released, but I have no clue to make sure it stays. I have tried alloc init with autorelease with no luck. This is the md5HexDigest function getting called during the init (graciously found in another stackoverflow question): + (NSString*)md5HexDigest:(NSString*)input { const char* str = [input UTF8String]; unsigned char result[CC_MD5_DIGEST_LENGTH]; CC_MD5(str, strlen(str), result); NSMutableString *ret = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH*2]; for(int i = 0; i<CC_MD5_DIGEST_LENGTH; i++) { [ret appendFormat:@"%02x",result[i]]; } return ret; } Any help/pointers would be greatly appreciated. I would rather have the md5 string saved in memory than the actual password calling the md5 every time I needed to use the password. Thanks in advance.

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  • How do I read hex numbers into an unsigned int in C [Solved]

    - by sil3nt
    I'm wanting to read hex numbers from a text file into an unsigned integer so that I can execute Machine instructions. It's just a simulation type thing that looks inside the text file and according to the values and its corresponding instruction outputs the new values in the registers. For example, the instructions would be: 1RXY - Save register R with value in memory address XY 2RXY - Save register R with value XY BRXY - Jump to register R if xy is this and that etc.. ARXY - AND register R with value at memory address XY The text file contains something like this each in a new line. (in hexidecimal) 120F B007 290B My problem is copying each individual instruction into an unsigned integer...how do I do this? #include <stdio.h> int main(){ FILE *f; unsigned int num[80]; f=fopen("values.txt","r"); if (f==NULL){ printf("file doesnt exist?!"); } int i=0; while (fscanf(f,"%x",num[i]) != EOF){ fscanf(f,"%x",num[i]); i++; } fclose(f); printf("%x",num[0]); }

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  • How to iteratively generate k elements subsets from a set of size n in java?

    - by Bea Metitiri
    Hi, I'm working on a puzzle that involves analyzing all size k subsets and figuring out which one is optimal. I wrote a solution that works when the number of subsets is small, but it runs out of memory for larger problems. Now I'm trying to translate an iterative function written in python to java so that I can analyze each subset as it's created and get only the value that represents how optimized it is and not the entire set so that I won't run out of memory. Here is what I have so far and it doesn't seem to finish even for very small problems: public static LinkedList<LinkedList<Integer>> getSets(int k, LinkedList<Integer> set) { int N = set.size(); int maxsets = nCr(N, k); LinkedList<LinkedList<Integer>> toRet = new LinkedList<LinkedList<Integer>>(); int remains, thresh; LinkedList<Integer> newset; for (int i=0; i<maxsets; i++) { remains = k; newset = new LinkedList<Integer>(); for (int val=1; val<=N; val++) { if (remains==0) break; thresh = nCr(N-val, remains-1); if (i < thresh) { newset.add(set.get(val-1)); remains --; } else { i -= thresh; } } toRet.add(newset); } return toRet; } Can anybody help me debug this function or suggest another algorithm for iteratively generating size k subsets? EDIT: I finally got this function working, I had to create a new variable that was the same as i to do the i and thresh comparison because python handles for loop indexes differently.

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