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  • How can I improve the performance of LinqToSql queries that use EntitySet properties?

    - by DanM
    I'm using LinqToSql to query a small, simple SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of what makes LinqToSql so appealing. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance besides resorting to doing all the joins manually? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view. Update Here are the table definitions for the example I used in my question: create table Order ( Id int identity(1, 1) primary key, ProductName ntext null ) create table Customer ( Id int identity(1, 1) primary key, OrderId int null references Order (Id) )

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  • Ember Data Sycn - LocalStorage+REST+RealTime+Online/Offline

    - by Miguel Madero
    We have a combination of requirements in terms o data access. Pre-load some reference data. We need reference data to survive browser restarts instead of just living in memory to avoid loading it all the time. I'm currently using the LocalStorageAdapter for that. Once we have it, we would like to sync changes (polling or using Socket.IO in the background and updating the LocalStorage could do the trick) There're other models that are more transactional, where we would need to directly go to the Server and get/save them. It would be nice to use something like the RESTAdapter for that. Lastly, there're some operations that should work off-line and changes should be synced later. To make it more concrete: * We pre-load vendor and "favorite products" into Local Storage. We work offline with those. * We need to sync server changes to vendor and product information. * If they search the full catalog, that requires them to be online. * When offline, we need to allow users to add something to their cart or even submit and order. We would like to queue this action and submit it when they have an Internet Connection. So a few questions are derived from this: * Is there a way to user RESTAdapter in combination with LocalStorage? * Is there some Socket.IO support? (Happy to do this part manually) * Is there Queueing support? Ideally at the Ember-Data level. I know we will have to do a lot of this manually and pull together the different lego pieces, but I wanted to ask for some perspective from experience Ember devs.

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  • Which MySQL Fork/Version to Pick??

    - by Drew
    As most of you know, Sun acquired MySQL (and later Oracle acquired Sun), and during these acquisitions, there were a lot of FUD in MySQL community which resulted in creation of various forks. Today we have MySQL from MySQL, Percona (XtraDB) MySQL, OurDelta MySQL, MariaDB, Drizzle to name a few. Which brings us to the source of the problem. We are in the process of upgrading our databases (hardware/software) and I would like to know which one of the forks should I go with. Each has their own set of pros/cons. We are currently using MySQL 5.0.x from MySQL/Linux on an 8-core machine. Our new hardware is a monster with 32 cores and 32GB of memory connecting to a fast NetApp Storage via FC. I would like to stick with MySQL from MySQL but I have heard horror stories on how badly MySQL 5.1 performs on many cores. I have also heard that MySQL 5.4 performs better on multi-core machines but that's still not production ready. In addition, I have also heard a lot of good things about Percona builds. This is what I know so far: MySQL 5.1 from MySQL: Reliable choice, but doesn't scale well on a big machine Percona: Scales well, good backing company. I don't have much experience with it MariaDB: Don't know much about it besides that it was founded by Original MySQL developers (including Monty) OurDelta: Don't know much Drizzle: Mostly optimized for cloud computing I would like to know what's the general notion about this problem. Which build/version should I go with? How are you guys picking your builds/versions? Thanks!

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  • Creating subtree from tree which is represented in xml - python

    - by Jay
    Hi I have an XML (in the form of tree), I require to create sub-tree out of it. For ex: <a> <b> <c>Hello</c> <d> <e>Hi</e> </a> Subtree would be <root> <a> <b> <c>Hello</c> </b> </a> <a> <d> <e>Hi</e> </d> </a> </root> What is the best XML library in python to do it? Any algorithm that already does this would also be helpful. Note: the XML doc won't be that big, it will easily fit in memory.

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  • A generic error occurred in GDI+, JPEG Image to MemoryStream

    - by madcapnmckay
    Hi, This seems to be a bit of an infamous error all over the web. So much so that I have been unable to find an answer to my problem as my scenario doesn't fit. An exception gets thrown when I save the image to the stream. Weirdly this works perfectly with a png but gives the above error with jpg and gif which is rather confusing. Most similar problem out there relate to saving images to files without permissions. Ironically the solution is to use a memory stream as I am doing.... public static byte[] ConvertImageToByteArray(Image imageToConvert) { using (var ms = new MemoryStream()) { ImageFormat format; switch (imageToConvert.MimeType()) { case "image/png": format = ImageFormat.Png; break; case "image/gif": format = ImageFormat.Gif; break; default: format = ImageFormat.Jpeg; break; } imageToConvert.Save(ms, format); return ms.ToArray(); } } More detail to the exception. The reason this causes so many issues is the lack of explanation :( System.Runtime.InteropServices.ExternalException was unhandled by user code Message="A generic error occurred in GDI+." Source="System.Drawing" ErrorCode=-2147467259 StackTrace: at System.Drawing.Image.Save(Stream stream, ImageCodecInfo encoder, EncoderParameters encoderParams) at System.Drawing.Image.Save(Stream stream, ImageFormat format) at Caldoo.Infrastructure.PhotoEditor.ConvertImageToByteArray(Image imageToConvert) in C:\Users\Ian\SVN\Caldoo\Caldoo.Coordinator\PhotoEditor.cs:line 139 at Caldoo.Web.Controllers.PictureController.Croppable() in C:\Users\Ian\SVN\Caldoo\Caldoo.Web\Controllers\PictureController.cs:line 132 at lambda_method(ExecutionScope , ControllerBase , Object[] ) at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClassa.<InvokeActionMethodWithFilters>b__7() at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) InnerException: OK things I have tried so far. Cloning the image and working on that. Retrieving the encoder for that MIME passing that with jpeg quality setting. Please can anyone help.

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  • NES Programming - Nametables?

    - by Jeffrey Kern
    Hello everyone, I'm wondering about how the NES displays its graphical muscle. I've researched stuff online and read through it, but I'm wondering about one last thing: Nametables. Basically, from what I've read, each 8x8 block in a NES nametable points to a location in the pattern table, which holds graphic memory. In addition, the nametable also has an attribute table which sets a certain color palette for each 16x16 block. They're linked up together like this: (assuming 16 8x8 blocks) Nametable, with A B C D = pointers to sprite data: ABBB CDCC DDDD DDDD Attribute table, with 1 2 3 = pointers to color palette data, with < referencing value to the left, ^ above, and ' to the left and above: 1<2< ^'^' 3<3< ^'^' So, in the example above, the blocks would be colored as so 1A 1B 2B 2B 1C 1D 2C 2C 3D 3D 3D 3D 3D 3D 3D 3D Now, if I have this on a fixed screen - it works great! Because the NES resolution is 256x240 pixels. Now, how do these tables get adjusted for scrolling? Because Nametable 0 can scroll into Nametable 1, and if you keep scrolling Nametable 0 will wrap around again. That I get. But what I don't get is how to scroll the attribute table wraps around as well. From what I've read online, the 16x16 blocks it assigns attributes for will cause color distortions on the edge tiles of the screen (as seen when you scroll left to right and vice-versa in SMB3). The concern I have is that I understand how to scroll the nametables, but how do you scroll the attribute table? For intsance, if I have a green block on the left side of the screen, moving the screen to right should in theory cause the tiles to the right to be green as well until they move more into frame, to which they'll revert to their normal colors.

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  • After Delete Trigger Fires Only After Delete?

    - by Brandi
    I thought "after delete" meant that the trigger is not fired until after the delete has already taken place, but here is my situation... I made 3, nearly identical SQL CLR after delete triggers in C#, which worked beautifully for about a month. Suddenly, one of the three stopped working while an automated delete tool was run on it. By stopped working, I mean, records could not be deleted from the table via client software. Disabling the trigger caused deletes to be allowed, but re-enabling it interfered with the ability to delete. So my question is 'how can this be the case?' Is it possible the tool used on it futzed up the memory? It seems like even if the trigger threw an exception, if it is AFTER delete, shouldn't the records be gone? All the trigger looks like is this: ALTER TRIGGER [sysdba].[AccountTrigger] ON [sysdba].[ACCOUNT] AFTER DELETE AS EXTERNAL NAME [SQL_IO].[SQL_IO.WriteFunctions].[AccountTrigger] GO The CLR trigger does one select and one insert into another database. I don't yet know if there are any errors from SQL Server Mgmt Studio, but will update the question after I find out.

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  • mysterical error

    - by Görkem Buzcu
    i get "customer_service_simulator.exe stopped" error, but i dont know why? this is my c programming project and i have limited time left before deadline. the code is: #include <stdio.h> #include <stdlib.h> #include<time.h> #define FALSE 0 #define TRUE 1 /*A Node declaration to store a value, pointer to the next node and a priority value*/ struct Node { int priority; //arrival time int val; //type int wait_time; int departure_time; struct Node *next; }; Queue Record that will store the following: size: total number of elements stored in the list front: it shows the front node of the queue (front of the queue) rear: it shows the rare node of the queue (rear of the queue) availability: availabity of the teller struct QueueRecord { struct Node *front; struct Node *rear; int size; int availability; }; typedef struct Node *niyazi; typedef struct QueueRecord *Queue; Queue CreateQueue(int); void MakeEmptyQueue(Queue); void enqueue(Queue, int, int); int QueueSize(Queue); int FrontOfQueue(Queue); int RearOfQueue(Queue); niyazi dequeue(Queue); int IsFullQueue(Queue); int IsEmptyQueue(Queue); void DisplayQueue(Queue); void sorteddequeue(Queue); void sortedenqueue(Queue, int, int); void tellerzfunctionz(Queue *, Queue, int, int); int main() { int system_clock=0; Queue waitqueue; int exit, val, priority, customers, tellers, avg_serv_time, sim_time,counter; char command; waitqueue = CreateQueue(0); srand(time(NULL)); fflush(stdin); printf("Enter number of customers, number of tellers, average service time, simulation time\n:"); scanf("%d%c %d%c %d%c %d",&customers, &command,&tellers,&command,&avg_serv_time,&command,&sim_time); fflush(stdin); Queue tellerarray[tellers]; for(counter=0;counter<tellers;counter++){ tellerarray[counter]=CreateQueue(0); //burada teller sayisi kadar queue yaratiyorum } for(counter=0;counter<customers;counter++){ priority=1+(int)rand()%sim_time; //this will generate the arrival time sortedenqueue(waitqueue,1,priority); //here i put the customers in the waiting queue } tellerzfunctionz(tellerarray,waitqueue,tellers,customers); DisplayQueue(waitqueue); DisplayQueue(tellerarray[0]); DisplayQueue(tellerarray[1]); // waitqueue-> printf("\n\n"); system("PAUSE"); return 0; } /*This function initialises the queue*/ Queue CreateQueue(int maxElements) { Queue q; q = (struct QueueRecord *) malloc(sizeof(struct QueueRecord)); if (q == NULL) printf("Out of memory space\n"); else MakeEmptyQueue(q); return q; } /*This function sets the queue size to 0, and creates a dummy element and sets the front and rear point to this dummy element*/ void MakeEmptyQueue(Queue q) { q->size = 0; q->availability=0; q->front = (struct Node *) malloc(sizeof(struct Node)); if (q->front == NULL) printf("Out of memory space\n"); else{ q->front->next = NULL; q->rear = q->front; } } /*Shows if the queue is empty*/ int IsEmptyQueue(Queue q) { return (q->size == 0); } /*Returns the queue size*/ int QueueSize(Queue q) { return (q->size); } /*Shows the queue is full or not*/ int IsFullQueue(Queue q) { return FALSE; } /*Returns the value stored in the front of the queue*/ int FrontOfQueue(Queue q) { if (!IsEmptyQueue(q)) return q->front->next->val; else { printf("The queue is empty\n"); return -1; } } /*Returns the value stored in the rear of the queue*/ int RearOfQueue(Queue q) { if (!IsEmptyQueue(q)) return q->rear->val; else { printf("The queue is empty\n"); return -1; } } /*Displays the content of the queue*/ void DisplayQueue(Queue q) { struct Node *pos; pos=q->front->next; printf("Queue content:\n"); printf("-->Priority Value\n"); while (pos != NULL) { printf("--> %d\t %d\n", pos->priority, pos->val); pos = pos->next; } } void enqueue(Queue q, int element, int priority){ if(IsFullQueue(q)){ printf("Error queue is full"); } else{ q->rear->next=(struct Node *)malloc(sizeof(struct Node)); q->rear=q->rear->next; q->rear->next=NULL; q->rear->val=element; q->rear->priority=priority; q->size++; } } void sortedenqueue(Queue q, int val, int priority) { struct Node *insert,*temp; insert=(struct Node *)malloc(sizeof(struct Node)); insert->val=val; insert->priority=priority; temp=q->front; if(q->size==0){ enqueue(q, val, priority); } else{ while(temp->next!=NULL && temp->next->priority<insert->priority){ temp=temp->next; } //printf("%d",temp->priority); insert->next=temp->next; temp->next=insert; q->size++; if(insert->next==NULL){ q->rear=insert; } } } niyazi dequeue(Queue q) { niyazi del; niyazi deli; del=(niyazi)malloc(sizeof(struct Node)); deli=(niyazi)malloc(sizeof(struct Node)); if(IsEmptyQueue(q)){ printf("Queue is empty!"); return NULL; } else { del=q->front->next; q->front->next=del->next; deli->val=del->val; deli->priority=del->priority; free(del); q->size--; return deli; } } void sorteddequeue(Queue q) { struct Node *temp; struct Node *min; temp=q->front->next; min=q->front; int i; for(i=1;i<q->size;i++) { if(temp->next->priority<min->next->priority) { min=temp; } temp=temp->next; } temp=min->next; min->next=min->next->next; free(temp); if(min->next==NULL){ q->rear=min; } q->size--; } void tellerzfunctionz(Queue *a, Queue b, int c, int d){ int i; int value=0; int priority; niyazi temp; temp=(niyazi)malloc(sizeof(struct Node)); if(c==1){ for(i=0;i<d;i++){ temp=dequeue(b); sortedenqueue((*(a)),temp->val,temp->priority); } } else{ for(i=0;i<d;i++){ while(b->front->next->val==1){ if((*(a+value))->availability==1){ temp=dequeue(b); sortedenqueue((*(a+value)),temp->val,temp->priority); (*(a+value))->rear->val=2; } else{ value++; } } } } } //end of the program

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  • How do you organise multiple git repositories?

    - by dbr
    With SVN, I had a single big repository I kept on a server, and checked-out on a few machines. This was a pretty good backup system, and allowed me easily work on any of the machines. I could checkout a specific project, commit and it updated the 'master' project, or I could checkout the entire thing. Now, I have a bunch of git repositories, for various projects, several of which are on github. I also have the SVN repository I mentioned, imported via the git-svn command.. Basically, I like having all my code (not just projects, but random snippets and scripts, some things like my CV, articles I've written, websites I've made and so on) in one big repository I can easily clone onto remote machines, or memory-sticks/harddrives as backup. The problem is, since it's a private repository, and git doesn't allow checking out of a specific folder (that I could push to github as a separate project, but have the changes appear in both the master-repo, and the sub-repos) I could use the git submodule system, but it doesn't act how I want it too (submodules are pointers to other repositories, and don't really contain the actual code, so it's useless for backup) Currently I have a folder of git-repos (for example, ~/code_projects/proj1/.git/ ~/code_projects/proj2/.git/), and after doing changes to proj1 I do git push github, then I copy the files into ~/Documents/code/python/projects/proj1/ and do a single commit (instead of the numerous ones in the individual repos). Then do git push backupdrive1, git push mymemorystick etc So, the question: How do your personal code and projects with git repositories, and keep them synced and backed-up?

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  • Web Audio API and mobile browsers

    - by Michael
    I've run into a problem while implementing sound and music into an HTML game that I'm building. I'm using the Web Audio API, loading all the sound files with XMLHttpRequests and decoding them into an AudioBufferSourceNode with AudioContext.prototype.decodeAudioData(). It looks something like this: var request = new XMLHttpRequest(); request.open("GET", "soundfile.ogg", true); request.responseType = "arraybuffer"; request.onload = function() { context.decodeAudioData(request.response) } request.send(); Everything plays fine, but on mobile the decodeAudioData takes an absurdly long time for the background music. I then tried using AudioContext.prototype.createMediaElementSource() to load the music from an HTML Audio object, since they support streaming and don't have to load the whole file into memory at once. It looked something like this: var audio = new Audio('soundfile.ogg'); var source = context.createMediaElementSource(audio); var mainVolume = context.createGain(); source.connect(mainVolume); mainVolume.connect(context.destination); This loads much faster, but the audio volume isn't affected by the gain node. Works fine on desktop, so I'm assuming this is a bug/limitation of mobile Chrome (testing on Android). Is there actually no good, well-performing way to handle sound on mobile browsers or am just I doing something stupid?

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  • Does The Clear Method On A Collection Release The Event Subscriptions?

    - by DaveB
    I have a collection private ObservableCollection<Contact> _contacts; In the constructor of my class I create it _contacts = new ObservableCollection<Contact>(); I have methods to add and remove items from my collection. I want to track changes to the entities in my collection which implement the IPropertyChanged interface so I subscribe to their PropertyChanged event. public void AddContact(Contact contact) { ((INotifyPropertyChanged)contact).PropertyChanged += new PropertyChangedEventHandler(Contact_PropertyChanged); _contacts.Add(contact); } public void AddContact(int index, Contact contact) { ((INotifyPropertyChanged)contact).PropertyChanged += new PropertyChangedEventHandler(Contact_PropertyChanged); _contacts.Insert(index, contact); } When I remove an entity from the collection, I unsubscribe from the PropertyChanged event. I am told this is to allow the entity to be garbage collected and not create memory issues. public void RemoveContact(Contact contact) { ((INotifyPropertyChanged)contact).PropertyChanged -= Contact_PropertyChanged; _contacts.Remove(contact); } So, I hope this is all good. Now, I need to clear the collection in one of my methods. My first thought would be to call _contacts.Clear(). Then I got to wondering if this releases those event subscriptions? Would I need to create my own clear method? Something like this: public void ClearContacts() { foreach(Contact contact in _contacts) { this.RemoveContact(contact); } } I am hoping one of the .NET C# experts here could clear this up for me or tell me what I am doing wrong.

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  • Why does multiple sessions started on the same page gets the same session id?

    - by Calmarius
    I tryed the following: <?php session_name('user'); session_start(); // sets an 'user' cookie with session id. // This session stores the user's login data. // Its an ordinary session. $USERSESSION=$_SESSION; // saving this session $userSessId=session_id(); session_write_close(); //closing this session session_name('chatroom'); session_start(); // set a 'chatroom' cookie but contains the same session id and points to the same data :( . // This session would be used to store the chat text. This session would be // shared between all users joined in this chat room by setting the same session id for all members. // by calling session_regenerate_id would make a diffent session id for every user and it won't be a chat room anymore. ?> So I want to do a chat like thing with sessions. On the client side it would be done with ajax that polls this php page in every 5-10 seconds. Sessions may be cached in the server's memory so it can be accessible fast. I can store the chat in the database but my service runs on a free webhost which is limited, only 4 mysql connections allowed at a time which is almost nothing. I try to touch my database as least times as possible.

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  • char[] and char* compatibility?

    - by Aerovistae
    In essence, will this code work? And before you say "Run it and see!", I just realized my cygwin didn't come with gcc and it's currently 40 minutes away from completing reinstallation. That being said: char* words[1000]; for(int i = 0; i<1000; i++) words[i] = NULL; char buffer[ 1024 ]; //omit code that places "ADD splash\0" into the buffer if(strncmp (buffer, "ADD ", 4){ char* temp = buffer + 4; printf("Adding: %s", temp); int i = 0; while(words[i] != NULL) i++; words[i] = temp; } I'm mostly uncertain about the line char* temp = buffer + 4, and also whether I can assign words[i] in the manner that I am. Am I going to get type errors when I eventually try to compile this in 40 minutes? Also-- if this works, why don't I need to use malloc() on each element of words[]? Why can I say words[i] = temp, instead of needing to allocate memory for words[i] the length of temp?

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  • Do all C compilers allow functions to return structures?

    - by Jordan S
    I am working on a program in C and using the SDCC compiler for a 8051 architecture device. I am trying to write a function called GetName that will read 8 characters from Flash Memory and return the character array in some form. I know that it is not possible to return an array in C so I am trying to do it using a struct like this: //********************FLASH.h file******************************* MyStruct GetName(int i); //Function prototype #define NAME_SIZE 8 typedef struct { char Name[NAME_SIZE]; } MyStruct; extern MyStruct GetName(int i); // *****************FLASH.c file*********************************** #include "FLASH.h" MyStruct GetName( int i) { MyStruct newNameStruct; //... // Fill the array by reading data from Flash //... return newNameStruct; } I don't have any references to this function yet but for some reason, I get a compiler error that says "Function cannot return aggregate." Does this mean that my compiler does not support functions that return structs? Or am I just doing something wrong?

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  • How do the operators < and > work with pointers?

    - by Øystein
    Just for fun, I had a std::list of const char*, each element pointing to a null-terminated text string, and ran a std::list::sort() on it. As it happens, it sort of (no pun intended) did not sort the strings. Considering that it was working on pointers, that makes sense. According to the documentation of std::list::sort(), it (by default) uses the operator < between the elements to compare. Forgetting about the list for a moment, my actual question is: How do these (, <, =, <=) operators work on pointers in C++ and C? Do they simply compare the actual memory addresses? char* p1 = (char*) 0xDAB0BC47; char* p2 = (char*) 0xBABEC475; e.g. on a 32-bit, little-endian system, p1 p2 because 0xDAB0BC47 0xBABEC475? Testing seems to confirm this, but I thought it'd be good to put it on StackOverflow for future reference. C and C++ both do some weird things to pointers, so you never really know...

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  • CUDA - multiple kernels to compute a single value

    - by Roger
    Hey, I'm trying to write a kernel to essentially do the following in C float sum = 0.0; for(int i = 0; i < N; i++){ sum += valueArray[i]*valueArray[i]; } sum += sum / N; At the moment I have this inside my kernel, but it is not giving correct values. int i0 = blockIdx.x * blockDim.x + threadIdx.x; for(int i=i0; i<N; i += blockDim.x*gridDim.x){ *d_sum += d_valueArray[i]*d_valueArray[i]; } *d_sum= __fdividef(*d_sum, N); The code used to call the kernel is kernelName<<<64,128>>>(N, d_valueArray, d_sum); cudaMemcpy(&sum, d_sum, sizeof(float) , cudaMemcpyDeviceToHost); I think that each kernel is calculating a partial sum, but the final divide statement is not taking into account the accumulated value from each of the threads. Every kernel is producing it's own final value for d_sum? Does anyone know how could I go about doing this in an efficient way? Maybe using shared memory between threads? I'm very new to GPU programming. Cheers

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  • How to get the size of a binary tree ?

    - by Andrei Ciobanu
    I have a very simple binary tree structure, something like: struct nmbintree_s { unsigned int size; int (*cmp)(const void *e1, const void *e2); void (*destructor)(void *data); nmbintree_node *root; }; struct nmbintree_node_s { void *data; struct nmbintree_node_s *right; struct nmbintree_node_s *left; }; Sometimes i need to extract a 'tree' from another and i need to get the size to the 'extracted tree' in order to update the size of the initial 'tree' . I was thinking on two approaches: 1) Using a recursive function, something like: unsigned int nmbintree_size(struct nmbintree_node* node) { if (node==NULL) { return(0); } return( nmbintree_size(node->left) + nmbintree_size(node->right) + 1 ); } 2) A preorder / inorder / postorder traversal done in an iterative way (using stack / queue) + counting the nodes. What approach do you think is more 'memory failure proof' / performant ? Any other suggestions / tips ? NOTE: I am probably going to use this implementation in the future for small projects of mine. So I don't want to unexpectedly fail :).

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  • PHP file upload issue

    - by Varun
    I am working on a PHP based, ticket management system. While creating a ticket, one can upload an attachment. I want to put a limit (say 10 MB) per file upload. To implement this I plan the following- 1. In php.ini set post_max_size = 10M 2.In PHP script which receives the POST- Since the file is larger than post_max_size, $_FILES[] will be empty. But I can still check the content-length header and discard the upload, if size more than 10M. While testing this I tried uploading a file of 1 GB and analysed the http traffic and this is what I found. - the entire 1 GB data is first uploaded to a to the server temporarily and discarded once the http request completes. Though I couldn't exactly find out where the file was getting saved(as it was not there in the temporary directory in the server.), but my http traffic analyzer showed that the browser did send 1 GB data to the server. - the PHP script execution started only after completion of the http request(i.e after uploading the entire 1 GB) Now I have 2 concerns: a) People may exploit my server bandwidth by trying to upload large file, which I will have to discard anyways. b) Even worse, if someone starts uploading a huge file (say 100 GB), entire 100 GB data is first uploaded to the server temporarily, that means for that period, it will consume that much of memory on my server. What's the common solution for this. Am I missing something here?

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  • Is C++ (one of) the best language to learn at first

    - by AlexV
    C++ is one of the most used programming language in the world since like 25+ years. My first job as programmer was in C++ and I coded in C++ everyday for nearly 4 years. Now I do mostly PHP, but I will forever cherish this C++ background. C++ has helped me understand many "under the hood" features/behaviors/restrictions of many other (and different) programming languages like PHP and Delphi. I'm a full time programmer for 6+ years now and since I have a quite varied programming background I often get questions by "newbies" as where to start to become a "good" programmer. I think C++ is one of the best language to start with because it gives you a real usefull experience that will last and will teach you how things work under the hood. It's not the easier one to learn for a newbie, but in my opinion it's one that will reward in the long term. I would like to know your opinion on this matter to add to my arguments when I guide "newbies". After this introduction, here's my question : Is C++ (one of) the best language to learn at first for you. Since it's subjective, I've marked this question as community wiki. EDIT: This question is not about why Java (or C# or any other language) is better than C++ to start with, it's about what's make C++ a good choice or not a good choice to learn as one of your firsts languages. For example, for me C++ made me understand how the memory works. Now today in many languages everything is managed by the garbadge collector and some people don't even know that. I'm glad I know how it works underneath and I think it can help you to write better code.

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  • XML Decryption Bug (referencing issue)

    - by OrangePekoe
    Hi, Needing some explanation of what exactly the decryption is doing, in addition to some help on solving the problem. Currently, when a portion of XML is encrypted, and then decrypted, the DOM appears to work correctly. We can see the element is encrypted and then see it return back once it is decrypted. Our problem lies when a user tries to change data in that same element after decryption has occurred. When a user changes some settings, data in the XML should change. However, if the user attempts to change an XML element that has been decrypted the changes are not reflected in the DOM. We have a reference pointer to the XML element that is used to bind the element to an object. If you encrypt the node and then decrypt it, the reference pointer now points to a valid orphaned XML element that is no longer part of the DOM. After decryption, there will be 2 copies of the XML element. One in the DOM as expected (though will not reflect new changes), and one orphaned element in memory that is still referenced by our pointer. The orphaned element is valid (reflects new changes). We can see that this orphaned element is owned by the DOM, but when we try to return its parent, it returns null. The question is: Where did this orphaned xml element come from? And how can we get it to correctly append (replace old data) to the DOM? The code resembles: public static void Decrypt(XmlDocument Doc, SymmetricAlgorithm Alg) { if (Doc == null) throw new ArgumentNullException("Doc"); if (Alg == null) throw new ArgumentNullException("Alg"); XmlElement encryptedElement = Doc.GetElementsByTagName("EncryptedData")[0] as XmlElement; if (encryptedElement == null) { throw new XmlException("The EncryptedData element was not found."); } EncryptedData edElement = new EncryptedData(); edElement.LoadXml(encryptedElement); EncryptedXml exml = new EncryptedXml(); byte[] rgbOutput = exml.DecryptData(edElement, Alg); exml.ReplaceData(encryptedElement, rgbOutput); }

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  • Multi-reader IPC solution?

    - by gct
    I'm working on a framework in C++ (just for fun for now), that lets the user write plugins that use a standard API to stream data between each other. There's going to be three basic transport mechanisms for the data: files, sockets, and some kind of IPC piping system. The system is set up so that for the non-file transport, each stream can have multiple readers. IE once a server socket it setup, multiple computers can connect and stream the data. I'm a little stuck at the multi-reader IPC system though. All my plugins run in threads so they live in the same address space, so some kind of shared memory system would work fine, I was thinking I'd write my own circular buffer with a write pointer and read pointers chassing it around the buffer, but I have my doubts that I can achieve the same performance as something like linux pipes. I'm curious what people would suggest for a multi-reader solution to something like this? Is the overhead for pipes or domain sockets low enough that I could just open a connection to each reader and issue separate writes to each reader? This is intended to be significant volumes of data (tens of mega-samples/sec), so performance is a must.

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  • Howto use predicates in LINQ to Entities for Entity Framework objects

    - by user274947
    I'm using LINQ to Entities for Entity Framework objects in my Data Access Layer. My goal is to filter as much as I can from the database, without applying filtering logic on in-memory results. For that purpose Business Logic Layer passes a predicate to Data Access Layer. I mean Func<MyEntity, bool> So, if I use this predicate directly, like public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.Where(x => isMatched(x)); } I'm getting the exception [System.NotSupportedException] --- {"The LINQ expression node type 'Invoke' is not supported in LINQ to Entities."} Solution in that question suggests to use AsExpandable() method from LINQKit library. But again, using public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.AsExpandable().Where(x => isMatched(x)); } I'm getting the exception Unable to cast object of type 'System.Linq.Expressions.FieldExpression' to type 'System.Linq.Expressions.LambdaExpression' Is there way to use predicate in LINQ to Entities query for Entity Framework objects, so that it is correctly transformed it into a SQL statement. Thank you.

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  • User to kernel mode big picture?

    - by fsdfa
    I've to implement a char device, a LKM. I know some basics about OS, but I feel I don't have the big picture. In a C programm, when I call a syscall what I think it happens is that the CPU is changed to ring0, then goes to the syscall vector and jumps to a kernel memmory space function that handle it. (I think that it does int 0x80 and in eax is the offset of the syscall vector, not sure). Then, I'm in the syscall itself, but I guess that for the kernel is the same process that was before, only that it is in kernel mode, I mean the current PCB is the process that called the syscall. So far... so good?, correct me if something is wrong. Others questions... how can I write/read in process memory?. If in the syscall handler I refer to address, say, 0xbfffffff. What it means that address? physical one? Some virtual kernel one?

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  • What's the best way to transfer a large dataset over a .NET web service?

    - by Malvineous
    I've inherited a C# .NET application which talks to a web service, and the web service talks to an Oracle database. I need to add an export function to the UI, to produce an Excel spreadsheet of some of the data. I have created a web service function to run a database query, load the data into a DataTable and then return it, which works fine for a small number of rows. However there is enough data in the full run that the client application locks up for a few minutes and then returns a timeout error. Obviously this isn't the best way to retrieve such a large dataset. Before I go ahead and come up with some dodgy way of splitting the call, I'm wondering if there is already something in place that can handle this. At the moment I'm thinking of a startExport function then repeatedly calling a next50Rows function until there is no data left, but because web services are stateless this means I'm going to have to keep some sort of ID number around and deal with the associated permissions. It would mean that I don't have to load the entire data set into the web server's memory though, which is one good thing. So if anyone knows a better way to retrieve a large amount of data (in a table format) over a .NET web service, please let me know!

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  • Objective C code to handle large amount of data processing in iPhone

    - by user167662
    I had the following code that takes in 14 mb or more of image data encoded in base4 string and converts them to jpeg before writing to a file in iphone. It crashes my program giving the following error : Program received signal: “0”. warning: check_safe_call: could not restore current frame I tweak my program and it can process a few more images before the error appear again. My coding is as follows: // parameters is an array where the fourth element contains a list of images in base64 >encoded string NSMutableArray *imageStrList = (NSMutableArray*) [parameters objectAtIndex:5]; while (imageStrList.count != 0) { NSString *imgString = [imageStrList objectAtIndex:0]; // Create a file name using my own Utility class NSString *fileName = [Utility generateFileNName]; NSData *restoredImg = [NSData decodeWebSafeBase64ForString:imgString]; UIImage *img = [UIImage imageWithData: restoredImg]; NSData *imgJPEG = UIImageJPEGRepresentation(img, 0.4f); [imgJPEG writeToFile:fileName atomically:YES]; [imageStrList removeObjectAtIndex:0]; } I tried playing around with UIImageJPEGRepresentation and found out that the lower the value, the more image it can processed but this should not be the way. I am wondering if there is anyway to free up memory of the imageStrList immediately after processing each image so that it can be used by the next one in the line.

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