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  • Using pthread to perform matrix multiplication

    - by shadyabhi
    I have both matrices containing only ones and each array has 500 rows and columns. So, the resulting matrix should be a matrix of all elements having value 500. But, I am getting res_mat[0][0]=5000. Even other elements are also 5000. Why? #include<stdio.h> #include<pthread.h> #include<unistd.h> #include<stdlib.h> #define ROWS 500 #define COLUMNS 500 #define N_THREADS 10 int mat1[ROWS][COLUMNS],mat2[ROWS][COLUMNS],res_mat[ROWS][COLUMNS]; void *mult_thread(void *t) { /*This function calculates 50 ROWS of the matrix*/ int starting_row; starting_row = *((int *)t); starting_row = 50 * starting_row; int i,j,k; for (i = starting_row;i<starting_row+50;i++) for (j=0;j<COLUMNS;j++) for (k=0;k<ROWS;k++) res_mat[i][j] += (mat1[i][k] * mat2[k][j]); return; } void fill_matrix(int mat[ROWS][COLUMNS]) { int i,j; for(i=0;i<ROWS;i++) for(j=0;j<COLUMNS;j++) mat[i][j] = 1; } int main() { int n_threads = 10; //10 threads created bcos we have 500 rows and one thread calculates 50 rows int j=0; pthread_t p[n_threads]; fill_matrix(mat1); fill_matrix(mat2); for (j=0;j<10;j++) pthread_create(&p[j],NULL,mult_thread,&j); for (j=0;j<10;j++) pthread_join(p[j],NULL); printf("%d\n",res_mat[0][0]); return 0; }

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  • [Perl] Testing for EAGAIN / EWOULDBLOCK on a recv

    - by Robert S. Barnes
    I'm testing a socket to see if it's still open: my $dummy = ''; my $ret = recv($sock, $dummy, 1, MSG_DONTWAIT | MSG_PEEK); if (!defined $ret || (length($dummy) == 0 && $! != EAGAIN && $! != EWOULDBLOCK )) { logerr("Broken pipe? ".__LINE__." $!"); } else { # socket still connected, reuse logerr(__LINE__.": $!"); return $sock; } I'm passing this code a socket I know for certain is open and it's always going through the first branch and logging "Broken pipe? 149 Resource temporarily unavailable". I don't understand how this is happening since "Resource temporarily unavailable" is supposed to correspond to EAGAIN as far as I know. I'm sure there must be something simple I'm missing. And yes, I know this is not a full proof way to test and I account for that.

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  • pagesize and its ratio to 4096

    - by osgx
    Hello Are there systems, where minimal page of memory (pagesize) has a size not divisible by 2, or by 1024, 4096? Can it be 3000 or 3500? Will any posix program break, if pagesize will be not divisible by 1024?

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  • Using TTMessageController with Multiple Data Sources

    - by PF1
    Hi Everyone: I am wondering if there is some way to set a separate .datasource for each custom field in a TTMessageController. Right now I am using a TTMessageController subclass (and referencing the data source controller delegate) and simply setting the data source of the message controller to self. But I only believe this will work for one field with one set of options. Thanks for any help!

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  • Broadcast-style Bluetooth using Sockets on the iPhone?

    - by Kyle
    Is there any way to open a broadcast bluetooth socket, take a listen and send replies? I want a proper peer to peer system where I broadcast and listen for broadcasts in an area. That way, variable clients can mingle. Is this possible? My theory is this: If GameKit can sit around wasting 25 seconds of the users time whilst having access to a broadcast socket, can't I? Or, must I be in kernel mode for such access? I'm not really sure where the proper bluetooth headers are as well. Thanks for reading!

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  • Sending multiline message via sockets without closing the connection

    - by Yasir Arsanukaev
    Hello folks. Currently I have this code of my client-side Haskell application: import Network.Socket import Network.BSD import System.IO hiding (hPutStr, hPutStrLn, hGetLine, hGetContents) import System.IO.UTF8 connectserver :: HostName -- ^ Remote hostname, or localhost -> String -- ^ Port number or name -> IO Handle connectserver hostname port = withSocketsDo $ do -- withSocketsDo is required on Windows -- Look up the hostname and port. Either raises an exception -- or returns a nonempty list. First element in that list -- is supposed to be the best option. addrinfos <- getAddrInfo Nothing (Just hostname) (Just port) let serveraddr = head addrinfos -- Establish a socket for communication sock <- socket (addrFamily serveraddr) Stream defaultProtocol -- Mark the socket for keep-alive handling since it may be idle -- for long periods of time setSocketOption sock KeepAlive 1 -- Connect to server connect sock (addrAddress serveraddr) -- Make a Handle out of it for convenience h <- socketToHandle sock ReadWriteMode -- Were going to set buffering to LineBuffering and then -- explicitly call hFlush after each message, below, so that -- messages get logged immediately hSetBuffering h LineBuffering return h sendid :: Handle -> String -> IO String sendid h id = do hPutStr h id -- Make sure that we send data immediately hFlush h -- Retrieve results hGetLine h The code portions in connectserver are from this chapter of Real World Haskell book where they say: When dealing with TCP data, it's often convenient to convert a socket into a Haskell Handle. We do so here, and explicitly set the buffering – an important point for TCP communication. Next, we set up lazy reading from the socket's Handle. For each incoming line, we pass it to handle. After there is no more data – because the remote end has closed the socket – we output a message about that. Since hGetContents blocks until the server closes the socket on the other side, I used hGetLine instead. It satisfied me before I decided to implement multiline output to client. I wouldn't like the server to close a socket every time it finishes sending multiline text. The only simple idea I have at the moment is to count the number of linefeeds and stop reading lines after two subsequent linefeeds. Do you have any better suggestions? Thanks.

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  • What benefits does IOC provide over soft-coding?

    - by dotnetdev
    Take the following article for example: http://weblogs.asp.net/psteele/archive/2009/11/23/use-dependency-injection-to-simplify-application-settings.aspx?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+dotnetmvp+%28Patrick+Steele%27s+.NET+Blog%29 I don't see what benefit there is from the IOC approach as opposed to the traditional soft-coding approach. Can someone tell me what I am missing? Thanks

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  • Testing bash scripts

    - by nimcap
    We have a system that has some bash scripts running besides Java code. Since we are trying to "Test Everything That Could Possibly Break" and those bash scripts may break, we want to test them. The problem is it is hard to test the scripts. Is there a way or a best practice to test bash scripts? Or should we quit using bash scripts and look for alternative solutions that are testable?

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  • How do I profile in DrScheme?

    - by kunjaan
    How Do I profile my functions using DrScheme? (require profile) (define (factorial n) (cond ((= n 1) 1) (else (* n (factorial (- n 1)))))) (profile factorial) The above code returns Profiling results ----------------- Total cpu time observed: 0ms (out of 0ms) Number of samples taken: 0 (once every 0ms) ==================================== Caller Idx Total Self Name+srcLocal% ms(pct) ms(pct) Callee ==================================== > I tried: - (profile (factorial 100)) - (profile factorial) (factorial 100) But it gives me the same result. What am I doing wrong?

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  • Tricking a Unix Commandline Program into Accepting a File Stream

    - by Alan Storm
    Hypothetical situation. I have a command line program in *nix (linux, BSD, etc.). It was written so that you pass it a text file as an argument $ program file.txt Run the program, it looks at the text in file.txt. Is it possible to "trick" this program into accepting input from a file stream rather than reading a file via disk? I'm pretty comfortable using unix pipes to do stuff, but there's still something a little mysterious about their internals that make it so I can't say (definitively) yes or not to the above question.

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  • linux firewall in c

    - by asha
    i m implementing a firewall for linux,i want to block packets using loadable kernal module(lkm). please help me how can i do it ? i just know that it can be done by lkm by using some function in it,like init(),clean_up. i want to know how to use DROP,ACCEPT in blocking function within lkm. i want to do it without iptable command.

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  • State Monad, why not a tuple?

    - by thr
    I've just wrapped my head around monads (at least I'd like to think I have) and more specifically the state monad, which some people that are way smarter then me figured out, so I'm probably way of with this question. Anyway, the state monad is usually implemented with a M<'a as something like this (F#): type State<'a, 'state> = State of ('state -> 'a * 'state) Now my question: Is there any reason why you couldn't use a tuple here? Other then the possible ambiguity between MonadA<'a, 'b> and MonadB<'a, 'b> which would both become the equivalent ('a * 'b) tuple. Edit: Added example for clarity type StateMonad() = member m.Return a = (fun s -> a, s) member m.Bind(x, f) = (fun s -> let a, s_ = x s in f a s_) let state = new StateMonad() let getState = (fun s -> s, s) let setState s = (fun _ -> (), s) let execute m s = m s |> fst

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  • How well do zippers perform in practice, and when should they be used?

    - by Rob
    I think that the zipper is a beautiful idea; it elegantly provides a way to walk a list or tree and make what appear to be local updates in a functional way. Asymptotically, the costs appear to be reasonable. But traversing the data structure requires memory allocation at each iteration, where a normal list or tree traversal is just pointer chasing. This seems expensive (please correct me if I am wrong). Are the costs prohibitive? And what under what circumstances would it be reasonable to use a zipper?

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  • Efficient algorithm to generate all solutions of a linear diophantine equation with ai=1

    - by Ben
    I am trying to generate all the solutions for the following equations for a given H. With H=4 : 1) ALL solutions for x_1 + x_2 + x_3 + x_4 =4 2) ALL solutions for x_1 + x_2 + x_3 = 4 3) ALL solutions for x_1 + x_2 = 4 4) ALL solutions for x_1 =4 For my problem, there are always 4 equations to solve (independently from the others). There are a total of 2^(H-1) solutions. For the previous one, here are the solutions : 1) 1 1 1 1 2) 1 1 2 and 1 2 1 and 2 1 1 3) 1 3 and 3 1 and 2 2 4) 4 Here is an R algorithm which solve the problem. library(gtools) H<-4 solutions<-NULL for(i in seq(H)) { res<-permutations(H-i+1,i,repeats.allowed=T) resum<-apply(res,1,sum) id<-which(resum==H) print(paste("solutions with ",i," variables",sep="")) print(res[id,]) } However, this algorithm makes more calculations than needed. I am sure it is possible to go faster. By that, I mean not generating the permutations for which the sums is H Any idea of a better algorithm for a given H ?

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  • Naming Suggestions For A Function Providing Method Chaining In A Different Way

    - by sid3k
    I've coded an experimental function which makes passed objects chainable by using high order functions. It's name is "chain" for now, and here is a usage example; chain("Hello World") (print) // evaluates print function by passing "Hello World" object. (console.log,"Optional","Parameters") (returnfrom) // returns "Hello World" It looks lispy but behaves very different since it's coded in a C based language, I don't know if there is a name for this idiom and I couldn't any name more suitable than "chain". Any ideas, suggestions?

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  • How Search Engine Bots Crawl Forums?

    - by Waleed Eissa
    If I have a forums site with a large number of threads, will the search engine bot crawl the whole site every time? Say I have over 1,000,000 threads in my site, will they get crawled every time the bot crawls my site? or how does it work? I want my website to be indexed but I don't want the bot to kill my website! In other words I don't want the bot to keep crawling the old threads again and again every time it crawls my website. Also, what about the pages crawled before? Will the bot request them every time it crawls my website to make sure they are still on the site? I'm asking this because I only link to the latest threads, i.e. there's a page that contains a list of all the latest threads, but I don't link to the older threads, they have to be explicitly requested by URL, e.g. http://www.mysite.com/showthread.aspx?threadid=7 , will this work to stop the bot from bringing my site down and consuming all my bandwidth? P.S. The site is still under development but I want to know in order to design the site so that search engine bots don't bring it down. Thanks

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  • How do programmers work together on a project?

    - by Laith J
    Hello, I've always programmed alone, I'm still a student so I never programmed with anyone else, I haven't even used a version control system before. I'm working on a project now that requires knowledge of how programmers work together on a piece of software in a company. How is the software compiled? Is it from the version control system? Is it by individual programmers? Is it periodic? Is it when someone decides to build or something? Are there any tests that are done to make sure it "works"? Anything will do. Thanks.

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  • getting started with lex

    - by cambr
    I need to format some hexdump like this: 00010: 02 03 04 05 00020: 02 03 04 08 00030: 02 03 04 08 00010: 02 03 04 05 00020: 02 03 04 05 02 03 04 05 02 03 04 08 to 02 03 04 05 02 03 04 08 02 03 04 02 03 04 05 02 03 04 05 02 03 04 05 02 03 04 a) remove the address fields, if present b) remove any 08 at the end of a paragraph (followed by an empty line) c) remove any empty lines How can this be done using lex? thanks!

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  • Odd performance with C# Asynchronous server socket

    - by The.Anti.9
    I'm working on a web server in C# and I have it running on Asynchronous socket calls. The weird thing is that for some reason, when you start loading pages, the 3rd request is where the browser won't connect. It just keeps saying "Connecting..." and doesn't ever stop. If I hit stop. and then refresh, it will load again, but if I try another time after that it does the thing where it doesn't load again. And it continues in that cycle. I'm not really sure what is making it do that. The code is kind of hacked together from a couple of examples and some old code I had. Any miscellaneous tips would be helpful as well. Heres my little Listener class that handles everything (pastied here. thought it might be easier to read this way) using System; using System.Collections.Generic; using System.Net; using System.Net.Sockets; using System.Text; using System.Threading; namespace irek.Server { public class Listener { private int port; private Socket server; private Byte[] data = new Byte[2048]; static ManualResetEvent allDone = new ManualResetEvent(false); public Listener(int _port) { port = _port; } public void Run() { server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); IPEndPoint iep = new IPEndPoint(IPAddress.Any, port); server.Bind(iep); Console.WriteLine("Server Initialized."); server.Listen(5); Console.WriteLine("Listening..."); while (true) { allDone.Reset(); server.BeginAccept(new AsyncCallback(AcceptCon), server); allDone.WaitOne(); } } private void AcceptCon(IAsyncResult iar) { allDone.Set(); Socket s = (Socket)iar.AsyncState; Socket s2 = s.EndAccept(iar); SocketStateObject state = new SocketStateObject(); state.workSocket = s2; s2.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); } private void Read(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; Socket s = state.workSocket; int read = s.EndReceive(iar); if (read > 0) { state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, read)); if (s.Available > 0) { s.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); return; } } if (state.sb.Length > 1) { string requestString = state.sb.ToString(); // HANDLE REQUEST HERE // Temporary response string resp = "<h1>It Works!</h1>"; string head = "HTTP/1.1 200 OK\r\nContent-Type: text/html;\r\nServer: irek\r\nContent-Length:"+resp.Length+"\r\n\r\n"; byte[] answer = Encoding.ASCII.GetBytes(head+resp); // end temp. state.workSocket.BeginSend(answer, 0, answer.Length, SocketFlags.None, new AsyncCallback(Send), state.workSocket); } } catch (Exception) { return; } } private void Send(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; int sent = state.workSocket.EndSend(iar); state.workSocket.Shutdown(SocketShutdown.Both); state.workSocket.Close(); } catch (Exception) { } return; } } } And my SocketStateObject: public class SocketStateObject { public Socket workSocket = null; public const int BUFFER_SIZE = 1024; public byte[] buffer = new byte[BUFFER_SIZE]; public StringBuilder sb = new StringBuilder(); }

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  • deciding between subprocess, multiprocesser and thread in Python?

    - by user248237
    I'd like to parallelize my Python program so that it can make use of multiple processors on the machine that it runs on. My parallelization is very simple, in that all the parallel "threads" of the program are independent and write their output to separate files. I don't need the threads to exchange information but it is imperative that I know when the threads finish since some steps of my pipeline depend on their output. Portability is important, in that I'd like this to run on any Python version on Mac, Linux and Windows. Given these constraints, which is the most appropriate Python module for implementing this? I am tryign to decide between thread, subprocess and multiprocessing, which all seem to provide related functionality. Any thoughts on this? I'd like the simplest solution that's portable. Thanks.

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