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  • Multi-threaded random_r is slower than single threaded version.

    - by Nixuz
    The following program is essentially the same the one described here. When I run and compile the program using two threads (NTHREADS == 2), I get the following run times: real 0m14.120s user 0m25.570s sys 0m0.050s When it is run with just one thread (NTHREADS == 1), I get run times significantly better even though it is only using one core. real 0m4.705s user 0m4.660s sys 0m0.010s My system is dual core, and I know random_r is thread safe and I am pretty sure it is non-blocking. When the same program is run without random_r and a calculation of cosines and sines is used as a replacement, the dual-threaded version runs in about 1/2 the time as expected. #include <pthread.h> #include <stdlib.h> #include <stdio.h> #define NTHREADS 2 #define PRNG_BUFSZ 8 #define ITERATIONS 1000000000 void* thread_run(void* arg) { int r1, i, totalIterations = ITERATIONS / NTHREADS; for (i = 0; i < totalIterations; i++){ random_r((struct random_data*)arg, &r1); } printf("%i\n", r1); } int main(int argc, char** argv) { struct random_data* rand_states = (struct random_data*)calloc(NTHREADS, sizeof(struct random_data)); char* rand_statebufs = (char*)calloc(NTHREADS, PRNG_BUFSZ); pthread_t* thread_ids; int t = 0; thread_ids = (pthread_t*)calloc(NTHREADS, sizeof(pthread_t)); /* create threads */ for (t = 0; t < NTHREADS; t++) { initstate_r(random(), &rand_statebufs[t], PRNG_BUFSZ, &rand_states[t]); pthread_create(&thread_ids[t], NULL, &thread_run, &rand_states[t]); } for (t = 0; t < NTHREADS; t++) { pthread_join(thread_ids[t], NULL); } free(thread_ids); free(rand_states); free(rand_statebufs); } I am confused why when generating random numbers the two threaded version performs much worse than the single threaded version, considering random_r is meant to be used in multi-threaded applications.

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  • recv receiving not whole data sometime

    - by milo
    hi all, i have following issue: here is the chunk of code: void get_all_buf(int sock, std::string & inStr) { int n = 1; char c; char temp[1024*1024]; bzero(temp, sizeof(temp)); n = recv(sock, temp, sizeof(temp), 0); inStr = temp; }; but sometimes recv returning not whole data (data length always less then sizeof(temp)), only it's part. write side always sends me whole data (i got it with sniffer). what matter? thx. P.S. i know, good manner suggests me to check n (if (n < 0) perror ("error while receiving data), but it doesn't matter now - it's not reason of my problem. P.S.2 i've forgot - it's blocking socket.

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  • Grep for 2 words after pattern found

    - by Dileep Ch
    The scenario is i have a file and contains a string "the date and time is 2012-12-07 17:11:50" I had searched and found a command grep 'the date and time is' 2012-12-07.txt | cut -d\ -f5 it just displays the 5th word and i need the combination of 5th and 6th, so i tried grep 'the date and time is' 2012-12-07.txt | cut -d\ -f5 -f6 But its error. Now, how to grep the 5th and 6th word with one command I just need the output like 2012-12-07 17:11:50

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  • Setting up separate ctags db's for C/C++ standard libs, boost, and third party libs

    - by Robert S. Barnes
    I want to set up separate ctags databases for various libraries in /usr/include/ for use with OmniCppComplete. The idea is to be able to pull in only the libraries needed for a particular project in the target language - C or C++. For example, I'd like to have one database for the standard C libraries, one for system libraries that might be used by either C or C++ programs ( sockets / networking comes to mind ) one for the standard C++ libs / STL / Boost, and then other databases for various third party libraries such as QT or glib. Then I could pull something in simply by typing set tags+= ~/.vim/somelib.tags in vim. I assume that everything related to the C++ stdlib and STL are in the /usr/include/c++ and that Boost is all in /usr/include/boost. Unfortunately it seems that the standard C libs and system libs are just kind of dumped directly into /usr/include/ with a variety of other stuff. How can I get a list of which files and directories belong to which libs? I'm on Ubuntu 8.04.

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  • How can I determine if a file is read-only for my process on *nix?

    - by user109078
    Using the stat function, I can get the read/write permissions for: owner user other ...but this isn't what I want. I want to know the read/write permissions of a file for my process (i.e. the application I'm writing). The owner/user/other is only helpful if I know if my process is running as the owner/user/other of the file...so maybe that's the solution but I'm not sure of the steps to get there.

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  • Passing enums to functions in C++

    - by rocknroll
    Hi all, I have a header file with all the enums listed (#ifndef #define #endif construct has been used to avoid multiple inclusion of the file) that I use in multiple cpp files in my application.One of the enums in the files is enum StatusSubsystem {ENABLED,INCORRECT_FRAME,INVALID_DATA,DISABLED}; There are functions in the application delcared as ShowStatus(const StatusSubsystem&); Earlier in the application when I made calls to the above function like ShowStatus(INCORRECT_FRAME); my application used to compile perfectly. But after some code was added The compilation halts giving the following error: File.cpp:71: error: invalid conversion from `int' to `StatusSubsystem' File.cpp:71: error: initializing argument 1 of `void Class::ShowStatus(const StatusSubsystem&) I checked the code for any conflicting enums in the new code and it looked fine. My Question is what is wrong with the function call that compiler shows as erroneous? For your reference the function definition is: void Class::ShowStatus(const StatusSubsystem& eStatus) { QPalette palette; mStatus=eStatus;//store current Communication status of system if(eStatus==DISABLED) { //select red color for label, if it is to be shown disabled palette.setColor(QPalette::Window,QColor(Qt::red)); mLabel->setText("SYSTEM"); } else if(eStatus==ENABLED) { //select green color for label,if it is to be shown enabled palette.setColor(QPalette::Window,QColor(Qt::green)); mLabel->setText("SYSTEM"); } else if(eStatus==INCORRECT_FRAME) { //select yellow color for label,to show that it is sending incorrect frames palette.setColor(QPalette::Window,QColor(Qt::yellow)); mLabel->setText("SYSTEM(I)"); } //Set the color on the Label mLabel->setPalette(palette); } A strange side effect of this situation is it compiles when I cast all the calls to ShowStatus() as ShowStatus((StatusSubsystem)INCORRECT_FRAME); Though this removes any compilation error, but a strange thing happens. Though I make call to INCORRECT_FRAME above but in function definition it matches with ENABLED. How on earth is that possible? Its like while passing INCORRECT_FRAME by reference, it magically converts to ENABLED, which should be impossible. This is driving me nuts. Can you find any flaw in what I am doing? or is it something else? The application is made using C++,Qt-4.2.1 on RHEL4. Thanks.

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  • Address of instruction causing SIGSEGV in external program

    - by karramba
    I want to get address of instruction that causes external program to SIGSEGV. I tried using ptrace for this, but I'm getting EIP from kernel space (probably default signal handler?). How GDB is able to get the correct EIP? Is there a way to make GDB provide this information using some API? edit: I don't have sources of the program, only binary executable. I need automation, so I can't simply use "run", "info registers" in GDB. I want to implement "info registers" in my own mini-debugger :)

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  • Small openmp programm freezes sometimes (gcc, c, linux)

    - by osgx
    Hello Just write a small omp test, and it does not work correctly all the times: #include <omp.h> int main() { int i,j=0; #pragma omp parallel for(i=0;i<1000;i++) { #pragma omp barrier j+= j^i; } return j; } The usage of j for writing from all threads is incorrect in this example, BUT there must be only nondeterministic value of j I have a freeze. Compiled with gcc-4.3.1 -fopenmp a.c -o gcc -static Run on 4-core x86_Core2 Linux server: $ ./gcc and got freeze (sometimes; like 1 freeze for 4-5 fast runs). Strace: [pid 13118] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3014, FUTEX_WAIT, 2, NULL <unfinished ...> [pid 13120] <... futex resumed> ) = 0 [pid 13119] futex(0x80d3014, FUTEX_WAIT, 2, NULL <unfinished ...> [pid 13120] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13120] futex(0x80cd798, FUTEX_WAIT, 1, NULL <unfinished ...> [pid 13109] <... futex resumed> ) = 0 [pid 13109] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13109] futex(0x80d3020, FUTEX_WAIT, 251, NULL <unfinished ...> [pid 13118] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13119] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3020, FUTEX_WAIT, 251, NULL <unfinished ...> [pid 13119] futex(0x80d3014, FUTEX_WAKE, 1) = 0 [pid 13119] futex(0x80d3020, FUTEX_WAIT, 251, NULL <freeze> Why do I have a freeze (deadlock)?

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  • Using /dev/tcp instead of wget

    - by User1
    Why does this work: exec 3</dev/tcp/www.google.com/80 echo -e "GET / HTTP/1.1\n\n"&3 cat <&3 And this fail: echo -e "GET / HTTP/1.1\n\n" /dev/tcp/www.google.com/80 cat </dev/tcp/www.google.com/80 Is there a way to do it in one-line w/o using wget, curl, or some other library?

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  • appending text to all files that starts with a string

    - by learner135
    How do I append a string to all the files in a directory that starts with a particular string? I tried, cat mysig >> F* But instead of appending contents of mysig to all files starting with F, it creates a file named "F*". Obviously wildcard doesn't seem to work. Any alternatives? Thanks in advance. Edit: Also how do I delete this newly created file "F*" safely?. Using rm F* would delete all the files starting with F which I wouldn't want.

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  • Need a very simple bash-based webserver for logging XML in HTTP POST

    - by Syffys
    As in title, it's for testing purpose and I need it to be extremely light (1 line to 1 single light file). Here is a XML query sample: XML_QUERY=$(cat <<EOF <?xml version='1.0' encoding='UTF-8'?> <Test></Test> EOF ) curl -H "Content-type: text/xml; charset=utf-8" -H "Soapaction: \"\"" -k -d "${XML_QUERY}" http://localhost:8088 Here are some of the tracks I have found so far even if I wasnt able to adapt them to work as I expect: Netcat minimal webserver: Problem is that my nc does not have the -q option, so the connection is closing before delivering the XML content Netcat Only webserver: Same as above Python based: But does not handle POST Thanks in advance!

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  • fopen() fails to open stream: permission denied, yet permissions should be valid

    - by about blank
    So, I have this error: Warning: fopen(/path/to/test-in.txt) [function.fopen]: failed to open stream: Permission denied Performing ls -l in the directory where test-in.txt is produces the following output: -rw-r--r-- 1 $USER $USER 1921 Sep 6 20:09 test-in.txt -rw-r--r-- 1 $USER $USER 0 Sep 6 20:08 test-out.txt In order to get past this, I decided to perform the following: chgrp -R www-data /path/to/php/webroot And then did: chmod g+rw /path/to/php/webroot Yet, I still get this error when I run my php5 script to open the file. Why is this happening? I've tried this using LAMP as well as cherokee through CGI, so it can't be this. Is there a solution of some sort? Edit I'll also add that I'm just developing via localhost right now. Update - PHP fopen() line $fullpath = $this->fileRoot . $this->fileInData['fileName']; $file_ptr = fopen( $fullpath, 'r+' ); I should also mention I'd like to stick with Cherokee if possible. What's this deal about setting file permissions for Apache/Cherokee?

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  • Identifying the parts of this typedef struct in C?

    - by Tommy
    Please help me identify the parts of this typdef struct and what each part does and how it can be used: typedef struct my_struct { int a; int b; int c; } struct_int, *p_s; struct_int struct_array[5]; my_struct is the...? struct_int is the...? *p_s is the...and can be used to point to what? struct_array is the...? Also, when creating the array of structs, why do we use struct_int instead of my_struct ? Thank You!

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  • Kernel dealing with the section headers in an ELF

    - by uki
    I recently read that the kernel and the dynamic loader mostly deal with the program header tables in an ELF file and that assemblers, compilers and linkers deal with the section header tables. The number of program header tables and section header tables are mentioned in the ELF header in fields named e_phnum and e_shnum respectively. e_phnum is two bytes in size, so if the number of program headers is 65535, we use a scheme known as extended numbering where, e_phnum is set to 0xffff and sh_link field of the zeroth section header table holds the actual count. My doubt is : If the count of program headers exceeds 65535, does that mean the kernel and/or the dynamic loader end up having to read the section table?

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  • GNU Emacs is crashing with -nw

    - by Jack
    When I run emacs with -nw option, the emacs really open, but I can't do more nothing. As if the user input is blocked and no keyboard signal is received and/or interpreted. I've tried run without load .emacs file and some other behaviors: emacs -nw -Q --no-desktop --debug-ini foo.c But makes no difference and strangely the GUI-version(using Gtk) is working fine. My gnu-emacs version is GNU Emacs 23.3.1 Any help to help to fix it is very appreciated.

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  • Run FFmpeg from Shell Script

    - by Abs
    Hello all, I have found a useful shell script that shows all files in a directory recursively. Where it prints the file name echo "$i"; #Display File name. I would instead like to run an ffmpeg command on non MP3 files, how can I do this? I have very limited knowledge of shell scripts so I appreciate if I was spoon fed! :) //if file is NOT MP3 ffmpeg -i [the_file] -sameq [same_file_name_with_mp3_extension] //delete old file Here is the shell script for reference. DIR="." function list_files() { if !(test -d "$1") then echo $1; return; fi cd "$1" echo; echo `pwd`:; #Display Directory name for i in * do if test -d "$i" #if dictionary then list_files "$i" #recursively list files cd .. else echo "$i"; #Display File name fi done } if [ $# -eq 0 ] then list_files . exit 0 fi for i in $* do DIR="$1" list_files "$DIR" shift 1 #To read next directory/file name done

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  • Change workarea size of Linux desktop

    - by nonoitall
    I'm trying to write a taskbar/panel for Linux (like fbpanel or pypanel) using GTK# and am a little hung up. I've created a Gtk.Window to act as the panel and positioned/resized it appropriately. I've also set its WindowTypeHint to Dock so that it remains on top of other windows. So far it 'looks' like a panel. However, if the panel is running and I maximize another window, that window fills the whole desktop - meaning the bottom portion of the window is covered up by my panel. I've gathered that I probably need to change the desktop's workarea. How can I go about doing this in C#? (Preferably using GTK#, but I don't mind using interop if it's necessary.) As a bit of a side point, I'm curious if anyone knows how I would go about 'informing' the window manager about where applications' taskbar buttons are. (For example, if the window manager wants to animate the minimize action so that the window shrinks down to its button on the taskbar, how do I let the window manager know where that button is on the taskbar?)

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  • kernel get stack when signalled

    - by yoavstr
    hi there i write readers and writers where the kernel have to syncronize between them and block writer who already read a massage when i am in the queue waiting I get signal so I do the fallowing while (i_Allready_Read(myf) == ALLREADY_READ || isExistWriter == false ) //while (!(i_Allready_Read(aliveProc,current->pid))) { int i, is_sig = 0; printk(KERN_INFO "\n\n*****entered set in read ******\n\n" ); if (i_Allready_Read(myf) == ALLREADY_READ ) wait_event_interruptible (readWaitQ1, !i_Allready_Read(myf)); else wait_event_interruptible (readWaitQ1, isExistWriter); //printk(KERN_INFO "Read Wakeup %d\n",current->pid); for (i = 0; i < _NSIG_WORDS && !is_sig; i++) { is_sig = current->pending.signal.sig[i] & ~current->blocked.sig[i]; } if (is_sig) { handledClose(myf); module_put (THIS_MODULE); return -EINTR; } } return 0;//success } inline void handledClose(struct file *myf)//v { /* *if we close the writer other writer *would be able to enter to permissiones */ if (myf == writerpid ) { isExistWriter = DOESNT_EXIST; //printk(KERN_INFO "procfs_close : this is pid that just closed %d \n", writerpid); } /* *else its a reader so our numofreaders *need to decremented */ else { removeFromArr(myf); numOfReaders--; } } and my close does nothing ... what did i do wrong?

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