Programming :: VTALRM In Multi-threaded Programs?
Apr 20, 2011
I ran into an inconsistency in handling timers (VTALRM) between AMD and intel platforms with threads. My understanding was that the timers are per process. I discovered I must call setitimer in the thread on intel though. AMD allows me to make the setitimer call once in the main thread as expected. The code below demonstrates the issue. I must add the code in the INTEL define for it to work properly on intel cpu's. Am I missing something dumb??
[Code]...
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Aug 12, 2010
For quite some time now, I've been trying to implement a multi-threaded or forked TCP server to perform the following action:1) Listen for new connections on all ip addresses on a specific port.2) Wait for a new connection to arrive3) When a new connection coms in, fork or thread to free up the listening process so it can go back to #2.When handling a client after it's been forked/threaded4) Get the connected client's ip address.5) Perform some in-house processing;6) Read the data sent from the client (checking for http connections)7) Perform some more processing;8) Write some data back to the client based on the above processing9) Close the socket/thread/forkI've tried implementing an solution similar to the multi-threaded example show here http://perl.active-venture.com/pod/p...-sockets.html; as well as looking at the CPAN solutions Net:aemon and POE::Component::Server::TCP but these don't seem to give me the information needed.The active-venture solution provides me with what I need, but randomly exits without reason/error and when attempting to change the 'for' loop to a 'while' loop, it keeps throwing up different errors.
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Jul 24, 2010
I'm trying to add local sockets in my multi-threaded application in order to exchange data between threads. The only problem I got is that most of the information available on the net is related to internet oriented socket programming whileI want to perform local connections. got a thread that does the sniffing via libpcap. And I would like that thread to send each captured packet to a second thread that will analyse the packetof the thread implementations is written in separate .h file.Or maybe there is a more effective method of exchanging data between threads
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Jun 15, 2010
writing multi threaded programs in C,C++.
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Apr 7, 2011
Using Ubuntu server 10.04.2 64-bit all up to date.
I am running multi-threaded processes. These use OpenMP in my own code and the multi-threaded ACML maths library. When run in the foreground, everything is fine i.e. if I have set
export OMP_NUM_THREADS=8
then when I start all 8 cores are in use and things whizz along. However, when running overnight and logged out using e.g. 'at now + 1 minute' then the command, I am only getting about 130% CPU and it slows down accordingly. I have tried renice'ing and calling from within a bash script in case sh is doing something odd but nothing seems to solve it. I am sure that in the recent past this wasn't the case.
The libraries being used are shared versions in case that might have any bearing.
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Apr 29, 2011
I am implementing a proxy server in c++. It is multithreaded(posix).Used CPU : Xeon(8core) Thread number : 8 One main thread, and other 7 thread created by the main thread. The main thread always listen to ports. When the main thread gets a client data it push the request in a queue[there are one queue(total 7) for each thread] based on ip and then give a signal to the appropriate thread. Then that thread gets the request from it's queue and process data and then forward the data to a appropriate destination.
There is another important thing, I assign each thread excluding the main thread to individual core by using affinity.The main thread listens to 5 ports. Test environment: We run the server. The client sends audio data at a particular rate.
1. The main thread CPU usage gets overloaded (above 80%) after a certain load from client.
2. Other cores remain about 0-10%.
The thing is that we want to distribute the load among all the cores equally by multithreading. But how can we do this ? Can the listening task of ports also be distributed ? I need an efficient algorithm for load balancing among threads. The data sent and receive rate of server is about 8.5MB/s. How can we improve this ? we are using gigabit LAN card. When the server only receive data from client it can receive data above 80MB/s. But when it both receives and sends data simultaneously it only manage upto 8.5MB/s.
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May 18, 2011
So I have built a program that takes a picture from two cameras every second and converts them both to jpeg format. The problem is that currently it takes ~2 seconds to convert a single raw photo to jpeg format, thus every second I add another raw photo (30 MB) to ram waiting to be converted to jpeg. So, theoretically the conversion to jpeg is running on a single core with hyperthreading, would I see better performance running the exact same process (a program pulling from a queue and converting to jpeg) running as a single process, or two concurrent processes? (both processes running on the same core, (so 1 thread on one clock cycle, the other on the other... (or one thread running on 1 core and the other on another core. What other steps would you take to improve the performance so there would no longer be a race condition?
-Currently using QT
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Sep 18, 2010
I am creating a program that need menu with multi selection option for shell (CLI).I am using of Bash scripts.something that will look like that:
Menu:
[ ] option 1
[x] option 2
[code]...
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Jul 28, 2010
I do a lot of scientific work - mainly in C/C++ but want to do some of the calcs in python, however I am finding it a problem with the lack of dimensionality. I frequency have a list of n particles and a multi-dim array for each particle and want to be able to access directly any component with ease. How best to go about this...
my prop = [n][x][y][z]
I might need a particular value and then to update that. I do not want to have to deal with lists etc etc as this feels rather cumbersome, adding, removing etc. There must be an easy way.
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Apr 30, 2010
I have a multi-dimensional array like so:
Code:
Array (
[0] => Array (
[0] => Eleven
[1] => NumberEleven
[2] => 11 )
[1] => Array (
[0] => Twelve
[1] => NumberTwelve
[2] => 12 )
[2] => Array (
[0] => AnotherEleven
[1] => Eleven,Again
[2] => 11 )
I need to sort it by array[ $key ][ 2 ] so that it is sorted like so:
Code:
Array (
[0] => Array (
[0] => Eleven
[1] => NumberEleven
[2] => 11 )
[1] => Array (
[0] => AnotherEleven
[1] => Eleven,Again
[2] => 11 )
[2] => Array (
[0] => Twelve
[1] => NumberTwelve
[2] => 12 )
I've looked at the php array docs the closet thing I found was array_multisort which won't work for my above requirements, does anyone have any insight to how to sort this way?
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Sep 17, 2010
I am parsing through XML documents with a PHP script and creating an array because, as far as I know, I can manipulate arrays better than the features DOM gives me. That part is not as important, though. The array it produces though is multi-dimensional, but somewhat inconsistent. If I have the following XML:
PHP Code:
<domains> <domain>
<title>google.com</title> <bookmarks>
<bookmark>maps.google.com</bookmark>
<bookmark>news.google.com</bookmark>
<bookmark>mail.google.com</bookmark>
</bookmarks> </domain> <domain>
<title>bankaccount.com</title>
<bookmarks> <bookmark>login.bankaccount.com</bookmark>
</bookmarks> </domain> </domains>
To call the first bookmark from the first domain, it would be:
PHP Code:
$array['domains']['domain'][0]['bookmarks']['bookmark'][0]
To call the first bookmark from the second domain, it would be:
PHP Code:
$array['domains']['domain'][1]['bookmarks']['bookmark']
The problem is, I want to simply call bookmarks through a simply 'foreach()' or 'for()' function and the lack of consistency might be a problem, but the fact that some levels have a '0' array key and others do not is causing a problem.
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Jun 24, 2011
I have an ATI Radeon HD 3300 on-board video chipset, and an ATI Radeon HD 4350 PCI card. What I want is to have both displays available from one mouse/keyboard. I want to play media on one and have the other as my main desktop.The problem is that with Xinerama enabled, KDE desktop effects do not work (KDE says XComposite and XDamage are not available, even though I explicitly enabled them as extensions in the xorg.conf file), and performance is quite bad. Without Xinerama enabled, performance is great, desktop effects work great, but there's a lot of trouble with full-screen video, and the KWin window manager does not apply in the second display (although I can run a second instance of KWin on :0.1).
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Mar 17, 2009
I just started programming in PHP so I haven't figured out how to do this yet, but I have a multi-dimensional array that I need to sort by one column. That's fine...but I need the sort to ignore case! Right now I have it sorted by 'name' (the other column is 'uid').
The problem is that by the default the sort is case-sensitive so the array looks like this:
Code:
Apple 4015
Banana 4011
Cherry 4045
avocado 4046
I want to be able to sort the the 'name' column in a case-insensitive manner so that the array actually looks like:
Code:
Apple 4015
avocado 4046
Banana 4011
Cherry 4045
How to accomplish this? Just FYI I'm not actually sorting the PLUs for fruits...but it was a simple example. I'm actually doing this for a Facebook application.
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Jan 30, 2010
I have a 2GB file which is a dd image of a block device. The block device (a USB-connected flash memory) contains multiple partitions, and therein lies the problem. I want/need to access the various partitions in the image file, but need to do this without actually using a physical flash memory device. If the image was that of a single partition, I could simply mount it on a loop device, and access the filesystem as necessary. However, I can find no kind of virtual block device upon which to write/mount the image.
I've searched the net exhaustively for anything that would seem to allow me to do what I need, but without even a sniff of success. Sadly, I have seen bits of information that suggest "you can't get there from here". Even the outstanding dd tutorial by AwesomeMachine on LQ didn't help. Anyone know of a kind of virtual block device on which a multi-partition image can be written and mounted? Or any other way I can access individual partitions (with various filesystem types on each) and then re-assemble them back to a single image?
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Apr 15, 2010
I am curious if there is a way to describe and use variable sized multi-dimensional arrays in C using pointers. I mean, for 1-dimensional array e.g. I can use the following piece of code:
...
int i , N;
int *array;
scanf("%d", &N);
array = (int*) malloc(N*sizeof(int));
for (i=0; i<N; ++i) array[i] = i; // Assigning values to the array
for (i=0; i<N; ++i) printf("%d ", array[i]); // Printing the assigned values
free (array);
...
But what about the two dimensional array[N][M] ? I guess I have to use a double pointer e.g: int **array. But how exactly? Note that I use C90 and not C99.
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Apr 26, 2009
I would like to have a script that will do a search in an XML file for a specific block of XML code and replace it with a different block of XML code using the Windows build of GNU Sed 4.1.5.
Here's the text I want to find:
Code:
And here's what I want to replace it with:
Code:
There is however a lot of stuff in there that would mess up sed, and the one example from the sed FAQ (from the Sourceforge site) that looked promising and easy enough to figure out (4.23.3. Try to use a block of "literal strings") fails with this error message: sed: file blockrep.sed line 18: unterminated `s' command
Anyone got any ideas, or even an alternate program that can do this? (Preferably one that I can automate.)
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Mar 1, 2010
I am new to Programming. I would like to learn some multi threading in C. how to start. I read tutor about multi threading, but not getting correctly.
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May 12, 2011
i got basic knowledge about creating a single child from a parent using fork(). But when it comes into creating multiple children, i am simply stuck. I am trying to create two processes from a parent and it would wait for both two processes to finish. my attempt is as below
[Code]....
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Mar 21, 2011
Anyone successfully using VNC client on a Mac to control a Debian server?I have the vncserver setup on the Debian machine properly. But I'm having problems connecting to it from both a PowerMac running Tiger and a MacBookPro running leopard.I can connect no problem from a machine running Slack12.2, have not setup port forwarding on my router to connect remotely yet.My Debian machine is running the latest stable release of squeeze with KDE4.I originally tried this with RealVNC Enterprise for OSX but I'm not gonna buy it so I need another alternative after the 30 day trial ends as they have no free version for OSX.
The situation is that I do freelance graphic design on the PowerMac with Cinema4D and Photoshop so I spend most of my time on that machine which is located in my home studio in my attic. Aside from the MacBook and a Dell desktop(family machine)all my other machines and network hardware are in the basement. So to go from the attic to the basement everytime I need to do something on another machine is not practical, and the only other machine I need to access on a regular basis is the Debian box in the basement, this makes the most sense.
I also have a 14 year old living in the house and he's fascinated by all this and will meddle in anything he gets the chance to so all the Linux machines and network hardware need to be behind lock and key.
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Jun 30, 2009
I'm starting work on a little project that uses alot of languages separately (i.e no interaction between languages. Does anyone have any experience like this and could pass on some recommendations as to best practises? I'm thinking either have a eclipse-project for each language stored under a single svn repo, or individual projects for each problem.
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Aug 3, 2010
I'm wanting to mod some PHP files across a hierarchy and thought I'd drive it with find + grep + xargs
I built up a command line which I was confident would do the job, but now can't save the results.
First I tried this:
Code:
find . -name *.php | xargs grep serialize | cut -d: -f1| sort -u | xargs sed -i s/serialize/serialise/g
but that didn't work:
Code:
sed: illegal option -- i
so I thought I'd try using
Code:
[Code].....
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Nov 11, 2009
I have a large file 'NS0923.csv' with data like the following. There are two records in this multi-record sample.
Code:
E60898,4578910,03/06/09,BEN BOYD RD,61,82,,,127,3,,52000.3046.001,3155,4.00,,PLT,1356,1.00,05/06/09,Y,Y,0551
,,,,,,,,,,,,4057,1.00,CLEAN CAR SHARE SIGN,LAB,0551,1.00,,,,
[code]....
2. I still have to create a file 'transaction.csv' that should retrieve data from $13 - $15 with the identifying column $1. Required output:
Code:
E60898,4057,1.00,CLEAN CAR SHARE SIGN
3. And finally another file 'quantity.csv'. Retrieving data from $16 - $18 with identifier $1. Required output:
Code:
E60898,PLT,1356,1.00
E60898,LAB,0551,1.00
E60898,LAB,3065,1.00
[code]....
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May 12, 2010
I've got a set of objects (all of the same type). I'm trying to think of a good way to divide it into equivalence classes, with equivalence of two objects defined as meaning a specified set of attributes are equal for both objects. More concretely, I've got:
- a Java class with around 50 fields
- a bunch of instances of the class
I want:
- to divide the instances into a few sets
- in each set, each instance has field 1 - field 5 equal to fields 1-5 of the other instances in the set.
The method I've come up with is to generate a hashcode for each instance based on the hashcodes of fields 1-5*, and map the hashcode to one of my sets. Ignoring problems with potential hashcode collisions (which I'm expecting to be too rare to worry about for now), does that sound reasonable? It seems simple enough, but I'm wondering if there's a simpler method I haven't thought of.
* I'll generate the hashcode using a method based on Eclipse's generic hashcode method, which looks like this:
Code:
public int hashCode() {
final int prime = 31;
int result = 1;
[code]....
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Apr 11, 2011
I have written a simple script which has to find required patterns from a bunch of files ( where each file is around 2 GB each,which contain the output of seq 1 10000000000000) on an 8 core machine.I am current forking 6 child processes which run simultaneously on 6 cores of the processor & have to search for the required pattern in 6 different files & inform the parent process when a pattern is found using a PIPE.
The problem is,when a child process is done reading a text file looking for a pattern,it is becoming a zombie process.It exits cleanly when i put a $SIG{CHLD} = "IGNORE"; in the script.Can any one tell me whats going on & how do i improve the communication between child and parent processes?
Code:
#!/bin/perl
use strict;
[code]...
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Sep 17, 2010
Now that Ubuntu 10.04 has multi-touch capabilities built-in, if I do not have a multi-touch screen or surface device, can I get 2 USB mice and get 2 pointers on the screen? One for the right hand and one for the left hand as I am ambidextrous, and would find it very convenient to have 2 mice.
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Sep 12, 2011
Im running 64bit centos 5.6 and using virt-manager.On one of my guest OS's, Windows 7, The max Physical CPUs is 2, you can have unlimited CPU Cores however. (like my machine i use for work has 1, 4 core processor).The issue im having is xen only allows you to set the vcpu arguemnet in your xen config file. How can i set it so that 1 CPU has several Cores just as windows would recognize this machine if i were installing directly to the hardware vs via a VM.Ive searched for 2 days staright trying to address this issue, very little progress, Does anyone know where a XEN support forum is? all i get is the citrix xen support forums.
here is the best info i have found on this, but i dont know how to change this for my CPU to work, when i enter this in my xen config it essentially ignores it and just takes the value of vcpu= so windows shows 2 CPUs each with ONLY one core. Id like 1 or 2 CPUS showing Several cores.The physical Hardware is 2x Xeon 5300 Quad Core CPUs.
> # Expose to the guest multi-core cpu instead of multiple processors
> # Example for intel, expose a 8-core processor :
> #cpuid=['1:edx=xxx1xxxxxxxxxxxxxxxxxxxxxxxxxxxx,[code]........
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Jul 1, 2010
I need a loop that pulls out the user name into a variable and then pulls out the LastUpdate field into another variable so I can then perform a comparison against the last update field. Requirements are AIX tools including AWK, SED and Perl I am writing a script to check AIX users password expiration dates and if they are within the alerting period (ie. 7 days etc) it will email the user. I will release the full script into the public domain once completed. The text file I want to parse is formatted like:
Code:
colettel:
password = XSON0m4SdIQDw
lastupdate = 1260829398
andrewwa:
[code].....
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Nov 8, 2010
I am going through a multi-step process to produce output files, which involves 25,000 greps at one stage. While I do achieve the desired result I am wondering whether the process could be improved (sped up and/or decluttered).input 1set of dated files called ids<yyyy><mm> containing numeric id's, one per line, 280,000 lines in total:
Code:
123456
999996
[code]....
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Nov 29, 2010
I've always thought that the idea was very cool, but I get restricted by the way distros think that "httpd" and the like are the only things that should go into a runlevel - I mean Fedora doesn't even let you turn off the GUI!I want to do some lower-level hacking than that, so can someone help me?
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May 3, 2011
i have two c++ programs, first one captures network packet from eth interface and save it in a file, second one uses this generated file for its purposes, data stream always exists then first program should always be running, although second program cannot read the file while the first program is writing in it, then i need to define a lock which can be checked by both progs before read/write, how is it possible to define this kind of lock in linux?
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