pthreads question

[ResidentBiscuit]

So I've got a programming assignment that just multiplies two matrices together, and stores the result in a third. Supposed to be done using threads, but I have no idea how to start. I understand what a thread is, but I guess I just don't know how to actually use threads when programming. I've hit this wall in my head where I can't even comprehend what's supposed to happen. Any tips?

[naraku9333]

Maybe have a thread that does the calculations for each column or row of the product matrix.

Edit: Links...
This has pseudo code
http://stackoverflow.com/questions/5290190/matrix-multiplication-using-threads

These have code
http://www.daniweb.com/software-development/cpp/threads/386246/c-matrix-multiplication-with-threads
http://www.cplusplus.com/forum/general/28599/
http://stackoverflow.com/questions/5290190/matrix-multiplication-using-threads

NOTE: I do not know if any of the code in those links will work but either way they should get you in the right direction.

[codewalker]

you can use pthreads or if you have a C++11 capable compiler (clang 3.1 later, gcc 4.7.1 later, Visual Studio 2012 etc) then you can use the built in threads of C++11 std.

Here is how threads in C++11 are created

std::thread t1 (thread_function, thread_argument); 
//You can pass multiple arguments to the thread like std::thread t1 (thread_function, int_argument, vector_argumane, object_argument );

//Some code in main thread

t1.join(); //wait for the thread to complete 

You need to #include<thread>. More information here http://en.cppreference.com/w/cpp/thread/thread
If you need thread synchronisation (who doesn't?) then look at http://en.cppreference.com/w/cpp/thread/mutex

[Grey Wolf]

ResidentBiscuit, this may be of use:
https://computing.llnl.gov/tutorials/pthreads/

[ResidentBiscuit]

Ah thanks these links are great! I understand what the program needs to get done, I was just having trouble of actually using the threads. We covered threads in theory but not with how they work at all. Didn't know that you created a thread and passed it a function to perform. Not really sure what I was thinking for how threads worked -_-

[iHutch105]

I've used the link that Grey Wolf provided for threading before. Absolute gold.