Re: pthreads condition variables

[Matthias Scheler <tron%zhadum.org.uk@localhost>]

On Tue, Nov 17, 2009 at 07:53:09PM +0000, raymond.meyer%rambler.ru@localhost 
wrote:
> I want to use all 256 threads to perform some computation in parallel.
> 
> 1. create 256 threads
> 2. threads go to sleep waiting for work
> 3. partition data into 256 parallel regions
> 4. signal all threads to process data
> 
> When threads go to sleep on line 2, they execute:
> 
> pthread_cond_wait(&cond, &mutex)
> 
> When the main thread signals all threads on line 4, it executes:
> 
> pthread_cond_broadcast(&cond)

Why don't you use pthread_cond_signal() and let one worker thread
pick up one work item.

> Because the data is partitioned into 256 parallel regions, each thread
> works on a different data set, hence no need for mutual exclusion.

You don't necessarily have to have a fixed assignment between thread
and data partitions. You only have to make sure that at any time
only one thread access a partition.

        Kind regards

-- 
Matthias Scheler                                  http://zhadum.org.uk/