Cobra Forums

"""
ParallelFor in cobra from <!-- m --><a class="postlink" href="http://coding-time.blogspot.com/2008/03/implement-your-own-parallelfor-in-c.html">http://coding-time.blogspot.com/2008/03 ... -in-c.html</a><!-- m -->
"""
use System.Threading

sig ForDelegate(i as int)
sig ThreadDelegate

class Parallel
    """
        Parallel for loop. Invokes given action, passing arguments
        fromInclusive - toExclusive on multiple threads.
        Returns when loop finished.
    """
    
    def for(fromInclusive as int, toExclusive as int, action as ForDelegate) is shared
        """
        ChunkSize = 1 makes items to be processed in order.
        Bigger chunk size should reduce lock waiting time and thus increase paralelism.
        """ 
        chunkSize = 4    # number of process() threads
        threadCount = Environment.processorCount
        cnt = fromInclusive - chunkSize
 
        # processing function
        # takes next chunk and processes it using action
        process as ThreadDelegate = do
            while true
                cntMem = 0
                lock Parallel.getType
                    # take next chunk
                    cnt += chunkSize
                    cntMem = cnt

                    # process chunk
                    # here items can come out of order if chunkSize > 1
                    for i in cntMem : cntMem + chunkSize
                        if i >=  toExclusive, break
                        action(i)
 

        # launch process() threads
        asyncResults = IAsyncResult[](threadCount)
        for i in 0 : threadCount
            asyncResults[i] = process.beginInvoke(nil, nil)  # line 45

        # wait for all threads to complete
        for i in 0 : threadCount
            process.endInvoke(asyncResults[i])  # line 49
        
    
    def main is shared
        Parallel.for(0, 100, do(i as int))
            # Your parallel code
            Thread.sleep(100)
            Console.writeLine(i)

#asyncResults[i] = process.beginInvoke(nil, nil)
asyncResults[i] = sharp'process.BeginInvoke(null, null)'

#process.endInvoke(asyncResults[i])
sharp'process.EndInvoke(asyncResults[i])'