Parallel foreach gets executed one after another
Thorsten Sommer via Digitalmars-d
digitalmars-d at puremagic.com
Sat Sep 16 13:57:08 UTC 2017
Thank you for helping me so much in the last thread concerning
our AI library
(https://email@example.com). Thanks to you, we can now debug our AI library with GDB. My suspicion was confirmed: At least one of our parallel foreach loops will only be processed item by item instead of parallel.
It is the loop that contains the largest workload: An external
process is started for each agent. I log the PID, so I see that
the processes are started one after the other.
Our foreach loops are constructed as:
auto taskPool = new TaskPool();
foreach (n, individual; taskPool.parallel(individuals,
pipes = pipeProcess(args, Redirect.stdout | Redirect.stdin);
The looped individuals are sourced by such a statement:
return this.individuals.filter!( [...] ).array;
Currently, for debugging, params.workUnitSize4ParallelExecution
is set to 100 and individuals contain approx. 10 agents.
Therefore, we would expect 10 external processes to be started
simultaneously. Each process runs approx. 4 seconds. Accordingly,
the processing should take about 4 seconds instead of 40 seconds.
Do you have any ideas what might be the reason for this? If you
don't know a solution, then maybe approaches to further
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