Having trouble with parallel Haskell
marlowsd at gmail.com
Thu Jun 5 05:47:45 EDT 2008
Bryan O'Sullivan wrote:
> Isaac Dupree wrote:
>> (no idea if that's relevant, though)
> I can't tell either. It doesn't seem to make a difference, at any rate.
> By the way, I notice that the threaded RTS blocks signals for long
> periods of time when I run this program. If I hit control-C, it takes
> several seconds for the program to notice.
This is usually a symptom of a program that does a lot of allocation-less
computation (or also, long GCs). When the program isn't allocating, the
scheduler never runs, and ^C doesn't get serviced.
Allocation-less computation will also hurt parallelism, because the
load-balancing only happens when the scheduler runs. This often crops up
when people try to parallelism small benchmarks (e.g. fib). It's certainly
a problem, and we don't have a good solution yet.
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