parList implementation question

Marcus D. Gabriel marcus at
Sun Dec 20 08:57:52 EST 2009

Well, I finally put in place 6.12.1 and read the documentation for
Control.Parallel.Strategies.  All of my code for the application described
below uses Done, demanding, sparking, (>|), and (>||) which are deprecated
and which is what I used.  Additionally, I need to understand Eval first
to change my code.

No point in responding until I determine what this means.

Thanks nevertheless,
- Marcus

Marcus D. Gabriel wrote:
> Denis Bueno wrote:
>> On Fri, Dec 18, 2009 at 11:31, Marcus D. Gabriel <marcus at> wrote:
>>> than parList via parMap.  For example, in one experiment, parMap
>>> with parList run at 0.81 the time of the serial solution whereas
>>> forceParMap with forceParList run at 0.58 the time of the serial
>>> solution.  This is to say, forceParList completed in 0.72 the
>>> time of parList.  So,
>> I don't know your application, so it's hard to interpret your numbers.
>> Are you sure those measurements are statistically significant?
> The particular example that I gave was a straightforward
> searchDepthFirst(1) algorithm. To parallelise it, I choose the
> initial, simple approach to determine the first list of successor
> nodes from an initial node and use parMap to apply the serial
> algorithm searchDepthFirst to this list and then reduce (concat)
> the list.
> With some RTS tuning and using a dedicated dual-core system, I was
> able for the problem above to reproduce the numbers that I cite
> above consistently to within about plus or minus a factor of 0.01.
> I have played with variations of this class of problem but not
> generally compared parList with forceParList across a broader class
> of problems.
> I like your question above.  It helped me formulate this question:
> Is what I observed above significant or random?  I hope it is not
> random.
> I guess the deeper question is how does one determine with
> confidence that
>   parallised serial algorithm + startegy1 works for problem class1
> and
>   parallised serial algorithm + startegy2 works for problem class2
> where both are better than the serial case for their respective
> class of problems across a given range of operating environments,
> e.g., -N2 to -N8 for 2 to 8 cores.
> - Marcus
> (1) "Algorithms, A Functional Programming Approach" by Fethi Rabhi
> and Guy Laplame.  ISBN 0201-59604-0.
  Marcus D. Gabriel, Ph.D.                         Saint Louis, FRANCE            mailto:marcus at
  Tel: +                   Portable: +

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