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From: Terry D. Dontje (Terry.Dontje_at_[hidden])
Date: 2007-08-31 13:36:52


Ok, I have an update to this issue. I believe there is an
implementation difference of sched_yield between Linux and Solaris. If
I change the sched_yield in opal_progress to be a usleep(500) then my
program completes quite quickly. I have sent a few questions to a
Solaris engineer and hopefully will get some useful information.

That being said, CT-6's implementation also used yield calls (note this
actually is what sched_yield reduces down to in Solaris) and we did not
see the same degradation issue as with Open MPI. I believe the reason
is because CT-6's SM implementation is not calling CT-6's version of
progress recursively and forcing all the unexpected to be read in before
continuing. CT-6 also has a natural flow control in it's implementation
(ie it has a fixed set fifo for eager messages.

I believe both of these characteristics lend CT-6 to not being
completely killed by the yield differences.

--td

Li-Ta Lo wrote:

>On Thu, 2007-08-30 at 12:45 -0400, Terry.Dontje_at_[hidden] wrote:
>
>
>>Li-Ta Lo wrote:
>>
>>
>>
>>>On Thu, 2007-08-30 at 12:25 -0400, Terry.Dontje_at_[hidden] wrote:
>>>
>>>
>>>
>>>
>>>>Li-Ta Lo wrote:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>On Wed, 2007-08-29 at 14:06 -0400, Terry D. Dontje wrote:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>hmmm, interesting since my version doesn't abort at all.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>Some problem with fortran compiler/language binding? My C translation
>>>>>doesn't have any problem.
>>>>>
>>>>>[ollie_at_exponential ~]$ mpirun -np 4 a.out 10
>>>>>Target duration (seconds): 10.000000, #of msgs: 50331, usec per msg:
>>>>>198.684707
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>Did you oversubscribe? I found np=10 on a 8 core system clogged things
>>>>up sufficiently.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>Yea, I used np 10 on a 2 proc, 2 hyper-thread system (total 4 threads).
>>>
>>>
>>>
>>>
>>>
>>Is this using Linux?
>>
>>
>>
>
>
>Yes.
>
>Ollie
>
>
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