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Subject: Re: [OMPI users] scaling problem with openmpi
From: Pavel Shamis (Pasha) (pashash_at_[hidden])
Date: 2009-05-20 09:44:02


> The correct MCA parameters are the following:
> -mca coll_tuned_use_dynamic_rules 1
> -mca coll_tuned_dynamic_rules_filename ./dyn_rules
Ohh..it was my mistake....

>
> You can also run the following command:
> ompi_info -mca coll_tuned_use_dynamic_rules 1 -param coll tuned
> This will give some insight into all the various algorithms that make
> up the tuned collectives.
>
> If I am understanding what is happening, it looks like the original
> MPI_Alltoall made use of three algorithms. (You can look in
> coll_tuned_decision_fixed.c)
>
> If message size < 200 or communicator size > 12
> bruck
> else if message size < 3000
> basic linear
> else
> pairwise
> end
Yep it is correct.
>
> With the file Pavel has provided things have changed to the following.
> (maybe someone can confirm)
>
> If message size < 8192
> bruck
> else
> pairwise
> end
You are right here. Target of my conf file is disable basic_linear for
medium message side.

Pasha.