Howard,
i made PR 593 https://github.com/open-mpi/ompi/pull/593 in order to fix
this.
George,
could you please review this ?
Cheers,
Gilles
On 5/20/2015 12:57 PM, Howard Pritchard wrote:
HI Gilles,
First a disclaimer - I do not know what the intended design was nor
where the design document
for this feature is located.
However, I would certainly prefer that if the communicator size wasn't
specifically specified
in the rule file, a fall back do-no-harm algorithm would be selected.
Following the KISS principal I would go with 2) returning a NULL rule when
there is no matching size in the rule file for the communicator in
question.
Howard
2015-05-19 20:05 GMT-06:00 Gilles Gouaillardet <gil...@rist.or.jp
<mailto:gil...@rist.or.jp>>:
Folks,
this is a follow-up of a discussion on the user ML started at
http://www.open-mpi.org/community/lists/users/2015/05/26882.php
1) it turns out the dynamic rule filename must be "sorted" :
- rules must be sorted by communicator size
- within a given communicator size, rules must be sorted by
message size
if not, some rules are silently skipped, which is counter
intuitive imho.
2) the algo picks the rule with the higher communicator size less
or equal than the current communicator size (same thing for
message size).
The exception is if there are no such rule, the first rule is
selected.
for example, if the config file has rules for comm size 4, 8 and 16
comm size 4 => pick rule for comm size 4
comm size 5 => pick rule for comm 4
comm size 8 => pick rule for comm 8
*but*
comm size 2 => pick rule for comm size 4 (!)
imho, this is also counter intuitive.
i would have expected no rule is picked and the default behaviour
is used.
Same thing applies for message sizes.
Is this the intended design ?
1) can be solved by inserting some qsort calls after parsing the
config file.
2) can be solved by returning a NULL rule instead of the first
rule ( or by automatically inserting a rule for comm size 0 (and
message size 0) if no such rule is present in the config file).
any thoughts ?
Cheers,
Gilles
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