Of course !!! ;)
First set coll_tuned_use_dynamic_rules to 1, and then use
coll_tuned_dynamic_rules_filename to specify a file containing the selection
logic. This is kind of tricky to write, so we don't advertise it to widely. I
added an example below, contact me privately if you need more info.
Thanks,
george.
1 # num of collectives
3 # ID = 3 Alltoall collective (ID in coll_tuned.h)
1 # number of com sizes
64 # comm size 8
2 # number of msg sizes
0 3 0 0 # for message size 0, bruck 1, topo 0, 0 segmentation
8192 2 0 0 # 8k+, pairwise 2, no topo or segmentation
# end of first collective
On Apr 3, 2012, at 09:01 , Pavel Mezentsev wrote:
> Is there a way to specify collective depending on the size of the message and
> number of processes?
>
> Regards,
> Pavel Mezentsev
>
> 2012/4/3 George Bosilca <bosi...@eecs.utk.edu>
> Roswan,
>
> There a re simpler solutions to achieve this. We have a built-in mechanism to
> select a specific collective implementation. Here is what you have to add in
> your .openmpi/mca-params.conf (or as MCA argument on the command line):
>
> coll_tuned_use_dynamic_rules = 1
> coll_tuned_bcast_algorithm = 6
>
> The first one activate the dynamic selection of collective algorithms, while
> the second one force all broadcast to be of the type 6 (binomial tree). Btw,
> once you set the first one, do a quick "ompi_info --param coll tuned" to see
> the list of all possible options for the collective algorithm selection.
>
> george.
>
> On Apr 2, 2012, at 23:10 , roswan ismail wrote:
>
>> Hi all..
>>
>> I am Roswan Ismail from Malaysia. I am focusing on MPI communication
>> performance on quad-core cluster at my university. I used Open MPI-1.4.3 and
>> measurements were done using scampi benchmark.
>>
>> As I know, open MPI used multiple algorithms to broadcast data (MPI_BCAST)
>> such as binomial, pipeline, binary tree, basic linear and split binary tree.
>> All these algorithms will be used based on message size and communicator
>> size. For example, binomial is used when message size to be broadcasted is
>> small while pipeline used for broadcasting a large message.
>>
>> What I want to do now is, to use fixed algorithm i.e binomial for all
>> message size. I want to see and compare the results with the default
>> results. So, I was modified coll_tuned_decision_fixed.c which is located in
>> open mpi-1.4.3/ompi/mca/coll/tuned by returning binomial algorithm for all
>> condition. Then I recompile the files but the problem is, the results
>> obtained is same as default. It seems I do not do any changes to the codes.
>>
>> So could you guys tell me the right way to do that.
>>
>> Many thanks
>>
>> Roswan Binti Ismail,
>> FTMK,
>> Univ. Pend. Sultan Idris,
>> Tg Malim, Perak.
>> Pej: 05-4505173
>> H/P: 0123588047
>> iewa...@gmail.com
>> ros...@ftmk.upsi.edu.my
>> _______________________________________________
>> devel mailing list
>> de...@open-mpi.org
>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>
>
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