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
