Hello everyone, Could anybody let me know where I can find a manual or an web page that describes the specification for specifying the selective file driven decision functions in Open MPI's mpirun/mpiexec command as explained below ?
> Jelena Pjesivac-Grbovic wrote: >This is an excellent solution if we have only one type of allreduce (large >one). However, if your application has multiple types of allreduce (both >small and large), this may not be a satisfactory solution. In this case, >Open MPI allows you to specify a file which contains rules which function >to use when. This option has slight learning curve and I am currently >evaluating its effectiveness, but if you are interested - I will send you >more documentation about it. >Selective file driven decision functions Another alternative to forcing the >complete collective operations is to force only parts of the decision space in >a >semi-fixed manner. An example of such a usage scenario would be in the case of >a user having tuned an MPI collective for a range of input parameters (message >size, communicator size) either manually or via some automated tool [6]. The >user could then tell the MPI collective component to use these values within a >set range by supplying a file that contains as many data points as the user >knows. >To decrease both storage and evaluation time the file contents are stored using >a run-length technique that effectively only stores the switching points for >each >algorithm. An example version for an MPI Alltoall operation is shown below: >1 # num of collectives >3 # ID = 3 Alltoall collective (ID in coll_tuned.h) >2 # number of com sizes >1 # comm size 1 >1 # number of msg sizes 1 >0 1 0 0 # for message size 0, linear 1, topo 0, 0 segmentation >8 # comm size 8 >4 # number of msg sizes >0 1 0 0 # for message size 0, linear 1, topo 0, 0 segmentation >32768 2 0 0 # 32k, pairwise 2, no topo or segmentation >262144 1 0 0 # 256k, use linear 1, no topo or segmentation >524288 2 0 0 # message size 512k+, pairwise 2, topo 0, 0 segmentation ># end of first collective Best regards, Norio
