They can also use RankMapping policy for a precise mapping .
On 4/25/08, Jeff Squyres <jsquy...@cisco.com> wrote: > > Kewl! > > I added ticket 1277 so that we are sure to document this for v1.3. > > > > On Apr 23, 2008, at 11:09 AM, Ralph H Castain wrote: > > > I added a new "loadbalance" feature to OMPI today in r18252. > > > > Brief summary: adding --loadbalance to the mpirun cmd line will > > cause the > > round-robin mapper to balance your specified #procs across the > > available > > nodes. > > > > More detail: > > Several users had noted that mapping byslot always caused us to > > preferentially load the first nodes in an allocation, potentially > > leaving > > other nodes unused. If they mapped bynode, of course, this wouldn't > > happen - > > but then they were forced to a specific rank-to-node relationship. > > > > What they wanted was to have the ranks numbered byslot, but to have > > the ppn > > balanced across the entire allocation. > > > > This is now supported via the --loadbalance cmd line option. Here is > > an > > example of its affect (again, remember that loadbalance only impacts > > mapping > > byslot): > > > > no-lb lb bynode > > node0: 0,1,2,3 0,1,2 0,3,6 > > node1: 4,5,6 3,4 1,4 > > node2: 5,6 2,5 > > > > > > As you can see, the affect of --loadbalance is to balance the ppn > > across all > > the available nodes while retaining byslot rank associations. In > > this case, > > instead of leaving one node unused, we take advantage of all available > > resources. > > > > Hope this proves helpful > > Ralph > > > > > > _______________________________________________ > > devel mailing list > > de...@open-mpi.org > > http://www.open-mpi.org/mailman/listinfo.cgi/devel > > > > -- > Jeff Squyres > Cisco Systems > > > _______________________________________________ > devel mailing list > de...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/devel >
