On Jun 20, 2012, at 3:36 PM, Martin Siegert wrote: > by now we know of three programs - dirac, wrf, quantum espresso - that > all hang with openmpi-1.4.x (have not yet checked with openmpi-1.6). > All of these programs run to completion with the mpiexec commandline > argument: --mca btl_openib_flags 305 > We now set this in the global configuration file openmpi-mca-params.conf. > What is the reason that this is not the default in the first place? > Are there any negative effects?
Two things: 1. These flags -- 305 (or 0x131 or 0001 0011 0001) translate to telling the openib BTL the following: - 1: SEND: meaning that the openib BTL is using send/receive semantics - 16: ACK: meaningless with the ob1 PML - 32: CHECKSUM: meaningless with the ob1 PML - 256: meaningless What's meaning here is what is missing: RDMA PUT and GET. So all RDMA support is disabled. This will work fine, but you may want to increase your mca_btl_openib_eager_limit size (e.g., U. Michigan did the same thing as you -- disabled RDMA -- but increased the eager limit to 64k to get back some of the lost performance). 2. We believe that we have *finally* (just recently) fixed this issue in the SVN trunk and upcoming 1.6.1 release. I have a test pre-release 1.6.1 tarball -- would you mind giving it a whirl? http://www.open-mpi.org/~jsquyres/unofficial/openmpi-1.6.1ticket3131r26612M.tar.bz2 -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
