On Wed, 2010-07-28 at 11:48 -0400, Gus Correa wrote: > Hi Hugo, Jeff, list > > Hugo: I think David Zhang's suggestion was to use > MPI_REAL8 not MPI_REAL, instead of MPI_DOUBLE_PRECISION in your > MPI_Allreduce call. > > Still, to me it looks like OpenMPI is making double precision 4-byte > long, which shorter than I expected it be (8 bytes), > at least when looking at the output of ompi_info --all. > > I always get get a size 4 for dbl prec in my x86_64 machine, > from ompi_info --all. > I confirmed this in six builds of OpenMPI 1.4.2: gcc+gfortran, > gcc+pgf90, gcc+ifort, icc+ifort, pgcc+pgf90, and opencc+openf95. > Although the output of ompi_info never says this is actually the size > of MPI_DOUBLE_PRECISION, just of "dbl prec", which is a bit ambiguous. > > FWIW, I include the output below. Note that alignment for gcc+ifort > is 1, all others are 4. > > Jeff: Is this correct?
This is wrong, it should be 8 and alignement should be 8 even for intel. And i also see exactly the same thing. -- Ake Sandgren, HPC2N, Umea University, S-90187 Umea, Sweden Internet: a...@hpc2n.umu.se Phone: +46 90 7866134 Fax: +46 90 7866126 Mobile: +46 70 7716134 WWW: http://www.hpc2n.umu.se
