I am observing differences in floating-point results from an application
program that appear to be related to whether I link with OpenMPI 1.4.3 or
MVAPICH 1.2.0. Both packages were built with the same installation of Intel
11.1, as well as the application program; identical flags passed to the
compiler in each case.
I've tracked down some differences in a compute-only routine where I've printed
out the inputs to the routine (to 18 digits) ; the inputs are identical. The
output numbers are different in the 16th place (perhaps a few in the 15th
place). These differences only show up for optimized code, not for -O0.
My assumption is that some optimized math intrinsic is being replaced
dynamically, but I do not know how to confirm this. Anyone have guidance to
offer? Or similar experience?
Thanks very much
Ed
Just for what it's worth, here's the output of ldd:
% ldd application_mvapich
linux-vdso.so.1 => (0x00007fffe3746000)
libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x00002b5b45fc1000)
libmpich.so.1.0 =>
/usr/mpi/intel/mvapich-1.2.0/lib/shared/libmpich.so.1.0 (0x00002b5b462cd000)
libibverbs.so.1 => /usr/lib64/libibverbs.so.1 (0x00002b5b465ed000)
libibumad.so.3 => /usr/lib64/libibumad.so.3 (0x00002b5b467fc000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00002b5b46a04000)
librt.so.1 => /lib64/librt.so.1 (0x00002b5b46c21000)
libm.so.6 => /lib64/libm.so.6 (0x00002b5b46e2a000)
libdl.so.2 => /lib64/libdl.so.2 (0x00002b5b47081000)
libc.so.6 => /lib64/libc.so.6 (0x00002b5b47285000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00002b5b475e3000)
/lib64/ld-linux-x86-64.so.2 (0x00002b5b45da0000)
libimf.so => /opt/intel/Compiler/11.1/072/lib/intel64/libimf.so
(0x00002b5b477fb000)
libsvml.so => /opt/intel/Compiler/11.1/072/lib/intel64/libsvml.so
(0x00002b5b47b8f000)
libintlc.so.5 => /opt/intel/Compiler/11.1/072/lib/intel64/libintlc.so.5
(0x00002b5b47da5000)
% ldd application_openmpi
linux-vdso.so.1 => (0x00007fff6ebff000)
libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x00002b6e7c17d000)
libmpi_f90.so.0 => /usr/mpi/intel/openmpi-1.4.3/lib64/libmpi_f90.so.0
(0x00002b6e7c489000)
libmpi_f77.so.0 => /usr/mpi/intel/openmpi-1.4.3/lib64/libmpi_f77.so.0
(0x00002b6e7c68d000)
libmpi.so.0 => /usr/mpi/intel/openmpi-1.4.3/lib64/libmpi.so.0
(0x00002b6e7c8ca000)
libopen-rte.so.0 => /usr/mpi/intel/openmpi-1.4.3/lib64/libopen-rte.so.0
(0x00002b6e7cb9c000)
libopen-pal.so.0 => /usr/mpi/intel/openmpi-1.4.3/lib64/libopen-pal.so.0
(0x00002b6e7ce01000)
libdl.so.2 => /lib64/libdl.so.2 (0x00002b6e7d077000)
libnsl.so.1 => /lib64/libnsl.so.1 (0x00002b6e7d27c000)
libutil.so.1 => /lib64/libutil.so.1 (0x00002b6e7d494000)
libm.so.6 => /lib64/libm.so.6 (0x00002b6e7d697000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00002b6e7d8ee000)
libc.so.6 => /lib64/libc.so.6 (0x00002b6e7db0b000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00002b6e7de69000)
/lib64/ld-linux-x86-64.so.2 (0x00002b6e7bf5c000)
libifport.so.5 =>
/opt/intel/Compiler/11.1/072/lib/intel64/libifport.so.5 (0x00002b6e7e081000)
libifcoremt.so.5 =>
/opt/intel/Compiler/11.1/072/lib/intel64/libifcoremt.so.5 (0x00002b6e7e1ba000)
libimf.so => /opt/intel/Compiler/11.1/072/lib/intel64/libimf.so
(0x00002b6e7e45f000)
libsvml.so => /opt/intel/Compiler/11.1/072/lib/intel64/libsvml.so
(0x00002b6e7e7f4000)
libintlc.so.5 => /opt/intel/Compiler/11.1/072/lib/intel64/libintlc.so.5
(0x00002b6e7ea0a000)
