Hi, When running NAS parallel benchmarks using 4 Raspberry Pi nodes each running MPICH-3.1.2 I get the following error when I try to run the integer sort benchmark ~/NPB3.3/NPB3.3-MPI/bin $ mpiexec -n 4 -machinefile /home/pi/mpi_testing/machinefile ./is.S.4 NAS Parallel Benchmarks 3.3 -- IS Benchmark Size: 65536 (class S) Iterations: 10 Number of processes: 1 ERROR: compiled for 4 processes Number of active processes: 1 Exiting program! ./is.S.4: error while loading shared libraries: libmpi.so.12: cannot open shared object file: No such file or directory ./is.S.4: error while loading shared libraries: libmpi.so.12: cannot open shared object file: No such file or directory ./is.S.4: error while loading shared libraries: libmpi.so.12: cannot open shared object file: No such file or directory I have tried export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/rpimpi/mpich3-install/lib on each of the nodes, and each node works individually when run with the file ./is.S.1 $ldd ./is.S.4 give the following output for the master node /usr/lib/arm-linux-gnueabihf/libcofi_rpi.so (0xb6edf000) libmpi.so.12 => /home/rpimpi/mpich3-install/lib/libmpi.so.12 (0xb6ca3000) libc.so.6 => /lib/arm-linux-gnueabihf/libc.so.6 (0xb6b68000) librt.so.1 => /lib/arm-linux-gnueabihf/librt.so.1 (0xb6b59000) libpthread.so.0 => /lib/arm-linux-gnueabihf/libpthread.so.0 (0xb6b3a000) libgfortran.so.3 => /usr/lib/arm-linux-gnueabihf/libgfortran.so.3 (0xb6a93000) libm.so.6 => /lib/arm-linux-gnueabihf/libm.so.6 (0xb6a22000) libgcc_s.so.1 => /lib/arm-linux-gnueabihf/libgcc_s.so.1 (0xb69fa000) /lib/ld-linux-armhf.so.3 (0xb6eed000) please help Thanks Sophie