NWChem Frequently Asked Questions

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# NWChem FAQ ### Linux Clusters What hardware configuration is suggested for running NWChem on Linux cluster? How do I install and run NWChem on Myrinet clusters? How do I install NWChem on Giganet clusters? How do I increase the shared memory segment in FreeBSD? What hardware configuration is suggested for running NWChem on Linux cluster? Most of the NWChem modules are not going to perform well on large Linux clusters that use just Fast Ethernet for communication. For optimal performance, you need to use either Giganet or Myrinet interconnects. How do I install and run NWChem on Myrinet clusters? Prior to installing NWChem, you must have installed the GM and the MPICH over GM softwares on the system. Before starting the NWChem compilation, the following environmental variables must be defined
    USE_MPI=y
    GM_HOME="location of GM software"
    GM_INCLUDE=$GM_HOME/include
    GM_LIB=$GM_HOME/lib
    ARMCI_NETWORK=GM
    MPI_LOC="location of MPICH-GM software"
    MPI_LIB=$MPI_LOC/lib
    MPI_INCLUDE=$MPI_LOC/include
    LIBMPI=-lmpich
To run NWChem, you need to set the following enviromental variable
    GMPI_SHMEM_FILE /tmp/$USER.gm
The next step is to launch the program. One way to do it is by using the mpirun.ch_gm script supplied in the MPICH-GM tar file. The command to execute is
    mpirun.ch_gm --gm-use-shmem $NWCHEM_TOP/bin/LINUX/nwchem
or
    mpiexec $NWCHEM_TOP/bin/LINUX/nwchem
How do I install NWChem on Giganet clusters? Before starting the NWChem compilation, the following environmental variables must be defined
    ARMCI_NETWORK=VIA
    LIBMPI="-lmpipro -lpthread"
To run NWChem, you need to set the following environmental variable
    MPI_COMM=VIA
How do I increase the shared memory segment in FreeBSD? To increase the shared memory segments on FreeBSD the following two sysctl's should be added to the startup scripts (e.g. /etc/rc.local):
    sysctl -w kern.ipc.shmmax=67108864
    sysctl -w kern.ipc.shmall=16384
the first sysctl allocates 64Mbytes of memory, the second does the same thing in 4k pages (4k * 16384 = 64M), you must set both sysctl. NWChem | Capabilities | Platforms | Download | User's Manual | Programmer's Manual | Release Notes | FAQ Known Bugs | Support | Tutorial | Contributors | Benchmarks | Search | Mol Sci. Soft. Group | Citation Contact: NWChem Support Updated: February 22, 2005