G4 Cluster User Guide

The G4 cluster is available for general use by members of the SCL and partnering groups. Access to other groups is determined on a case by case basis. The PPC cluster is designed in part for CS code development so queue time limits are set to 2 days and may be reduced when fast turnaround is needed.

Logging on

• You can connect to 4pack.scl.ameslab.gov via ssh from anywhere in the Scalable Computing Laboratory. Those wishing to have access to the cluster should fill out this form, sign it, and indicate that they wish to access 4pack. Existing SCL users can send email to help requesting access to 4pack.

  Once you are granted access your password is your normal SCL kerberos password. Within the cluster access to the nodes is performed via ssh using an ssh-key with a null passphrase.(ssh-keygen, then copy identity.pub into authorized_keys in your ~/.ssh directory).

Submitting jobs

• All jobs must be submitted through the batch system.
  Running jobs outside the batch system without permission is grounds for having your access to 4pack revoked.
• The GAMESS code is installed on 4pack. To submit GAMESS jobs use the "gms" command.

Compiling programs

• Along with the usual GNU compilers, there is a patched version of gcc available called gcc-vec that includes support for Motorola's Altivec C extensions.
• MPI programs can be compiled with the following compiler wrappers:
  • C: mpicc
  • C++: mpiCC
  • Fortran 77: mpif77
  • Fortran 90: mpif90
  Man pages are available for each of these wrappers. There are two versions of MPICH installed on 4pack to run MPI natively over Myrinet (MPICH-GM) and to use MPI over TCP either on Myrinet or Ethernet (MPICH-TCP). Both version are installed in /usr/local and you should add the desired versions bin directory to your path (e.g. for MPICH-gm add /usr/local/mpich-gm to your path).