Interactive Environment and Processing

The interactive limit (CPU time) per login session on all systems is 1 hour and you may only use up to 4 processors during a login. A user is expected to lower this limit under heavy system loads. This limitation can be overcome by using the batch system (See section on Batch Processing).

PROCESSOR LIMIT IS 4 FOR INTERACTIVE USE

As mentioned in the Basic System Information section, there are two nodes, f1n1 (IP name= hydra) and f1n10 (IP name= hydra2), dedicated to login, and interactive processing that is outside the control of the Load Leveller (LL), IBM's batch facility. In doing test runs, therefore, with OpenMP or MPI programs please do not exceed the concurrent use of four processors. Interactive use should be limited to developing and testing for the small scale. For that reason, do become familiar with batch processing as early as possible. For an expanded interactive capability, see the discussion on the Interactive Queue in the section for batch processing.

You may view your login session limits with the ulimit -a command. The output below shows the typical output of the ulimit command for the ksh shell, the default interactive shell on hydra.

hydra# ulimit -a time(seconds) 3600 file(blocks) unlimited data(kbytes) 1572864 stack(kbytes) 1048576 memory(kbytes) 1572864 coredump(blocks) 2097151 nofiles(descriptors) 2000

The default shell for hydra is ksh. This shell is recommended for batch processing. You must NOT copy startup files from other systems to your home directory on hydra.

The TMPDIR environment variable specifies a directory where temporary files should be placed. The default location for TMPDIR is /scratch/$USER/tmp for interactive sessions. Applications which use the TMPDIR variable will place temporary files created during execution in the TMPDIR directory. It should be emphasized that the TMPDIR of an interactive session is completely different from the TMPDIR in a batch job. The latter exists only during a job's tenure in the system.

In general, the environments for applications, compilers, libraries are managed with modules.

Viewing Man Pages

Information can be found for almost any command in the command's online manual (commonly referred to a man page) page. The following shows how to view the man page for the ls command.

hydra% man ls

We provide the following files in your home directory upon account creation.