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Performance Tuning NWChem

NWChem ( is known to have I/O performance issues, in particular when run on a network file system (such as GPFS or NFS).

The pattern of I/O seems to be to write a number of (small) files, and then re-read them repeatedly. It appears to be the repeated reading of these small files which causes an I/O bottleneck on our GPFS network file system.

We have found that setting NWChem to use a local scratch disk greatly improved the I/O performance, and the overall performance of NWChem. The setting is as follows:

scratch_dir /tmp

Other performance tips can be found here: