Performance Tuning NWChem
NWChem (http://www.emsl.pnl.gov/root/capabilities/computing/nwchem/download/) 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:
Other performance tips can be found here: http://rcc.its.psu.edu/hpc/software/nwchem/