Gaussian shared memory

If you are running Gaussian in shared memory mode (in parallel in a multi-CPU computer, for example), you might get the following error (last line of output file):

shmget failed

It means that it was not possible to get the amount of shared memory required by the input. This can mean that the computer does not have so much physical RAM, but usually it is just a somewhat silly system setting.

Check the file /proc/sys/kernel/shmmax. Inside it there should be a single number, namely the amount of permited shared memory use (in bytes). If you need more (in my computer it was like 32MB… puaff), just echo xxx > /proc/sys/kernel/shmmax, where xxx is the desired amount of bytes (e.g. 500000000).