A.5 I’m running a calculation for a large system, and it exits abrutply. What’s going on?

It is possible that you are indeed running out of memory. See the next section, “What do I do if I run out of memory?”

However, do check if you really did set “ulimit -s unlimited” before running the calculation. If FHI-aims is compiled with an additional C compiler (this is as simple as defining the “CC” environment variable in make.sys or in the Makefile), then FHI-aims’ standard output also writes the stack size that is set for each MPI task. Sometimes the result can be surprising – for example, some MPI libraries’ mpirun command does not propagate the stack size limit to all compute nodes.