Running a calculation in parallel

ORCA can run in multiple processors with the aid of OpenMPI (the recommended version for ORCA 6 is 4.1.6). After installing it and setting the PATH and LD_LIBRARY_PATH variables (what is that? Assigning PATH variables, you can simply run in parallel using the PAL keyword. For instance, a calculation using four processors requires:

!HF DEF2-SVP PAL4

For more than eight (!PAL8) or exactly 16 (!PAL16) processors, the explicit %PAL option has to be used:

!HF DEF2-SVP
%PAL NPROCS 28 END

When running calculations in parallel, always use the full path to ORCA:

./full/path/to/orca input.inp

Important

Always install the OpenMPI version indicated in the Download section!