f-exx-opt: Results are dependent on compiler/library versions and # of MPI ranks

[connoraird]

Description

In the branch f-exx-opt the Conquest_out results appear to be dependent on the compiler/libraries and the number of MPI ranks you use.

Compiler and library versions and their results

The results mentioned are for running the benchmark test_EXX_isol_C2H4_4proc_PBE0ERI_fullSZP_0.4_SCF

Mac, Apple ARM

On an M2 mac, the following Homebrew versions of each dependency were used.

fftw v3.3.10 scalapack v2.2.0_1 openblas v0.3.27 libxc v6.2.2 lapack v3.12.0 openmpi v5.0.3 gcc (gfortran) v14.1.0

With the above, the Harris-Foulkes energy obtained is, np-2, nt-1 - |* Harris-Foulkes energy = -13.443098419459020 Ha np-4, nt-1 - |* Harris-Foulkes energy = -14.028830939450383 Ha

Linux

On a UCL cluster (myriad) the following version were used.

fftw v3.3.8 scalapack v2.1.0 openblas v0.3.7 libxc v6.2.2 compiled myself with gcc v9.2.0 lapack from the above openblas openmpi v3.1.5 gcc (gfortran) v9.2.0

With the above, the Harris-Foulkes energy obtained was, np-2, nt-1 - |* Harris-Foulkes energy = -13.300253717139059Ha np-4, nt-1 - |* Harris-Foulkes energy = -13.561798008220549 Ha