Proposal to change optimization option of the default Fujitsu ARM64 compiler

Functionality to add/problem to solve

I'm trying to install by spack and run OpenFOAM on Supercomputer Fugaku by Fujitsu compiler. I would like to request a change in the default level of optimization, as I have experienced problems with side effects of optimization in Fugaku when running snappyHexMesh. (User reported snappyHexMesh going to endless loop.) Especially "-ffp-contract=fast" was particularly impactful. I would like to see the level lowered to the safer side.

wmake/rules/linuxARM64Fujitsu/c++Opt c++OPT = -ffp-contract=fast -ffast-math -O3 -funsafe-math-optimizations --> c++OPT = -O3

This may be related to this issue. #2537

Target audience

Fugaku Users

Proposal

I suggest lowering the optimization level. I have confirmed that it can be done with the -O3 option as following version.

OpenFOAM version: v2012, v2106, v2206 Fujitsu compiler version: 1.2.35