[petsc-users] Does an optimized compilation with -march=native on multi-CPU HPC cluster make sense?

[Bastian Löhrer]

Dear PETSc users,

we use PETSc in our code.
Therefore, we have multiple PETSc compilations lying around, each 
compiled differently,
e.g debug build using an Intel-compiler, optimized build for Intel-CPUs 
using an Intel-compiler, optimized build for AMD-Rome-CPUs using an 
Intel-compiler, several builds using GNU-compilers ...

Prior to compiling our code, we essentially set $PETSC_DIR and 
$PETSC_ARCH to point to a suitable PETSc build.

When I compile such an optimized PETSc build aimed at Intel-CPUs and 
using an Intel-compiler I do so with

     COPTFLAGS="-axCOMMON-AVX512,CORE-AVX2,AVX ..."

to address all Intel processors available on our cluster.

However, I recently noticed that the PETSc compilation provided by our 
HPC-administrators was compiled with -march=native.
Does that make sense? If so this implies that my optimization flags are 
unnecessary, does it not?

I imagine that when using a PETSc previously compiled with march=native 
and I compile that into my code on a CPU different from the one that has 
been used when compiling PETSc, I end up without optimizations of PETSc. 
Is that correct?

Best,
Bastian