We debugged this in private emails with Hartmut. His 48-core platform is
now detected properly. Everything got fixed with a patch
functionnally-identical to what Samuel sent earlier. There's a bit of
work before we can commit the fix, but Windows support for more than 32
cores will be officially fixed in the upcoming hwloc v1.4.2.
Thanks a lot to Hartmut for testing all these patches.