Parallel tasks are limited to 1 core per host
We have found a counter-intuitive behavior in parallel tasks in current SG (tried with latest release 3.23.2).
We expected that repeating a host meant that several cores of the host would be used, but that is not the case.
It seems that only one core can be used for each host in the ptask.
MWE
mwe.cpp platform.xml Makefile default.nix
The attached MWE computes the same computation-only ptask on different host allocations.
make && ./mwe ./platform.xml # or nix-build
Execution log
[monocore:test:(1) 10.000000] [mwe/INFO] Computed on two different hosts. Took 10 s
[monocore:test:(1) 30.000000] [mwe/INFO] Computed on one 1-core host. Took 20 s
[monocore:test:(1) 50.000000] [mwe/INFO] Computed on one 2-core host. Took 20 s
Expected behavior
Computed on two different hosts. Took 10 s
Computed on one 1-core host. Took 20 s
Computed on one 2-core host. Took 10 s <-------------------------------------