core: change code path when using one hash group

Link: https://github.com/GeneAssembly/biosal/issues/720
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
thorium: add compute-to-communication ratio in actor profiles

Link: https://github.com/GeneAssembly/biosal/issues/720
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>