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Users can put a : in front of KMP_HW_SUBSET to indicate that the specified subset is an "absolute" subset. Currently, when a user puts KMP_HW_SUBSET=1t. This gets translated to KMP_HW_SUBSET="*s,*c,1t", where * means "use all of". If a user wants only one thread as the entire topology they can now do KMP_HW_SUBSET=:1t. Along with the absolute syntax is a fix for newer machines and making them easier to use with only the 3-level topology syntax. When a user puts KMP_HW_SUBSET=1s,4c,2t on a machine which actually has 4 layers, (say 1s,2m,3c,2t as the entire machine) the user gets an unexpected "too many resources asked" message because KMP_HW_SUBSET currently translates the "4c" value to mean 4 cores per module. To help users out, the runtime can assume that these newer layers, module in this case, should be ignored if they are not specified, but the topology should always take into account the sockets, cores, and threads layers.