Todd Gamblin 501cb371c9 concretizer: handle variant defaults with optimization ... - Instead of using default logic, handle variant defaults by minimizing the number of non-default variants in the solution. - This actually seems to be pretty fast, and it fixes the long-standing issue that writing this: spack install hdf5 ^mpich will fail if you don't specify hdf5+mpi. With optimization and allowing enums to be enumerated, the solver seems to be able to quickly discover that +mpi is the only way hdf5 can depend on mpich, and it forces the switch to be thrown.		2020-11-17 10:04:13 -08:00
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spack	concretizer: handle variant defaults with optimization	2020-11-17 10:04:13 -08:00