use config (i.e. freeze) constraints also as solver version prefs #7491
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As in #7490, I think that preferences shouldn't have a significant effect on performance if there are already constraints on the same choices, since the constraints should be enforced at the time that the choices are made. The solver also creates log messages about versions that were rejected by constraints by traversing those versions' nodes. |
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As discussed here and on the appropriate tickets it seems like this doesn't really do something useful, so closing for now. |
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Do we leave the branch there? |
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IMHO the users may want to test if this one brings any improvements, if they still yearn for more or their scenario changes. But maybe I'm cargo-culting: gbaz==speed. |
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This extends version prefs handed to the solver (to guide it) by any version constraints fixed directly in a project config (or freeze) file. It cuts down the number of local backjumps, because the prefs are applied before directly traversing the version tree. This was done to see if it could improve the situation in #7466 but my tests don't seem to show a significant speedup -- i.e. local backjumps appear cheap, similar to #7490 .
So I'm not sure if there's any significant benefit in ensuring preferences are applied before running the solver and just letting the constraint conflict machinery immediately apply the fixed version constraints from the freeze file. Again interested in feedback from the Usual solver experts (@dcoutts @grayjay @ezyang and anyone else I may not have thought of here).