Tell Sylow subgroups of natural An or Sn their size when we make them #529
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Add another pre-computed Size (centralizers) and fix a test.
stevelinton
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I have now checked gpprmsya.gi and there are no more obvious places where a Size was easily calculated but not set. |
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Looks good for merging |
hulpke
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Tell Sylow subgroups of natural An or Sn their size when they are created. This will save on a stab chain verification that can be costly for larger degrees.
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Saves a stab chain verification, which is relatively expensive. This removes the calculation being considered in #499 almost completely, but the issue there probably applies to many other stab chain verifications.
The same thing could probably be done in a lot of other methods in the same file, and possibly even more generally, although beware the issue we once had in GL where computing the order even using the formula took longer than writing down the group, just because of the integer arithmetic.
In this case the order was being computed anyway in the SylowSubgroup methods.