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Improve IrreducibleModules for permutation groups - #6832

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ThomasBreuer:TB_IrreducibleModules

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As far as I understand, the number of absolutely irreducible constituents of an irreducible module over a finite field is determined by the degree of the minimal field extension that is needed to split the module into absolutely irreducible constituents, see the comment in the code.
Thus one need not construct and decompose the module over the larger field.

(The MTX.IsAbsolutelyIrreducible call happens now inside MTX.DegreeFieldExt. Note that the old code did in fact construct the abs. irred. module over an even bigger field than is needed, since MTX.DegreeSplittingField means the degree over the prime field.)

As far as I understand, the number of absolutely irreducible constituents
of an irreducible module over a finite field is determined by the
degree of the minimal field extension that is needed to split the module
into absolutely irreducible constituents.
Thus one need not construct and decompose the module over the larger field.
@ThomasBreuer ThomasBreuer added kind: enhancement Label for issues suggesting enhancements; and for pull requests implementing enhancements topic: performance bugs or enhancements related to performance (improvements or regressions) release notes: not needed PRs introducing changes that are wholly irrelevant to the release notes topic: meataxe labels Nov 11, 2026
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ThomasBreuer marked this pull request as draft November 11, 2026 09:57
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(why is this a draft: another improvement should be added ...)

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kind: enhancement Label for issues suggesting enhancements; and for pull requests implementing enhancements release notes: not needed PRs introducing changes that are wholly irrelevant to the release notes topic: meataxe topic: performance bugs or enhancements related to performance (improvements or regressions)

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