--- title: "Magma V2.28-18 Patch Notes" canonical: "https://docs.magma-maths.org/patchnotes/2.28-18.html" source: "https://docs.magma-maths.org/patchnotes/2.28-18.md" --- # Magma V2.28-18 Patch Notes ## Algebraic Number Fields - Recomputation of maximal orders using the Montes Algorithm has been avoided for example, when computing `ClassGroup`. Reported by Noam D. Elkies. - The decision on which Maximal order algorithm to use for number fields has been made more reliable. Reported by Noam D. Elkies. ## Algebras - `Center` is no longer available for `AlgInfD` unless the algebra also inherits from `Rng`. This removes the Ambiguous Signature match which was occurring. Reported by Csaba Schneider. ## Associative Algebras - For an algebra of type `AlgAssV` the intrinsic `WriteOver` is not the inverse of `RepresentationMatrixOfMatrix`. Indeed, if `M := RepresentationMatrixOfMatrix([a])`, then `WriteOver(M,A)` returns a, not [a]. Therefore, instances of `WriteOver` in the intrinsics `ConjugacyClasses`, `CharacterTable`, `IsConjugate` and `InvariantForms` in the file Hermitian/automorphisms.m have been changed to `WriteOverMatrix`. ## Groups - A crash using `Extension` with `GrpPerm` argument when the underlying group of the cohomology module is not a permutation or matrix group has been trapped to give a runtime error with a more useful error message. Bug reported by Steve Humphries. - The operator `subset` has been improved for PC groups to avoid a blowup in memory and time usage when applied to the same group many times. Issue reported by Derek Holt. - A crash in `IsConjugate` called on subgroups of a quaternionic matrix group has been fixed. The problem was in computing the orbit of a 1-dimensional subspace of the natural `RSpace` of the group, so any problems with such computations should now be trouble free. Bug reported by Don Taylor. ## Lattices - A bug in `SuccessiveMinima` where the lattice basis had wide ranging bit lengths has been fixed. Reported by Wouter Castryck. ## Local Rings - A fix has been made to [`AllExtensions`](../LocalFields/PAdicRingsAndTheirExtensions/extensions.md#function-allextensions-rngpad-rngintelt) when the degree of the extensions is divisible by the prime of the input ring. Reported by Nuno Freitas. ## Modular Forms - A crash in `HeilbronnMerel(N)` for large $N$ (coming out of a call to `HeckeOperator`) has been fixed. Reported by Drew Sutherland. ## Representation Theory - An error in `IrreducibleModules` when running in the Magma Calculator has been fixed. Reported by Dikran Karagueuzian. ## Schemes - The function `ProjectiveSpace` has been fixed in the case that a grading is given, so that the `grevlexw` monomial order is now used with that grading to define the underlying polynomial ring. This means that underlying Groebner bases are often smaller and more quickly computed than previously. In particular, [`JacobianSubrankScheme`](../AlgebraicGeometry/Schemes/schemes-global.md#function-jacobiansubrankscheme-sch) is much faster for some types of input involving graded spaces. Example input provided by Muhammad Imran Qureshi. ## System - A flag has been added to warn when a new package intrinsic overrides an older intrinsic; the corresponding set/get intrinsics are [`SetWarnIntrinsicOverride`](../MagmaLanguage/EnvironmentAndOptions/Set-Get.md#function-setwarnintrinsicoverride-boolelt) and [`GetWarnIntrinsicOverride`](../MagmaLanguage/EnvironmentAndOptions/Set-Get.md#function-getwarnintrinsicoverride). Currently it defaults to false (no warning). The warning message when overriding an intrinsic now prints the extended types of the intrinsic arguments where appropriate. - `HasSignature` no longer crashes when the intrinsic has signatures using tilde parameters.