--- title: "Magma V2.17-9 Patch Notes" canonical: "https://docs.magma-maths.org/patchnotes/2.17-9.html" source: "https://docs.magma-maths.org/patchnotes/2.17-9.md" --- # Magma V2.17-9 Patch Notes ## Admissible Representations - An underlying change to how `IsIrreducible` works when returning false caused various examples to break. The code here was changed to use `CompositionFactors` (of a G-module) instead. - A bug involving taking chi_p instead of 1/chi_p was fixed. ## Algebraic Function Fields - A fix has been made to `Expand` and the application of `Completion` maps. ## Algebras - The construction of sets of ideals of orders of associative algebras has been fixed. Reported by M. Kirschmer. - The testing of equality of homomorphisms between algebras which do not inherit from `AlgGen` has been fixed. ## Analytic Jacobians - A bug with [`IsIsomorphicSmallPeriodMatrices`](../ArithmeticGeometry/HyperellipticCurves/analytic.md#function-isisomorphicsmallperiodmatrices-mtrx-mtrx) was fixed. ## Coding Theory - A crash in [`ReedMullerCodeQRMZ4`](../CodingTheory/LinearCodesOverZ4/constructions.md#function-reedmullercodeqrmz4-rngintelt-rngintelt) has been fixed. Reported by M. Kiermaier. ## Coherent Sheaves - A bug in the code computing the maximal module of a sheaf has been fixed. This was causing errors in some cases in [`FullModule`](../AlgebraicGeometry/Sheaves/accessors.md#function-fullmodule-shfcoh) and the intrinsics depending on this, like [`IsLocallyFree`](../AlgebraicGeometry/Sheaves/shf:preds.md#function-shf-loc-free). Reported by Claude Quitte as an IsLocallyFree error applied to the tangent sheaf of a cubic surface. ## Commutative Algebra - An occasional incorrectness in the equality test for modules over euclidean rings has been fixed. Reported by C. Quitte. ## Global Arithmetic Fields - Removed stray timing printings from some Subfield calculations. ## Groups - A new version of the matrix group [`CompositionTree`](../FiniteGroups/MatrixGroupsOverFiniteFields/composition-tree.md#function-compositiontree-grpmat-fldfin) code has been installed. Code supplied by E. O’Brien. - A crash in `SolvableQuotient` has been fixed. Bug reported by S. Humphreys. - A bug in the creation of subgroups of pc-groups has been fixed. Bug reported by J. Klüners. - A crash when [`GenericAbelianGroup`](../FinitelyPresentedGroups/AbelianGroups/generic-abelian.md#function-genericabeliangroup) was given a non-structure argument now results in a runtime error. ## Hyperelliptic curves - `TwoSelmerGroup` for Jacobians of hyperelliptic curves of even degree other than 6 over the rationals had been disallowed, by mistake. In fact, `TwoDescent` is implemented for any degree (at least 4) over the rationals and over number fields, with certain provisos. - A bug in [`TwoCoverDescent`](../ArithmeticGeometry/HyperellipticCurves/two-selmer-set.md#function-twocoverdescent-crvhyp) (2-descent on curves) has been fixed; the precision in some local calculations is now increased as necessary. ## Lattices - A bug with computing the automorphism group of a lattice when the Gram matrix has entries over 2^30 has been fixed. Bug reported by G. Nebe. - A crash when computing the automorphism group of a lattice using the Vectors parameter to give the set of vectors to use has been fixed. - A crash in [`ShortVectorsProcess`](../LatticesQuadraticForms/Lattices/enumeration.md#function-shortvectorsprocess-lat-rngelt) for lattices over the reals with large entries has been fixed. Reported by I. Wagner. ## Lie Theory - Added an optional argument `Virtual` to the [`Branch`](../LieTheory/RepresentationsOfLieGroupsAndAlgebras/representation-properties.md#function-branchfrtovm) function, to allow computation of virtual decompositions of representations. - Fixed a bug in [`SimplyConnectedVersion`](../LieTheory/RootData/create-new-root-datum.md#function-simplyconnectedversion-rootdtm) (and [`AdjointVersion`](../LieTheory/RootData/create-new-root-datum.md#function-adjointversion-rootdtm)) that caused those functions to return incorrect results in case a non-semisimple root datum was given as input. This could subsequently cause a crash in other procedures, as reported by B. van Geemen. ## Linear Programming - A bug was fixed that could cause Magma to interface incorrectly with the linear programming package, which could result in incorrect solutions being returned. In particular, this affected integral problems solved by [`MaximalSolution`](../Optimization/LinearProgramming/instant-lp.md#function-maximalsolution-mtrx-mtrx-mtrx-mtrx), [`MinimalSolution`](../Optimization/LinearProgramming/instant-lp.md#function-minimalsolution-mtrx-mtrx-mtrx-mtrx), [`MaximalZeroOneSolution`](../Optimization/LinearProgramming/instant-lp.md#function-maximalzeroonesolution-mtrx-mtrx-mtrx-mtrx), and [`MinimalZeroOneSolution`](../Optimization/LinearProgramming/instant-lp.md#function-minimalzeroonesolution-mtrx-mtrx-mtrx-mtrx). ## Lists - Lists may now be tested for equality. - `Index` and `Position` are now defined for lists. ## Multisets - Magma level printing of a sequence of multisets has been fixed. - Calling [`Multisets`](../Combinatorics/EnumerativeCombinatorics/subsets.md#function-multisets-setenum-rngintelt) to get multisets of size one has been very slightly sped up. - Added a [`Multiset`](../LieTheory/RepresentationsOfLieGroupsAndAlgebras/representation-properties.md#function-multiset-lierepdec) intrinsic to produce a multiset from a sequence or set. ## Number Fields - Fix a problem in `Automorphisms` for non-simple fields. Reported by V. Busch. ## Polynomial Rings - A hang in multivariate factorization over finite fields has been fixed. Reported by A.-S. Elsenhans. ## Quadratic Fields - A fix has been made to the preimage computation of class group maps. ## Representation Theory - A crash in representations over quadratic orders has been fixed. Reported by A. Bartel. ## Topology - [`SimplicialComplex`](../Topology/SimplicialHomology/simplicial-complexes.md#function-simplicialcomplex-seqenum-setenum) now also allows a set of sets as its argument; this fixes a bug in [`AddSimplex`](../Topology/SimplicialHomology/simplicial-complexes.md#function-addsimplex-smpcpx-setenum). Reported by F. Lunnon.