--- title: "Magma V2.13-4 Patch Notes" canonical: "https://docs.magma-maths.org/patchnotes/2.13-4.html" source: "https://docs.magma-maths.org/patchnotes/2.13-4.md" --- # Magma V2.13-4 Patch Notes ## Algebraic Geometry - Extra functionality has been added to work with automorphism groups of curves. These groups are now returned as objects of a new type `GrpAutCrv` and individual automorphisms within these groups are constructed with type `GrpAutCrvElt`. As in the initial V2.13 release, the full group of automorphisms of a curve over the base field can be computed. In addition, the new structures allow the construction of subgroups of the full automorphism group and a range of additional functions for the groups and elements have been added. ## Algebraically Closed Fields - Algebraically closed fields may now be defined over finite fields and rational function fields over finite fields or the rationals (as well as the originally supported rational field). ## Arithmetic Geometry - A function [`HeightOnAmbient`](../AlgebraicGeometry/Schemes/anfs.md#function-heightonambient-pt) for calculating the height of a point on a general variety in projective or affine space has been added. - The function [`PointSearch`](../AlgebraicGeometry/Schemes/anfs.md#function-pointsearch-sch-fldrat-rngintelt) now works on varieties in affine spaces too. - There is now a type `ModelG1` for genus one models. ## Brandt Modules - A bug preventing certain Brandt modules from being created has now been fixed. ## Coding Theory - A memory leak in linear codes has been fixed. Reported by M. Grassl. - `MinimumDistance` no longer prints verbose output when the verbose flag is not set. Reported by M. Grassl. - `IsIsomorphic` is now the same as `IsEquivalent` for linear codes over fields. Request of Markus Grassl. ## Cohomology - Cocycles are now represented as functions taking a single argument which is a tuple of the appropriate size. ## Commutative Algebra - A bug in [`MinimalAlgebraGenerators`](../CommutativeAlgebra/InvariantTheory/minimalize-module.md#function-minimalalgebragenerators-rngmpol) with inhomogeneous input has been fixed. Reported by M. Grassl. - [`HomogeneousModuleTest`](../CommutativeAlgebra/InvariantTheory/minimalize-module.md#function-homogeneousmoduletest-rngmpol-rngmpol-rngmpol) has been fixed to handle zero polynomials. - A bug in polynomial factorization over number fields has been fixed. Reported by M. Grassl. - A bug that could cause a crash when taking GCDs of polynomials defined over polynomial quotient rings has been fixed. - Some memory leaks in integer polynomial divisibility testing were fixed. - Various fixes to the Galois group computation for polynomials. ## Elliptic Curves - The function [`CMPoints`](../ModularArithmeticGeometry/ArithmeticFuchsianGroupsAndShimuraCurves/triangle-groups.md#function-cmpoints-grppsl2-algassvordelt) now works also for non-fundamental discriminants (although the conductor of the quadratic order is still required to be coprime to the conductor of the elliptic curve). - `IntegralPoints` now has an optional parameter `Fast`, which only uses the new version of the routine. By default, both the new and old version are run, as a check. - The function `Saturation` for Mordell-Weil groups of elliptic curves has been improved so that it is useful on non-saturated examples, rather than only for proving that a set of points is saturated. - The `DivisionFunction` function now works and returns an element of the (geometric) function field of the curve rather than an element of the maximal finite order of its algebraic funxtion field. - A bug in the counting functions for supersingular elliptic curves over finite fields has been fixed. ## Finitely Presented Groups - [`SimpleQuotients`](../FinitelyPresentedGroups/FPGroups/quotient.md#function-grpfp-1-simplequotients)`(F, ord1, ord2)` added. ## Hyperelliptic Curves - A bug in `Points` for hyperelliptic Jacobians has been fixed (thanks to Michael Stoll). ## Integers - A potential infinite loop in the MPQS algorithm for integer factorisation has been removed. Reported by M. Grassl. - Calling `IsDivisibleBy` with a rational and a negative integer no longer crashes. ## Lattices - A bug introduced in V2.13-2 caused LLL to ignore the associated inner product of a lattice (if it had one). This has now been fixed. - Fixed a leak in lattice enumeration. Reported by D. Kohel. ## Lie Theory - The “classical” multiplication method for groups of Lie type has been improved enormously. - A bug in `StandardRepresentation` of groups of Lie type for type D1 has been fixed. - A bug in `StandardRepresentation` of groups of Lie type for types F4 and G2 has been fixed. Reported by A. Previtali. - A bug in Bruhat decomposition of negative root elements of groups of Lie type has been fixed. Reported by B. Späth. - A bug in `IsIsogenous` for groups of Lie type has been fixed. - The methods `SymbolicFromRight` and `CollectionFromRight` have been renamed back to `SymbolicToLeft` and `CollectionToLeft`. The `...FromRight` names were only used in 2.13-3. ## Maps - The `hom` constructor now handles length one sequences better. ## Matrices and Linear Algebra - Solution has been fixed to handle null sequence arguments. Some memory leaks were also fixed. - ChangeRing has been fixed to return an matrix space element if given one. Reported by M. Grassl. - Sundry bugs in the new LLL algorithm have been fixed. - More verbose information has been added for LLL. - The parameters to LLL are now listed in alphabetical order. - The computation of the determinant has been improved for dense matrices over certain Euclidean rings. - Functions `Pfaffian` and [`Pfaffians`](../MatricesLinearAlgebra/Matrices/properties.md#function-pfaffians-mtrx-rngintelt) have been added to compute the Pfaffian of a skew-symmetric matrix or the sequence of Pfaffians of principal submatrices of such a matrix. ## Matrix Groups - The error message when [`IsOverSmallerField`](../FiniteGroups/MatrixGroupsOverFiniteFields/aschbacher-reduction.md#function-isoversmallerfield-grpmat) is called on a reducible group has been improved. ## Number Fields - Bugs have been fixed in `IsMaximal` and `MaximalOrder` when non-monic defining polynomials were used. - Non-integral inputs are now longer allowed when creating an extension of an order. (i.e., via `ext``<RngOrd | ...>`.) ## Permutation Groups - A bug in the maximal subgroups machinery for permutation groups has been corrected. Originally, in the case of the group $PSp(4,7)$, $A_6$ was returned as a maximal subgroup, which it is not because it is contained in the maximal subgroup $A_7$. - `ASL`, `AGL`, etc. have been fixed to handle larger field sizes. ## Quaternion Algebras - A bug preventing certain quaternion orders from being created has now been fixed. - Several bugs in [`pMatrixRing`](../Algebras/QuaternionAlgebras/hilbert-symbols.md#function-pmatrixring-algquat-rngordidl) have been fixed, and the code has been optimised. - [`RightIdealClasses`](../Algebras/QuaternionAlgebras/ideal-theory.md#function-rightidealclasses-algquatord) now used the Eichler mass formula to determine when enumeration is complete. ## Rings and Fields - An error is now raised when attempting to construct a p-adic extension using a zero polynomial. ## System and Language - The maximum number of return values for an intrinsic package function has been increased from 5 to 256. - Setting the system memory limit to zero (no limit) no longer crashes.