--- title: "Magma V2.18-8 Patch Notes" canonical: "https://docs.magma-maths.org/patchnotes/2.18-8.html" source: "https://docs.magma-maths.org/patchnotes/2.18-8.md" --- # Magma V2.18-8 Patch Notes ## Admissible Representations - When creating a [`LocalComponent`](../ModularArithmeticGeometry/RepresentationsOfLocalFields/creation.md#function-localcomponent-modsym-rngintelt), there is now an option to set `CheckMinimal` to false: in this case, the input will be assumed to be minimal, skipping the potentially expensive check. ## Aggregates - A crash associated with use of coproducts has been fixed. Reported by E. O’Brien as a crash in [`CompositionTree`](../FiniteGroups/MatrixGroupsOverFiniteFields/composition-tree.md#function-compositiontree-grpmat-fldfin). - A bug in associative arrays that could cause crashes when keys of different universes are used has been fixed. ## Algebraic Function Fields - A fix has been made to memory management in the computation of `MaximalOrder`s in Artin-Schreier extensions. - Computations involving kernels of matrices over function fields whose constant field is not a finite field or the rationals have been fixed. ## Algebraic Number Fields - A fix has been made to memory management in the computation of roots of elements in number fields. - The torsion unit computation has been fixed. - A fix has been made to memory management in a part of the `ClassGroup` and `UnitGroup` computations where the class group is computed using the Sieving algorithm. - A fix has been made to computations of polynomial GCDs over fields of fractions of non-equation orders when the subresultant algorithm was used. Reported by N. Bruin. - The computation of `Subfields` using the Klüners-van Hoeij algorithm has been improved in the areas of the prime selection and gradual LLL_with_removals computations. The choice between the Klüners-van Hoeij algorithm and the Klüners algorithm has also been improved. - Testing a large ideal of a non-maximal order for being principal has been fixed. - A fix has been made to `AbsoluteOrder`. - A leak has been fixed in `Factorization` of elements of quadratic fields. Reported by R. Broker. ## Binary Quadratic Forms - The commands `PicardGroup` for quadratic nonmaximal orders and `ClassGroup` for quadratic forms for nonfundamental discriminants had been returning incorrect answers for some time. This has been corrected. Reported by John Voight. ## Class Field Theory - A fix has been made to the computation of a `MaximalOrder` for fields constructed as (ray) class fields. Reported by D. Mayer. ## Coding Theory - A bug in `AutomorphismGroup` for codes over non-binary finite fields would cause the computation to be done over the *less* efficient choice out of the code and its dual. This bug has been fixed. Reported by M. Grassl. ## Commutative Algebra - A bug in [`RegularSequence`](../CommutativeAlgebra/PolynomialRingIdealOperations/ideal-operation.md#function-regularsequence-rngmpol) has been fixed. Reported by Claude Quitte. - A bug in [`Homogenization`](../CommutativeAlgebra/PolynomialRingIdealOperations/homogenization.md#function-homogenization-rngmpol-rngintelt-boolelt) has been fixed. Reported by Damiano Testa and Tony Varilly-Alvarado. ## Cones and Polyhedra - Fixed a potential crash when taking -P of a polyhedron P. Reported by T. Coates. - Added `Representative` for a cone C, so correcting unexpected behaviour. Reported by T. Coates. ## Curves - The restriction that the degree of the place input to `Expand` is 1 has been removed (now consistent with `Expand` taking a place of an algebraic function field). Reported by M. Grassl. - `Completion` of a function field of a curve at a place is now directly available. ## Cyclotomic Fields - Coercion between Cyclotomic fields when only one of the fields has sparse representation has been fixed. ## Elliptic Curves - A bug in the elliptic curve rank computation (for elliptic curves defined over the rational field) has been fixed; this bug could cause some covering curves to be erroneously discarded as not contributing to the 2-Selmer group, and thus may under-report the upper bound on the rank or fail with a warning about a missing quartic. This bug does not affect curves with rational 2-torsion. Reported by E. Rains. - A bug in the elliptic curve Chabauty routine has been fixed. Reported by Enrique Gonzalez-Jimenez. - The elliptic curve database now includes all curves of conductor up to 240,000. ## Groebner Bases - A crashes in computing Groebner bases for ideals over number fields has been fixed. Reported by T. Fisher. - A bug in [`EasyBasis`](../CommutativeAlgebra/GrobnerBases/groebner.md#function-easybasis) that was occasionally producing incorrect results has been fixed. ## Groups - A crash in the `CharacterTable` function has been fixed. Reported by E. O’Brien. - The stored name for [`PrimitiveGroup`](../FiniteGroups/DatabasesOfGroups/primgp-data.md#function-primitivegroup-rngintelt-rngintelt)(64, 41) has been changed to 2^6:PGL(2,7). (It was 2^6:GL(3,2), which is half the order of the stored group.) Reported by J. Schmidt. - A bug in [`RecogniseClassical`](../FiniteGroups/AlmostSimpleGroups/group-recognition.md#function-recogniseclassical-grpmat) has been fixed. A non-classical group was incorrectly identified as Omega(3, 9). Fix provided by Alice Niemeyer. ## Incidence Geometry - A new function is included for coset geometries. Dimitri Leemans has supplied a [`LocallySArcTransitive`](../Geometry/IncidenceGeometry/primitivityproperties.md#function-locallysarctransitive-cosetgeom) function. This returns the largest integer s such that the given coset geometry is locally s-arc-transitive but not locally (s+1)-arc-transitive. ## LSeries - Taking the `TensorProduct` now always gives a `Conductor` that is a `RngIntElt` – previously it could occasionally be a `FldRatElt`, which could later cause problems. ## Modular Curves - An bug has been fixed in the `Isogeny` and `SubgroupScheme` intrinsics which produced incorrect results for input elliptic curves not of the form $y^2=x^3+Ax+B$. ## Modular Forms - Runtime errors occuring for weight one forms have been fixed. Reported by David Loeffler and others. - A runtime error in [`Newforms(I, M)`](../ModularArithmeticGeometry/ModularForms/newforms.md#function-newforms-modfrm) has been fixed. Reported by Kartik Prasanna. - `IsTwist` and [`IsMinimalTwist`](../ModularArithmeticGeometry/ModularSymbols/twists.md#function-isminimaltwist-modsym-rngintelt) now use sharp bounds (as in Loeffler-Weinstein), making them massively faster. Since V2.18 very crude bounds had been used, and prior to V2.18 there were occasional errors. ## Schemes - A problem in [`IsNode`](../AlgebraicGeometry/AlgebraicCurves/local-curve.md#function-isnode-pt) and [`TangentCone`](../AlgebraicGeometry/AlgebraicCurves/local-curve.md#function-tangentcone-pt) has been fixed that was causing a large slowdown in some cases by inefficient translation to the origin. Reported by Pietro Mercuri and David Kohel. ## Series Rings - When evaluating a power series at another power series, the precision of the result could have been set lower than it should be. This has now been fixed.