---
title: "Magma V2.18-6 Patch Notes"
canonical: "https://docs.magma-maths.org/patchnotes/2.18-6.html"
source: "https://docs.magma-maths.org/patchnotes/2.18-6.md"
---

<a id="magma-v2-18-6-patch-notes"></a>
# Magma V2.18-6 Patch Notes

## Aggregates

- A crash in [`Xor`](../SetsSequencesMappings/Sequences/operation.md#function-xor-boolelt-boolelt) when one of the sequences is null has been fixed.
- Multiset hashing was returning invalid values for certain underlying types, such as vectors.  This has been fixed. Reported by M. Kiermaier.

## Arithmetic Geometry

- Changed `IsLocallySolvable` to not use coproducts when valuations are Infinity(). This works around bugs that were occurring.

## Elliptic Curves

- The elliptic curve database of all curves of small conductor has been updated to reflect a recent change of numbering of 98 curves. Requested by J. Cremona.
- [`MordellWeilShaInformation`](../ArithmeticGeometry/EllipticCurvesOverQAndNumberFields/mordell-weil.md#function-mwsiref) now additionally uses 8-descent, where necessary.
- An infinite loop occuring occasionally in [`pAdicEllipticLogarithm`](../ArithmeticGeometry/EllipticCurvesOverQAndNumberFields/intro-2.md#function-padicellipticlogarithm-ptell-rngintelt) (and in `IntegralPoints`) has been fixed.
- The intrinsic [`QuarticReduce`](../ArithmeticGeometry/EllipticCurvesOverQAndNumberFields/mordell-weil.md#function-quarticreduce-rngupolelt) (used in descent) has been patched to avoid an infinite loop with $-6x^4 + 12x^3 - 7x^2 + x$.

## Extended Reals

- Fixed a possible crash when using extended reals. Reported by M. Kirschmer.

## Function Fields

- An internal embedding computation in computing a Galois group of a polynomial over a global rational function field has been corrected.
- A bug has been fixed in `OptimizedRepresentation`.

## Groebner Bases

- An error arising from non-reduced Groebner bases over finite fields of characteristic 2 has been fixed.  Reported by M. Stoll.

## Groups

- A bug computing the automorphism group of a matrix has been fixed. There were cases where the group found was not the whole automorphism group. Reported by M. Grassl.
- A number of problems when computing the `SubgroupLattice` of a matrix group have been corrected. Reported by Y. Edel.

## Hilbert Modular Forms

- `NewSubspace` had been accidentally disabled, for spaces of higher weight; it is now available again.

## Local Fields

- Fixed a typo in Magma-level printing of extensions of a p-adic field. Reported by T. Dokchitser.

## Matrices

- An infinite recursion problem in `SmithForm` for matrices having very small rank has been fixed.  Reported by D. Yasaki.
- A crash involving very large integer matrices has been fixed.  Reported by D. Yasaki.

## Number Fields

- Fixed a bug with incompatible sequence elements in `SplittingField`. Reported (and a fix provided) by A. Elkin.

## Polytopes

- `DatabaseID` now returns the database ID of a canonical Fano 3-tope. This requires the most recent version of the `canonical3` database (updated 29th March).
- Added `PolytopeSmallPolygon` for accessing the `smallpolygons` database. This database lists all polygons, up to translation and change of basis, that fit inside a [0,7] x [0,7] box.
- `Points` is significantly faster in the case of reflexive polytopes.
- `MinkowskiDecomposition` and `LatticeMinkowskiDecomposition` now work for lattice polytopes of arbitrary dimension.

## Quadratic Fields

- The preimage of a sequence under a map from a class group into the set of ideals of a maximal order has been fixed.

## Ray Class Groups

- `RayClassGroup` now checks whether its input is a zero ideal. Reported by T. Dokchitser.