---
title: "Magma V2.13-9 Patch Notes"
canonical: "https://docs.magma-maths.org/patchnotes/2.13-9.html"
source: "https://docs.magma-maths.org/patchnotes/2.13-9.md"
---

<a id="magma-v2-13-9-patch-notes"></a>
# Magma V2.13-9 Patch Notes

## Algebraic Curves

- An incorrect filename bug has been fixed in the `AutomorphismGroup` functions.

## Algebras

- A missing check in algebra coercion has been installed. Bug reported by M. Grassl.
- For quaternion algebras over number fields, the handling of real places has been fixed; the provious version would produce errors.

## Arithmetic Geometry

- Jacobians of hyperelliptic curves: bugs have been fixed in `TorsionSubgroup`, `TwoSelmerGroup` and `RankBounds`. Reported by A. Brumer.
- Elliptic curves over number fields: `TwoSelmerGroup` has been made more efficient in the case of largish degree number fields (because certain p-adic calculations can now be done using less precision).
- The constructor `EllipticCurve``(C,pt)` has had special cases added to deal with quadric intersections, and hyperelliptic curves in characteristic 2. The corrects a bug that arose when ZetaFunction was called for certain genus one curves over finite fields of characteristic 2.

## Coding Theory

- A bug in `meet` for $\mathbb{Z}_4$ codes has been fixed. Reported by G. Nebe.
- A bug which caused [`MinimumLeeWeight`](../CodingTheory/LinearCodesOverZ4/weight-distribution.md#function-minimumleeweight-code) to return incorrect results for $\mathbb{Z}_4$ codes having full rank has been fixed. Reported by N. Aydin.

## Groebner Bases

- A bug in the F4 algorithm when solving systems with 32 variables over $GF(2)$ has been fixed. Reported by Y. Seurin.

## Group Theory

- A proper error test has been installed for `ElementaryAbelianSeries` applied to matrix groups.
- Algorithms have been installed for computing the soluble radical and radical quotient of matrix groups over rings of integers modulo $n$ (type `RngIntRes`). This allows `SolubleRadical`, `RadicalQuotient`, `ElementaryAbelianSeries`, `IsIsomorphic`, `AutomorphismGroup` and `Subgroups` to be applied to this class of matrix group.
- A memory explosion when computing image and kernel of a homomorphism with domain a matrix group has been fixed. Bug reported by Derek Holt.
- A bug in the storing of characters with a group has been rectified. Bug reported by Markus Grassl.
- Routines for computing minimal coset and double coset representatives of standard parabolic subgroups in a `GrpFPCox` have been revised to include a length limit. These routines can now be applied to infinite Coxeter groups. Algorithms supplied by Bob Howlett.
- A crash in [`ToddCoxeter`](../FinitelyPresentedGroups/FPGroups/subgroup-general.md#function-grpfp-1-toddcoxeter), when the coset table could not be constructed, has been removed; the function now correctly returns 0 in such a case. Bug reported by Mike Newman.

## Invariant Theory

- A bug in computing invariants of the trivial matrix group, which occurred on Sun Sparcs, has been fixed. Reported by F. Quiring.
- The algorithms for computing primary and secondary invariants have been improved significantly.

## Lie Theory

- A bug in `StandardAction` for certain Coxeter groups has been fixed. Reported by M. Grassl.

## Local Rings

- Some fixes have been made to `Factorization` for polynomials over local rings and series rings.
- [`GaloisImage`](../LocalFields/PAdicRingsAndTheirExtensions/operation-element.md#function-galoisimage-rngpadelt-rngintelt) for default `UnramifiedExtension`s has been rewritten and is now much faster for large degree extensions.
- The constructor for `UnramifiedExtension` with `Cyclotomic=true` has been heavily speeded-up for small prime characteristics following updates to the Teichmuller lift code which gives the cyclotomic generator.

## Mappings

- A bug where the type of a composite map was set incorrectly has been fixed. Bug reported by Mike Newman.

## Module Theory

- A bug in the [`Meataxe`](../RepresentationTheory/ModulesOverAnAlgebraAndGroupRepresentations/structure.md#function-modalg-meataxe), in the hard case where the endomorphism ring was needed, has been fixed. Reported by E. O’Brien.

## Number Fields

- A bug in the code used for subset relations of orders has been fixed. Occasionally this would trigger internal errors even in standard computations of maximal orders.

## Polynomial Rings

- Bugs in [`SquarefreePart`](../BasicRings/MultivariatePolynomialRings/factorization-irreducibility.md#function-squarefreepart-rngmpolelt) in positive characteristic have been fixed. Reported by M. Grassl.
- A bug in polynomial quotient rings over integer residue rings has been fixed. Reported by H. Hubrechts.

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## Subgroups of $\mathrm{PSL}_2(\mathbb{Z})$

- A large class of congruences subgroups, defined with a character `chi` via [`CongruenceSubgroup`](../ModularArithmeticGeometry/CongruenceSubgroupsOfPSL2R/Congruence-subgroups.md#function-congruencesubgroup-rngintelt)`([N,N,1],chi)`, had been wrongly recognised as being equal to [`Gamma1`](../ModularArithmeticGeometry/CongruenceSubgroupsOfPSL2R/Congruence-subgroups.md#function-gamma1-rngintelt)`(N)`. This has been corrected and several other adjustments made so that the available functionality (including `Index`, `FareySequence` and `Genus`) is fully correct for all subgroups constructed using [`CongruenceSubgroup`](../ModularArithmeticGeometry/CongruenceSubgroupsOfPSL2R/Congruence-subgroups.md#function-congruencesubgroup-rngintelt).