Change log for Magma V2.23-4 (Released 15/9/2017)

Algebras

·A missing error check for JacobsonRadical for algebras over non-supported rings has been added.

Commutative Algebra

·A crash in SyzygyModule for certain types of polynomial rings defined over the rational field has been fixed. Reported by M. Reid.

·A subtle bug in PrimaryDecomposition (occurring very rarely for ideals in characteristic zero) has been fixed.

Elliptic Curves

·A (very rare) infinite recursion in the point counting algorithm when used with ellpitic curves defined over non-default finite fields has been fixed. This led to problems with the Order function too which have been fixed. Reported by C. Cheng.

Galois Groups

·Extra printing has been removed from the computation of Galois groups of reducible polynomials. Reported by D. Krumm.

Groebner Bases

·A non-trivial slow down in the dense F4 algorithm over GF(2) has been fixed. Further improvements have been added at the same time.

Groups

·A crash in unipotent matrix groups has been fixed. Bug reported by E. O'Brien.

·A new version of the function ClassTwo to count p-class 2 p-groups is distributed which incorporates improvements by Michael Vaughan-Lee and is much faster than the original.

Integer Residue Class Rings

·A crash in the preimage application of the multiplicative map for large residue rings has been fixed. This preimage computation has also been considerably sped up.

Invariant Theory

·A crash in FundamentalInvariants for invariant rings over inexact rings has been fixed.

Local Rings

·A fix has been made to the Factorization of polynomials over local rings. Reported by E. ThomÃ©.

Matrices

·A crash in Solution for matrices defined over multivariate polynomial rings has been fixed.

·The base algorithm for matrix multiplication in moderately small dimension has been improved for matrices over GF(4), GF(5) and GF(7).

·The base algorithm for matrix echelonisation in moderately small dimension has been improved for matrices over GF(4).

Modular Arithmetic Geometry

·A crash in DualHeckeOperator has been fixed. Reported by D-A. Guiraud.

Polynomial Rings

·A leak in bivariate multiplication over rings with elements stored in blocks has been fixed. Reported by D. Barth.

·A bug in IsPrime and IsIrreducible for polynomials over the integers has been fixed. Reported by J. Klueners.

·A crash in multiplication of polynomials defined over matrices has been fixed.

Real and Complex Fields

·A hang and some accuracy errors in complex root finding have been fixed. Reported by J. Klueners.

Series Rings

·A fix has been made to the Roots computation for polynomials over series rings whose degree is the characteristic of the coefficient ring. Reported by J. Tuitman.