Title: Change log for Magma V2.21-2
Author: Computational Algebra Group

Change log for Magma V2.21-2 (Released 12/2/2015)

Coding Theory

•ConstaCyclicCode is more efficient now, particularly for long codes where the constant has large order. Reported (and fixed) by M. Grassl.

Commutative Algebra

•A crash in PrimaryDecomposition over function fields has been fixed. Reported by M. Stoll.

Groups

•The new Group intrinsic did not operate correctly when given strings with "SU" involved. Similarly, "U" has been included as a synonym for "PSU".

Multivariate Polynomials

•The deprecated parameter Digits has been removed from the Variety and VarietySequence intrinsics.

Number Fields

•A problem with HeckeCharacterGroup of an abelian extension was fixed, taking into account infinite places.

•The Extend intrinsics for Dirichlet and Hecke characters (and groups) have been modified to eliminate the extraneous second return value (there is not really a kernel involved). The Extend intrinsic for groups thus now returns a group of the same size.

•The application of an automorphism to a fractional ideal of an order of a quadratic field has been fixed. Reported by M. Kirschmer.

•The error checking in LLL and LLLBasisMatrix when the input is an ideal of an order of a number field has been improved to give a runtime error when the number field is not a direct extension of the rational field.

•A problem with MinimalPolynomial was fixed, when the polynomial that was found had degree 0 (and thus trivial factorisation).

Schemes

•Projective points with coordinates in Euclidean domains are now more strictly checked and as a result some points which have previously been able to be constructed are no longer able to be constructed.

System

•Using sequence indexing on large strings (greater than 2GB) now works properly.

•Read has been slightly sped up for larger files.

•Some unnecessary memory duplication when calling eval has been removed.

Topology

•Printing of objects of type SmpCpx has been fixed. Reported by K. Joanidis.

Vector Spaces

•An incorrect answer has been fixed for the function ExtendBasis. Reported by R. Zeier.