Change log for Magma V2.19-6 (Released 17/5/2013)

Algebraic Curves

·Crashes when pulling back points under maps between hyperelliptic curves, which were caused by some recent changes, have been fixed.

Arithmetic Geometry

·Significant improvements to performance of the routine for solving conics over number fields, HasRationalPoint, have been made.

·A runtime error in IsLocallySolvable has been fixed, in the part of the function that blows up singular points (not triggered by most input). Reported by Jeremy Rouse.

Function Fields

·The FunctionField of a sequence of multivariate polynomials now has more natural field generators (F.1 etc). This is a deprecated function that will be removed in later versions. We recommend that users use the curve version to create function fields where there are structures in place to properly convert between rational functions and elements of the function field(s).

Groebner Bases

·A bug in radical in small characteristic (arising when computing reduced subschemes) has been fixed. Reported by Damiano Testa.

Groups

·A crash in MolienSeries of a matrix group over the complex field has been fixed by banning the use of MolienSeries for groups over inexact fields. Bug encountered by an unknown calculator user.

·The generators of ChevalleyGroup E7 have been changed to a Steinberg pair where the first generator is diagonal. The second generator has not been changed. The corrected generator was supplied by Don Taylor, at the request Eamonn O'Brien.

·A crash in automorphism groups has been fixed.

·The default size of a coset table for the Todd-Coxeter procedure has been increased by a factor of 10. This affects order, index, and coset table calculations for finitely presented groups. This limit, and many others, may be reset by the user using the SetGlobalTCParameters intrinsic procedure. The relevant parameter for this change is Workspace.

·Some extraneous printing in the sporadic group package has been removed. Fixed by Eamonn O'Brien.

·The implementation of the CharacterDegrees intrinsic for p-groups has been improved. The algorithm remains that of M.C. Slattery (1986).

Hilbert Modular Forms.

·Excessive memory usage in the "indefinite" algorithm (Greenberg-Voight) has been improved. Reported by Armand Brumer.

Integer Ring

·A bug has been fixed in BitwiseAnd that could cause a crash when applied to large integers with the result being smaller (such as zero).

Monoids

·A bug in Content applied to elements of an ordered monoid which changed the word has been fixed. Bug reported by Andreas Previtali.

Number Fields

·Some fixes have been made to the ClassGroup routine, improving bad performance in some special situations.

·NormEquation, in the case of orders of number fields of degree 2 (i.e. type RngOrd), only worked for small input. In other cases it could incorrectly return false or fail to terminate. It has been fixed by calling a different algorithm as appropriate. Reported by Nils Bruin.

·A bug in PowerProduct has been fixed: runtime/internal errors sometimes occurred when the given base elements were not integral.

·An iterator for quotients of orders by ideals has been provided.

·Random has been provided for quotients of orders by ideals.

·The euclidean operations for elements of quotients of orders by ideals have been fixed and expanded, including the provision of div, mod, Quotrem, Lcm, Gcd, XGcd and EuclideanNorm.

·Annihilator has been provided for elements of quotients of orders by ideals.

·A repeated calculation has been removed from the computation of Subfields of number fields in absolute representation.

Pseudo-Random Bit Sequences

·A bug in LFSRSequence has been fixed; this bug could cause a crash when the polynomial was defined over a ring that was not a finite field.

System

·A crash in ListTypes has been fixed.

·Improvements have been made to the memory manager so that jobs allocating a large number of large blocks are less likely to run out of MMAP regions. Problem reported by E. O'Brien.

·The memory manager has also been sped up in the case that very many blocks of similar size are deleted at the same time.