Change log for Magma V2.10-7 (Released 7/5/2003)

Coding Theory

·A minor bug that occurs when using BCH decoding with a linear code has been fixed.

Documentation

·Some very minor typographical errors in the Handbook and HTML help have been fixed.

Geometry

·Two minor fixes were made to the elliptic curve function pPowerTorsion in response to a problem reported by J Cremona.

·The covering structure of parents of places on curves is only defined if it is trivial, i.e. if the places have the identical PlcCrv's and hence belong to the same curve.

Groups

·FPGroupStrong has been altered so that it does not change the base of the group. This fixes a bug found in a CohomologyModule calculation with a 2-subgroup of Alt(8).

·Added EliminateRedundantBasePoints(GrpPerm). Related to the above.

·The function CohomologyModule was fixed by Derek Holt to work in the case of the trivial group. The bug was arose in a CohomologyModule calculation with the trivial 2-subgroup of Alt(8).

·Crash caused by ChangeBase( GrpPerm, []) fixed. Bug was found in CohomologyModule calculation with 2-subgroup of Alt(8).

·A bug has been fixed in a filtered version of the function Subgroups(G) which resulted in subgroups being missed. The problem occurred in the case in which maximal subgroups for G are computed using Derek Holt's code. The bug was demonstrated with Subgroups(PGammaL(2, 11^2) : IndexLimit := 5).

·The random Schreier algorithm for matrix groups has been modified to produce (probable) shallow Schreier trees. This overcomes some crashes due to memory problems caused by long words, and should substantially improve the efficiency of working in a matrix group with a BSGS.

Linear Algebra

·An error reported by E Thome in creating a sparse matrix over a an integer residue class ring has been fixed.

Rings and Fields

·An improved algorithm for computing the power of a univariate polynomial with coefficients in a finite field has been implemented. Suggested by M Grassl.

·Serious memory leaks in the calculation of class groups have been fixed.

·A problem that occurred when checking the defining polynomials in the ext constructor for function fields has been fixed.

Sets and Sequences

·The sequence function Position has been changed so that if the sequence has been sorted with respect to the natural ordering of its elements, the position of an element is found using a binary search rather than a sequential search.