Change log for Magma V2.18-12 (Released 13/11/2012)

Algebraic Curves

·Some problems with residue fields of curves have been fixed.

·An incorrect assertion that was causing occasional crashs in IsHyperelliptic and CurveQuotient has been fixed.

Algebraic Fields

·Residue fields of some places have been optimized.

·The inertia degree computation of some prime ideals of relative extensions has been corrected.

Algebraic Number Fields

·A memory issue in ext<> has been fixed.

·An error message from meet of an order with a number field has been corrected.

Elliptic curves

·TwoDescent of elliptic curves over Q has been improved, fixing extremely bad performance for curves of large conductor with a single two-torsion point. Reported by R. Rathbun.

·In EightDescent, some bugs have been fixed which triggered runtime errors in occasional cases. Reported by R. Rathbun.

·A bug has been fixed in EllipticCurveSearch which caused it to sometimes be very slow for fields of degree 4 or more. Reported by L. Dembele.

Groups

·The construction of BSGS for a matrix group will check if the group is known to be infinite, and will trigger a runtime error if it is. Reported by M. Grassl.

·A crash in ClassicalMaximals when the normalise parameter is set to true has been fixed. Reported by E. O'Brien, fixed by D. Holt.

Lattices

·A crash computing isometry of two lattices with empty sequences of extra forms has been fixed. Reported by M. Kirschmer.

Modular forms

·A much faster version of OverconvergentHeckeSeries has been included. Due to A. Lauder.

Polynomial Rings

·A crash in ColonIdeal for ideals over residue class rings has been fixed. Reported by J. Shotton.

·XGCD now returns all 3 return values when called directly in print mode. Reported by D. Passman.

·Evaluation of polynomials at matrices over finite fields has been sped up.