option("redSB") in quotient rings produces unexepected results and Segment fault

[laplagne]

Over quotient rings, if the option("redSB") is set, the groebner bases are sometimes not reduced. They can even contain repeated polynomials.

This causes Segment Faults when using other procedures.

Here is the example.

SINGULAR /

A Computer Algebra System for Polynomial Computations / version 3-1-0

0<

by: G.-M. Greuel, G. Pfister, H. Schoenemann \ Aug 2008

FB Mathematik der Universitaet, D-67653 Kaiserslautern \ executing /users/urmel/alggeom/hannes/murrumesh/LIB/.singularrc

ring r = 0, (x, y), ds; ideal I = x2-y3; qring q = groebner(I); ideal U1 = x2, xy2; ideal U2 = xy2, y3; groebner(U2);

_[1]=xy2 _[2]=y3

option("redSB"); groebner(U2);

_[1]=y3 _[2]=xy2 _[3]=y3

std(U2);

_[1]=y3 _[2]=xy2 _[3]=y3

reduce(U1, groebner(U2));

Singular : signal 11 (v: 3100/2009021209): Segment fault/Bus error occurred at 2ac2a7af02d0 because of 10297 (r:1235731989) please inform the authors trying to restart...

(I used here a local ordering, but similar things happen under global orderings.)

[laplagne]

Singular script that produces the Segment Fault

[hannes]

both bugs fixed.