Opened 10 years ago

Last modified 9 years ago

## #638 new bug

# ffsolve.lib gives run time errors and wrong solutions

Reported by: | Owned by: | hannes | |
---|---|---|---|

Priority: | major | Milestone: | 4-1-0 and higher |

Component: | singular-libs | Version: | 4-0-0 |

Keywords: | ffsolve | Cc: |

### Description

Consider the Hermitian curve y^{2 = x}3 + x over GF(4).
It has eight points in GF(4)^{2. When one tries to find its
zeros by ffsolve.lib, it gives run time errors or wrong answers
I give three example codes:
}

LIB "ffsolve.lib"; ring r=(2,a),(y,x),lp; minpoly=a2+a+1; r; poly defeq = -y^2 + x^3 + x; // Hermitian curve over GF(4) with 8 points. ffsolve(ideal(defeq)); // returns only 4 points

// Second example LIB "ffsolve.lib"; ring r2=(2,a),(y,x),wp(3,2); minpoly=a2+a+1; r2; poly defeq = -y^2 + x^3 + x; // Hermitian curve over GF(4) simplesolver(ideal(defeq)); // returns the empty list ffsolve(ideal(defeq)); // run time error

// Third example LIB "ffsolve.lib"; ring r3=(4,a),(y,x),lp; // definition of a finite field without min-poly. r3; poly defeq = -y^2 + x^3 + x; // Hermitian curve over GF(4) with 8 points. ffsolve(ideal(defeq)); // run time error

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