Opened 12 years ago

Closed 12 years ago

# Singular crashes when I try to calculate the radical of an ideal.

Reported by: Owned by: klooster@… seelisch major 3-1-4 and higher singular-libs 3-1-0 primdec.radical

(See attachment)

Input/output

### Changed 12 years ago by Oleksandr

output of Singularg (recent trunk version)

### comment:1 Changed 12 years ago by seelisch

Owner: changed from somebody to seelisch

### comment:2 Changed 12 years ago by gorzel

1. The essence of the crash is the following bug:
```>  ring Ra = (0,a),x,dp;
>  poly f0 = a*(a2+a+1);
>  poly f1 = a*(a2+a+1) +1;
>  ring ra = (0,a),x,dp;
>  minpoly = a2+a+1;
>  imap(Ra,f1);
1
>  imap(Ra,f0);
Singular : signal 11 (v: 3130/ 14215 ):
current line:>> imap(Ra,f0);<<
Segment fault/Bus error occurred at 2b7d5ebff260 because of 10246 (r:1305549581)
trying to restart...

```

2.) Altough, I guess, it is not too difficult to fix this bug, it seems that the

proc radical is limited for computations for rings (in char 0 ?) without algebraic extension. (The minpoly is not just "forgotten" but it can not be set in the implementation since some variables are moved to parameters.) Or, will the result always be correct when the coefficients of intemediate results are finally reduced by the minpoly?

3.) @klooster: Despite this unsolved question yet, Singular can easily compute the radical:

(I have simplified the code a little bit.)

```> LIB "linalg.lib";
> ring R=(0,a),(x,y,z),dp;
> minpoly = a2+a+1;
> poly f1=x3+y3+z3;
> matrix m[3][3]=1,0,1,1,0,a,1,1,0;
> matrix v[3][1]=x2,y2,z2;
> map phir=R,(-det(m)*inverse(m)*v);
> poly f2=phir(f1);
> option(redSB);
> facstd(jacob(f2));
[1]:
_[1]=z
_[2]=x-y
[2]:
_[1]=z
_[2]=x+y
[3]:
_[1]=y
_[2]=x2+(-a-2)*z2
[4]:
_[1]=x
_[2]=y2+(a-1)*z2

```

### comment:3 Changed 12 years ago by seelisch

Resolution: → fixed new → closed

fixed with revision 14234 (fix in longalg.cc)

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