Opened 9 years ago

Closed 9 years ago

# new example for incomplete primdecSY() decomposition

Reported by: Owned by: kroeker@… somebody minor 4-1-0 and higher dontKnow 4-0-1 incomplete decomposition primdecSY() minpoly

### Description

```LIB("primdec.lib");
LIB("ehv.lib");
ring rng = (5,vv),(xx,yy,zz,ww),dp;
minpoly = (vv^2-2);
ideal I = (2*vv)*xx*yy+(vv)*xx*ww+zz,(-vv)*xx^2*zz+2*zz;
list L1, L2;
int i ;

// despite using fixed random seed, primdecSY() sometime succeeds. (why?)
for (i=0; i<20; i++)
{
system("random",1803001481);
L1 = primdecGTZ (I);
L2 = primdecSY (I);
"i";i;
"L1";L1;
"L2";L2;
ASSUME(0, primDecsAreEquivalent (L1,L2) ) ; // will fail!
}
```

output:

```L1
[1]
[1]
_[1]=zz
_[2]=yy-2*ww
[2]
_[1]=zz
_[2]=yy-2*ww
[2]
[1]
_[1]=zz
_[2]=xx
[2]
_[1]=zz
_[2]=xx
[3]
[1]
_[1]=xx*zz-yy+2*ww
_[2]=yy^2+(-vv)*zz^2+yy*ww-ww^2
_[3]=xx*yy-2*xx*ww+(-vv)*zz
_[4]=xx^2+(-vv)
[2]
_[1]=xx*zz-yy+2*ww
_[2]=yy^2+(-vv)*zz^2+yy*ww-ww^2
_[3]=xx*yy-2*xx*ww+(-vv)*zz
_[4]=xx^2+(-vv)
L2
[1]
[1]
_[1]=xx*yy-2*xx*ww+(-vv)*zz
_[2]=xx*zz^2-yy*zz+2*zz*ww
_[3]=yy^2*zz+(-vv)*zz^3+yy*zz*ww-zz*ww^2
_[4]=xx^2*zz+(-vv)*zz
_[5]=xx^3+(-vv)*xx
[2]:
_[1]=zz
_[2]=xx
[2]
[1]
_[1]=zz
_[2]=yy-2*ww
[2]
_[1]=zz
_[2]=yy-2*ww

```

### comment:1 Changed 9 years ago by hannes

Resolution: → fixed new → closed
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