Opened 8 years ago

Closed 8 years ago

# phantom component in a 'primdecGTZ()' decomposition

Reported by: Owned by: kroeker@… somebody minor 4-1-0 and higher dontKnow 4-0-1 phantom component primdecGTZ() bug

### Description

4th entry in decomposition L is not a component of the ideal I:

```LIB("primdec.lib");
option(redTail);
option(redSB);
ring rng = (0),(xm,xg,xr,xw,xj,xa,xi,xq),dp;
ideal I = -3*xg*xi+30*xm^2,
16*xw*xq-7*xr*xa,
-17*xg*xi*xq-7*xm*xr*xq,
-22*xm*xg+11*xw^2;

def L = primdecGTZ (std(I));

size(L);
L[4][1];
isSubModule(I, L[4][1] );

testPrimary( L , I ) ;

def L2 = primdecSY (std(I));
size(L2);
testPrimary( L2 , I ) ;
```

output:

```. size(L);
8

> L[4][1];
_[1]=xq
_[2]=xa
_[3]=7*xg*xr+85*xw^2
_[4]=5*xm*xw^2-xg^2*xi
_[5]=7*xm*xr+17*xg*xi

> isSubModule(I, L[4][1] );
0
>
. testPrimary( L , I ) ;
0
>
. def L2 = primdecSY (std(I));
> size(L2);
7
> testPrimary( L2 , I ) ;
1

```

### comment:1 Changed 8 years ago by hannes

Resolution: → fixed new → closed
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