Singular

LIB "ncfactor.lib";
ring R = 0,(x1,x2,s1,s2),dp;
matrix C[4][4] = 1,1,1,1,
1,1,1,1,
1,1,1,1,
1,1,1,1;
matrix D[4][4] = 0,0,s1,0,
0,0,0,s2,
-s1,0,0,0,
0,-s2,0,0;
def r = nc_algebra(C,D);
setring(r);
poly h = x1*(x1+1)*s1^2-2*x1*(x1+100)*s1+(x1+99)*(x1+100);
facShift(h);
==> [1]:
==>    [1]:
==> 1
==>    [2]:
==>       x1*s1-x1+s1-100
==>    [3]:
==>       x1*s1-x1-s1-99
==> [2]:
==>    [1]:
==> 1
==>    [2]:
==>       x1*s1-x1-100
==>    [3]:
==>       x1*s1-x1-99
==> [3]:
==>    [1]:
==> 1
==>    [2]:
==>       x1*s1-x1-99
==>    [3]:
==>       x1*s1-x1-100