slimgb() takes more than four times longer in Singular 4.0.1 than in 3.1.7 (non-commutative example)

[steenpass]

The following example was tested with both Singular 3.1.7 (7caeacb) and 4.0.1 (13f5550) on wawa. Both jobs were started at the same time. While Singular 3.1.7 finished in little more than 6 hours, 4.0.1 is still running, for more than 25 hours now. This example was found by Shrawan.

ring r1 = 0, (x,y,Dx,Dy,s), (dp(4), dp(1));
matrix C[5][5] = 0,1,1,1,1,
                 0,0,1,1,1,
                 0,0,0,1,1,
                 0,0,0,0,1,
                 0,0,0,0,0;
matrix D[5][5];
D[1, 3] = 1;
D[2, 4] = 1;
def r2 = nc_algebra(C, D);
setring(r2);
basering;

ideal I = 5*x*y^4*Dx+6*y^5*Dx-y^5*Dy-5*x^4*Dy,
5*x^2*Dx+6*x*y*Dx+4*x*y*Dy+5*y^2*Dy-25*x*s-30*y*s,
125*x*y^3*Dx+25*y^4*Dx+100*y^4*Dy+1296*x*y^2*Dx-25*x^3*Dy+30*x^2*y*Dy-36*x*y^2*Dy+1080*y^3*Dy-625*y^3*s-6480*y^2*s,
625*x^2*y^2*Dx^2-275*y^4*Dx^2+1000*x*y^3*Dx*Dy+250*y^4*Dx*Dy+400*y^4*Dy^2+6480*x^2*y*Dx^2+1296*x*y^2*Dx^2+275*x^3*Dx*Dy-330*x^2*y*Dx*Dy+9900*x*y^2*Dx*Dy+1080*y^3*Dx*Dy-200*x^3*Dy^2+235*x^2*y*Dy^2-276*x*y^2*Dy^2+3780*y^3*Dy^2+4750*x*y^2*Dx+800*y^3*Dx+3700*y^3*Dy+42768*x*y*Dx-6480*y^2*Dx*s+1296*y^2*Dx+1085*x^2*Dy-1278*x*y*Dy+4320*y^2*Dy*s+33984*y^2*Dy-15625*y^2*s^2-20625*y^2*s-162000*y*s^2-181440*y*s,
3125*x^3*y*Dx^3+2275*y^4*Dx^3+7500*x^2*y^2*Dx^2*Dy+375*x*y^3*Dx^2*Dy-3675*y^4*Dx^2*Dy+6000*x*y^3*Dx*Dy^2+1800*y^4*Dx*Dy^2+1600*y^4*Dy^3+32400*x^3*Dx^3+6480*x^2*y*Dx^3-6480*x*y^2*Dx^3-2275*x^3*Dx^2*Dy+76170*x^2*y*Dx^2*Dy+20484*x*y^2*Dx^2*Dy-5400*y^3*Dx^2*Dy+3225*x^3*Dx*Dy^2-3785*x^2*y*Dx*Dy^2+56496*x*y^2*Dx*Dy^2+12420*y^3*Dx*Dy^2-1200*x^3*Dy^3+1380*x^2*y*Dy^3-1585*x*y^2*Dy^3+13050*y^3*Dy^3+31875*x^2*y*Dx^2-10125*x*y^2*Dx^2-12900*y^3*Dx^2+57000*x*y^2*Dx*Dy+4200*y^3*Dx*Dy+25200*y^3*Dy^2+298080*x^2*Dx^2-14256*x*y*Dx^2+32400*y^2*Dx^2*s-12960*y^2*Dx^2-17860*x^2*Dx*Dy+498282*x*y*Dx*Dy-47520*y^2*Dx*Dy*s+5004*y^2*Dx*Dy+12735*x^2*Dy^2-14686*x*y*Dy^2+16200*y^2*Dy^2*s+203466*y^2*Dy^2+94500*x*y*Dx+50625*y^2*Dx*s+4275*y^2*Dx-37500*y^2*Dy*s+77100*y^2*Dy+698076*x*Dx-162000*y*Dx*s^2+168480*y*Dx*s-27216*y*Dx-26066*x*Dy+108000*y*Dy*s^2-136080*y*Dy*s+565566*y*Dy-390625*y*s^3-562500*y*s^2-344375*y*s-4050000*s^3-5022000*s^2-2323980*s,
x*y^5+y^6+x^5;

int t = timer;
ideal J = slimgb(I);
t-timer;

[Oleksandr]

what about std ?