Hi,
The patches attached to ticket #12068 (Numerator for symbolic expression
shouldn't use maxima) were applied to sage-5.0.beta, which I was happy to
see because I had tried to do something similar (#10268, which can probably
be closed) to use GiNaC's normal() function for rational expressions
instead of the corresponding Maxima function. However, my version was
stalled by a GCD bug (#10284) that was fixed in GiNaC but not in sage.
Basically, when normal() is called it puts expressions under a common
denominator and then tries to cancel the greatest common factor, which can
cause sage to hang. Alas, the same issue arises when the patches on #12068
are applied:
sage: a = var('a')
sage: b = var('b')
sage: c = var('c')
sage: x = 4*(b^2 + 1)^2*(2*a^4*b*c^2 + a^3*b^2*c^2 - 2*a^4*b + a^3*b^2 -
a^3*c^2 - a*b^2*c^2 - a^3 - a*b^2 + a*c^2 + 2*b*c^2 + a - 2*b)^2/((c^2 +
1)^2*((3*a^4 + 2*a^2 + 3)*b^4 + 3*a^4 + 2*(a^4 - 2*a^2 + 1)*b^2 + 2*a^2 +
3)^2) + 4*(a^2 + 1)^2*(a^2*b^3*c^2 + 2*a*b^4*c^2 - a^2*b^3 - a^2*b*c^2 +
2*a*b^4 - b^3*c^2 + a^2*b + 2*a*c^2 + b^3 + b*c^2 + 2*a - b)^2/((c^2 +
1)^2*((3*a^4 + 2*a^2 + 3)*b^4 + 3*a^4 + 2*(a^4 - 2*a^2 + 1)*b^2 + 2*a^2 +
3)^2) + 4*(a^4*b^3*c^2 - a^3*b^4*c^2 - a^4*b^3 - a^4*b*c^2 - a^3*b^4 -
2*a^3*b^2*c^2 + 2*a^2*b^3*c^2 + a*b^4*c^2 + a^4*b - 2*a^3*b^2 - a^3*c^2 -
2*a^2*b^3 - 2*a^2*b*c^2 + a*b^4 + 2*a*b^2*c^2 + b^3*c^2 - a^3 + 2*a^2*b +
2*a*b^2 + a*c^2 - b^3 - b*c^2 + a + b)^2/((c^2 + 1)^2*((3*a^4 + 2*a^2 +
3)*b^4 + 3*a^4 + 2*(a^4 - 2*a^2 + 1)*b^2 + 2*a^2 + 3)^2)
sage: x.simplify_rational() # less than 1 second
8*(a^2*b^4 + (a^2*b^4 + (a^3 - a)*b^3 + (a^4 + 1)*b^2 - (a^3 - a)*b +
a^2)*c^4 - (a^3 - a)*b^3 + (a^4 + 1)*b^2 + 2*(a^2*b^4 - (a^4 + 1)*b^2 +
a^2)*c^2 + (a^3 - a)*b + a^2)/((3*a^4 + 2*a^2 + 3)*b^4 + ((3*a^4 + 2*a^2 +
3)*b^4 + 3*a^4 + 2*(a^4 - 2*a^2 + 1)*b^2 + 2*a^2 + 3)*c^4 + 3*a^4 + 2*(a^4
- 2*a^2 + 1)*b^2 + 2*((3*a^4 + 2*a^2 + 3)*b^4 + 3*a^4 + 2*(a^4 - 2*a^2 +
1)*b^2 + 2*a^2 + 3)*c^2 + 2*a^2 + 3)
sage:
sage: x.normalize() # hang in infinite loop
So, does anyone have any ideas about how to proceed. Using GiNaC's normal()
is very useful, but it is hard to know in advance when it will hang and
when it does you have to kill your sage session.
Thanks,
Ben
--
To post to this group, send an email to sage-devel@googlegroups.com
To unsubscribe from this group, send an email to
sage-devel+unsubscr...@googlegroups.com
For more options, visit this group at http://groups.google.com/group/sage-devel
URL: http://www.sagemath.org
