Simplify taking a long time

[David Menéndez Hurtado]

Hi,

I have a very complicated expression. Running simplify on it takes a long time (running for 70 h and counting), while other similar or even longer expressions have been done in a few minutes. Is it possible that it has entered an endless loop?

The expression as is is good enough for my purposes, but I wanted to report a possible bug.

a0, a1, a2, b0, b1, b2, c0, c1, c2 = symbols(vector_components, real=True)
angle, torsion = symbols(input_angles, real=True)
length, prev_length = symbols(input_lengths, real=True, positive=True)

c0 + length*((a1 - b1)*(b2 - c2) - (a2 - b2)*(b1 - c1))*sin(angle)*sin(torsion)/sqrt(((a0 - b0)*(b1 - c1) - (a1 - b1)*(b0 - c0))**2 + ((a0 - b0)*(b2 - c2) - (a2 - b2)*(b0 - c0))**2 + ((a1 - b1)*(b2 - c2) - (a2 - b2)*(b1 - c1))**2) + length*(-b0 + c0)*cos(angle)/prev_length + length*((b1 - c1)*((a0 - b0)*(b1 - c1) - (a1 - b1)*(b0 - c0)) + (b2 - c2)*((a0 - b0)*(b2 - c2) - (a2 - b2)*(b0 - c0)))*sin(angle)*cos(torsion)/(prev_length*sqrt(((a0 - b0)*(b1 - c1) - (a1 - b1)*(b0 - c0))**2 + ((a0 - b0)*(b2 - c2) - (a2 - b2)*(b0 - c0))**2 + ((a1 - b1)*(b2 - c2) - (a2 - b2)*(b1 - c1))**2))



Thanks,

/David.

[Aaron Meurer]

It should be considered a bug in simplify. It's probably not stuck in
an endless loop, but rather just an extremely inefficient algorithm.
If you end up canceling it with Control-C open an issue with the
traceback so we can see where it got stuck.

Aaron Meurer

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[David Menéndez Hurtado]

On Tuesday, September 15, 2015 at 7:46:27 AM UTC+2, Aaron Meurer wrote:

It should be considered a bug in simplify. It's probably not stuck in
an endless loop, but rather just an extremely inefficient algorithm.
If you end up canceling it with Control-C open an issue with the
traceback so we can see where it got stuck.

Aaron Meurer

Sorry for the late reply. I can confirm it was not stuck, and took more than four days but less than a week to finish. The final expression was almost the same, with only a minor change:

+ ((a1 - b1)...)

- ((- a1 + b1)...)

Since I have to rerun it again anyway, I can do so under cProfile. Would that be more helpful than the traceback?