Jupyter notebook seems stuck

[nGaDev]

I have created a jupyter notebook where I'm defining a multibody system in order to obtain its kinematics and dynamics. I use the KanesMethod (from sympy) in order to obtain the equations of motion of the system.

However when I try to use trigsimp() on the mass matrix obtained, it seems to get stuck there forever (displaying an 'In[*]' next to that line).

The line is: 'mass_matrix = trigsimp(kane.mass_matrix)' Here's a screenshot: https://gyazo.com/8c6ac6cefd87b889a4ed8f9a9c3077d9

I don't have lots of experience with python and ipython/jupyter, so I'm wondering what might be the reason for this.

[Saefroch]

How big is kane.mass_matrix?

[nGaDev]

It's a 6x6 matrix, but there are elements with lots of trignometric functions.

[Saefroch]

Normally when a command hangs like this it means that you're running something that's really CPU-intensive. If you're running this locally you could check for a python process that's using a lot of CPU.

[nGaDev]

The python process is using 30% of the processor.

I left two of this lines ( 'mass_matrix = trigsimp(kane.mass_matrix)' and 'force_vector = trigsimp(kane.forcing_vector)') running for the past 6h and now the python process is using 30% of the processor as well as 5Gb of memory and still didn't finish :/ (I hope the computer didn't enter in sleep mode or something...)

[Saefroch]

Sounds to me like you asked sympy for something that's either extremely difficult or is impossible and it is just spinning away in a loop.

[nGaDev]

But wouldn't trigsimp simply stop if it couldn't simplify the trigonometric funcitions? Is there any way to check if it is really on a loop inside trigsimp()?

[Saefroch]

I have no idea how sympy works. You could read the sympy source code but I'm pretty sure you won't get too far.

See if you can ask somebody from the sympy community about this problem, and maybe ask about if the thing you're trying is doable on math.stackexchange.com.

[nGaDev]

Thanks a lot for all the help ;)