Avoid variables in power

[python-ista]

Hi there!

I'm getting used to the syntax and features of PySR and think it's excellent! One issue I'm having is with setting constraints on the power law. I wouldn't mind having a result (e.g. x_0^{0.3125} but I want to try avoiding powers to another variable, (e.g. x_0^{0.3125 x_1}).
I saw the constrain (-1,1) for pow, but this seems to allow variables and constants. Is there a way to set it to only allow constants?

Also, could someone shed light on what the numbers actually represent?

Thanks!

[MilesCranmer]

Hi @python-ista!

(-1, 1) means that the left argument (in pow, this is the base) can have arbitrarily large complexity, while the 1 signifies that the right argument can only have complexity of at most 1. By default, all operators, variables, and constants have a complexity of 1. The total complexity of an expression is computed but summing the individual complexities.

One thing you could try is to set complexity_of_variables=2 which, along with constraints={"pow": (-1, 1)}, would prevent variables appearing in the exponent while still allowing constants.

Cheers,
Miles

[python-ista]

Hi Miles!
wow, such an obvious and simple way to do it! thanks!