contract_path with optimize='optimal' not working on small example

[ryan112358]

Cross posting from jax-ml/jax#24929

import opt_einsum
import numpy as np

formula = 'a,c,d,db,ab,cb,ac,cd,ad,b->dbc'

arrays = [np.random.rand(*(2,)*len(key)) for key in formula.split('->')[0].split(',')]
opt_einsum.contract_path(
    formula, *arrays, einsum_call=True, use_blas=True, optimize='optimal')  # this hangs and does not complete

[dgasmith]

One caution is the optimal algorithm scales factorially, with 10 input arrays you are generally pushing the limits with 10's of seconds to minutes runtime. You will find similar results with the dp algorithm which has much better runtimes or this particular contraction can be evaluated with greedy for what is likely to be the optimal path. We generally recommend optimize='auto' to balance path finding/path quality for input formula. More information can be found here.

I'll check out your example to see if it's an actual hang or just a long path evaluation time.