Add `machine_pow` to ARNN
Created by: wdphy16
I think the interface is still a bit strange. AbstractARNN.machine_pow
cannot be an optional field, because the child classes will add non-optional fields after it.
ARDirectSampler.machine_pow
has no effect as before, but I used it to pass machine_pow
to AbstractARNN
in the test. Maybe I should add a warning if the user trys to set it.
After we agree on the interface, I'll add the changelog.
As the number of tests for ARNN is growing exponentially, I added an option --arnn_test_rate
to randomly (and deterministically) run only a portion of them.