Pytorch: Assign values from one mask to another, masked by itself

There are a few solutions, I will also give their speed as measured by timeit, 10k repetitions, on 2021 macbook pro.

The simplest solution, taking 0.260s:

active[active.clone()] = ~terminated

We can use masked_scatter_ inplace operation for abt. 2x speedup (0.136s):

active.masked_scatter_(
        active,
        ~terminated,
    )

Out of place operation, taking 0.161s, would be:

active = torch.masked_scatter(
        active,
        active,
        ~terminated,
    )