Mark Dickinson <[email protected]> added the comment:
That computation of the shift can be simplified to require only one popcount
operation. With F and Finv as before:
def comb_small(n, k):
assert 0 <= k <= n <= Nmax
return (F[n] * Finv[k] * Finv[n-k] % 2**64) << (k ^ n ^ (n-k)).bit_count()
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Python tracker <[email protected]>
<https://bugs.python.org/issue37295>
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