[issue37295] Possible optimizations for math.comb()

[Stefan Pochmann]

Stefan Pochmann <stefan.pochmann at gmail.com> added the comment:

Turns out for n=100_000, k=50_000, about 87% of my factors are 1, so they don't even need to be turned into Python ints for multiplication, improving the multiplication part to 3.05 ms. And a C++ version to produce the factors took 0.85 ms. Updated estimation:

1510.4 ms  math.comb(n, k)
 460.8 ms  factorial(n) // (factorial(k) * factorial(n-k))
   3.9 ms  *estimation* for mycomb if written in C

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<https://bugs.python.org/issue37295>
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