bpo-44376 - reduce pow() overhead for small exponents #26662
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Reduce pow() overhead for small exponents. Incidentally fixed a refcount oversight for negative exponents.
tim-one
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It's annoying, but I don't want to fight about it ;-)
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Wow - that appeared to do the trick! Thank you 😄. |
mdickinson
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Jun 11, 2021
instead of left-to-right. This cuts the time for exponent 2 by another 10%. Does that slow things for, e.g., an exponent like 1 << 20? Sure, by a little. But that exponent will go on to do 20 squarings, and the extra native 32-bit shift- and-tests in the loop are insignificant in comparison. For a tiny exponent (like 2), the loop's shift-and-tests can consume a significant part of the total time. Also reverted the change I made to repair refcounting in modular inverse code. Mark will make the change in a distinct PR, and backport it. Without this change, the "negative refcount" glitch stopped showing up in this PR's code after I changed it to never return `a` directly.
until the exponent is at least 4. Saves approaching another 10% for exponent 2.
insteads works OK, but was always a conceptual mess.
Close to another 10% saved for exponent 2.
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Jun 19, 2021
Greatly reduce pow() overhead for small exponents.
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BPO-44376
Reduce pow() overhead for small exponents.
Incidentally fixed a refcount oversight for
negative exponents.
https://bugs.python.org/issue44376