BUG: don't use pow for integer power ufunc loops. #7496
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| if (in2 & 1) { | ||
| out *= in1; | ||
| } | ||
| in2 >>= 1; /* Shift exponent down by 1 bit */ |
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Please put the comment on the line before the code.
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Could you put a test in maybe from the cited issue? |
| out *= in1; | ||
| } | ||
| in2 >>= 1; /* Shift exponent down by 1 bit */ | ||
| if (in2 == 0) { |
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Does this really speed things up at all? You are doing one check per iteration in order to save yourself a single multiplication in the last one, does it pay off.
If there is any performance to be gained there, you could alternatively peel off the first multiplication as an assignment, so that a single check is needed:
out = in2 & 1 ? in1 : 1;
in2 >>= 1;
while (in2 > 0) {
in1 *= in1;
if (in2 & 1) {
out *= in1;
}
in2 >>= 1;
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I have no idea really. This code is lightly adapted from the integer power code used for scalars.
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Test added. I switched to using your version @jaimefrio. When I tested this, it either made no difference or a minuscule difference in run time with your version being the ever so slightly faster. |
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But in fairness, eliminating one multiplication is a bigger deal when finding squares or cubes relative to 62 powers. |
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Thanks Eric! |
Fixes gh-7405.