| msg260126 - (view) |
Author: Yury Selivanov (yselivanov) *  |
Date: 2016-02-11 19:33 |
| This patch implements a fast path for &, |, and ^ bit operations for single-digit positive longs. We already have fast paths for ~, and pretty much every other long op. -m timeit -s "x=21827623" "x&2;x&2;x&2;x&333;x&3;x&3;x&4444;x&4" with patch: 0.181 without patch: 0.403 -m timeit -s "x=21827623" "x |
21222;x |
23;x |
| msg260136 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2016-02-11 22:21 |
| fast_bits.patch LGTM. But it would be better to have at least two reviews. |
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| msg260190 - (view) |
Author: Марк Коренберг (socketpair) * |
Date: 2016-02-12 17:48 |
| You should add a tests. especially for edge cases, for negative values for example. |
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| msg260191 - (view) |
Author: Yury Selivanov (yselivanov) * |
Date: 2016-02-12 17:54 |
| > You should add a tests. especially for edge cases, for negative values for example. There are many binop tests in test_long.py |
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| msg260192 - (view) |
Author: Serhiy Storchaka (serhiy.storchaka) * |
Date: 2016-02-12 18:48 |
| Does this patch have effect with results over 8 bits? Does it have effect after applying patches from 24165? |
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| msg260196 - (view) |
Author: Yury Selivanov (yselivanov) * |
Date: 2016-02-12 19:40 |
| > Does this patch have effect with results over 8 bits? -m timeit -s "x=2**40" "x&2;x&2;x&2;x&333;x&3;x&3;x&4444;x&4" with patch: 0.404usec without patch: 0.41 > Does it have effect after applying patches from 24165? I'm not sure how it's related, but let's modify the test to stress the mem allocation: -m timeit -s "x=21827623" "(x+x)&2;(x+x)&2;(x+x)&2;(x+x)&333;(x+x)&3;x&3;(x+x)&4444;(x+x)&4" this patch+freelist: 0.337usec only freelist: 0.496 In any case, bit operations are often used for bit-flags logic, where numbers are usually aren't too big (it's rare to see more than 30 bit flags on one field). |
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| msg260197 - (view) |
Author: Yury Selivanov (yselivanov) * |
Date: 2016-02-12 19:42 |
| > with patch: 0.404usec without patch: 0.41 Sorry, I made a typo: these results should be flipped -- 0.41-0.404 is the overhead of the fastpath's 'if' check. I'd say it's a pretty small overhead -- we already optimize all other long ops, including bit inversion. |
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| msg283442 - (view) |
Author: Yury Selivanov (yselivanov) * |
Date: 2016-12-16 21:35 |
| Closing this one, as we decided to not to micro-optimize int ops. |
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