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On path with a known exact float, extract the double with a fast macro. #21072

Merged
merged 1 commit into from
Jun 23, 2020
Merged

On path with a known exact float, extract the double with a fast macro. #21072

merged 1 commit into from
Jun 23, 2020

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rhettinger
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We're already testing for an exact float, so take advantage of that information and extract the double with the fast macro.

Baseline timings

$ ./python.exe -m timeit -r 11 -s 'from math import floor' -s 'x=3.14' 'floor(x)'
10000000 loops, best of 11: 38.5 nsec per loop
$ ./python.exe -m timeit -r 11 -s 'from math import floor' -s 'x=0.0' 'floor(x)'
10000000 loops, best of 11: 38.3 nsec per loop
$ ./python.exe -m timeit -r 11 -s 'from math import floor' -s 'x=-3.14E32' 'floor(x)'
5000000 loops, best of 11: 69.3 nsec per loop
$ ./python.exe -m timeit -r 11 -s 'from math import floor' -s 'x=-323452345.14' 'floor(x)'
5000000 loops, best of 11: 53.4 nsec per loop

Timings with the patch:

$ ./python.exe -m timeit -r 11 -s 'from math import floor' -s 'x=3.14' 'floor(x)'
10000000 loops, best of 11: 36.5 nsec per loop
$ ./python.exe -m timeit -r 11 -s 'from math import floor' -s 'x=0.0' 'floor(x)'
10000000 loops, best of 11: 36.5 nsec per loop
$ ./python.exe -m timeit -r 11 -s 'from math import floor' -s 'x=-3.14E32' 'floor(x)'
5000000 loops, best of 11: 64.4 nsec per loop
$ ./python.exe -m timeit -r 11 -s 'from math import floor' -s 'x=-323452345.14' 'floor(x)'
5000000 loops, best of 11: 47 nsec per loop

While the timings all show improvements, I don't understand why the timings for floor() also depend on the magnitude of the inputs.

@rhettinger rhettinger added performance Performance or resource usage skip issue skip news needs backport to 3.9 only security fixes labels Jun 23, 2020
@rhettinger rhettinger requested a review from tim-one June 23, 2020 12:10
tim-one
tim-one approved these changes Jun 23, 2020
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I don't know why, but Python 3 changed math.floor() to return an int instead of a float - so the larger the absolute value, the more time it takes to create an ever-larger int object. So it's not surprising that the time depends on the magnitude of the argument. I suppose PyLong_FromDouble() could be micro-optimized to exploit that, eventually, the trailing bits of the potentially giant int must all be 0.

>>> math.floor(3.14e32)
314000000000000005680822245916672

@rhettinger rhettinger merged commit 930f451 into python:master Jun 23, 2020
@miss-islington
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Thanks @rhettinger for the PR 🌮🎉.. I'm working now to backport this PR to: 3.9.
🐍🍒⛏🤖

@miss-islington
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Sorry @rhettinger, I had trouble checking out the 3.9 backport branch.
Please backport using cherry_picker on command line.
cherry_picker 930f4518aea7f3f0f914ce93c3fb92831a7e1d2a 3.9

@rhettinger rhettinger added needs backport to 3.9 only security fixes and removed needs backport to 3.9 only security fixes labels Jun 23, 2020
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Thanks @rhettinger for the PR 🌮🎉.. I'm working now to backport this PR to: 3.9.
🐍🍒⛏🤖

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Jun 23, 2020
@rhettinger @miss-islington
On path with known exact float, extract the double with the fast macr…
caa9486 
…o. (pythonGH-21072)

(cherry picked from commit 930f451)

Co-authored-by: Raymond Hettinger <rhettinger@users.noreply.github.com>
@bedevere-bot
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GH-21102 is a backport of this pull request to the 3.9 branch.

@bedevere-bot bedevere-bot removed the needs backport to 3.9 only security fixes label Jun 23, 2020
fasih pushed a commit to fasih/cpython that referenced this pull request Jun 29, 2020
@rhettinger @fasihahmad
On path with known exact float, extract the double with the fast macr…
321eab5 
…o. (pythonGH-21072)
arun-mani-j pushed a commit to arun-mani-j/cpython that referenced this pull request Jul 21, 2020
@rhettinger @arun-mani-j
On path with known exact float, extract the double with the fast macr…
1e8df02 
…o. (pythonGH-21072)
@Mariatta Mariatta added the needs backport to 3.9 only security fixes label Sep 4, 2020
@miss-islington
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Thanks @rhettinger for the PR 🌮🎉.. I'm working now to backport this PR to: 3.9.
🐍🍒⛏🤖

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Sep 4, 2020
@rhettinger @miss-islington
On path with known exact float, extract the double with the fast macr…
b0fe81a 
…o. (pythonGH-21072)

(cherry picked from commit 930f451)

Co-authored-by: Raymond Hettinger <rhettinger@users.noreply.github.com>
@bedevere-bot
Copy link

GH-22108 is a backport of this pull request to the 3.9 branch.

@bedevere-bot bedevere-bot removed the needs backport to 3.9 only security fixes label Sep 4, 2020
miss-islington added a commit that referenced this pull request Sep 4, 2020
@miss-islington @rhettinger
On path with known exact float, extract the double with the fast macr…
242eac1 
…o. (GH-21072)

(cherry picked from commit 930f451)

Co-authored-by: Raymond Hettinger <rhettinger@users.noreply.github.com>
@hauntsaninja hauntsaninja mentioned this pull request Sep 2, 2023
Merged
hauntsaninja added a commit to hauntsaninja/cpython that referenced this pull request Sep 2, 2023
@hauntsaninja
Optimise math.ceil for known exact float
3166603 
This matches a similar optimisation done for math.floor in
python#21072

Before:
```
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=3.14' 'ceil(x)'
20000000 loops, best of 11: 13.3 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=0.0' 'ceil(x)'
20000000 loops, best of 11: 13.3 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-3.14E32' 'ceil(x)'
10000000 loops, best of 11: 35.3 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-323452345.14' 'ceil(x)'
10000000 loops, best of 11: 21.8 nsec per loop
```

After:
```
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=3.14' 'ceil(x)'
20000000 loops, best of 11: 11.8 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=0.0' 'ceil(x)'
20000000 loops, best of 11: 11.7 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-3.14E32' 'ceil(x)'
10000000 loops, best of 11: 32.7 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-323452345.14' 'ceil(x)'
10000000 loops, best of 11: 20.1 nsec per loop
```
@hauntsaninja hauntsaninja mentioned this pull request Sep 2, 2023
Merged
hauntsaninja added a commit to hauntsaninja/cpython that referenced this pull request Sep 3, 2023
@hauntsaninja
Optimise math.ceil for known exact float
7463f3a 
This matches a similar optimisation done for math.floor in
python#21072

Before:
```
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=3.14' 'ceil(x)'
20000000 loops, best of 11: 13.3 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=0.0' 'ceil(x)'
20000000 loops, best of 11: 13.3 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-3.14E32' 'ceil(x)'
10000000 loops, best of 11: 35.3 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-323452345.14' 'ceil(x)'
10000000 loops, best of 11: 21.8 nsec per loop
```

After:
```
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=3.14' 'ceil(x)'
20000000 loops, best of 11: 11.8 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=0.0' 'ceil(x)'
20000000 loops, best of 11: 11.7 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-3.14E32' 'ceil(x)'
10000000 loops, best of 11: 32.7 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-323452345.14' 'ceil(x)'
10000000 loops, best of 11: 20.1 nsec per loop
```
@hauntsaninja hauntsaninja mentioned this pull request Oct 6, 2023
Closed
hauntsaninja added a commit that referenced this pull request Oct 6, 2023
@hauntsaninja
gh-110489: Optimise math.ceil for known exact float (#108801)
f013b47 
This matches a similar optimisation done for math.floor in
#21072
Glyphack pushed a commit to Glyphack/cpython that referenced this pull request Sep 2, 2024
@hauntsaninja @Glyphack
pythongh-110489: Optimise math.ceil for known exact float (python#108801
f02d2a7 
)

This matches a similar optimisation done for math.floor in
python#21072
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