Skip to content

gh-130167: Improve speed of _pydecimal._all_zeros and _pydecimal._exact_half by replacing re #132065

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 10 commits into from
Closed

gh-130167: Improve speed of _pydecimal._all_zeros and _pydecimal._exact_half by replacing re #132065

Show file tree
Hide file tree
Changes from 6 commits
Commits
Show all changes
10 commits
Select commit Hold shift + click to select a range
1bd422a
fast compute of _all_zeroes function
Marius-Juston Apr 4, 2025
d5e634c
Added news
Marius-Juston Apr 4, 2025
7037f19
speed up for exact half
Marius-Juston Apr 4, 2025
1b34a89
updated news
Marius-Juston Apr 4, 2025
c498ae6
corrected indexing checks for exact half
Marius-Juston Apr 4, 2025
328c99b
update news performance value
Marius-Juston Apr 4, 2025
b6a8014
Update Lib/_pydecimal.py
Marius-Juston Apr 4, 2025
027d93d
Update Lib/_pydecimal.py
Marius-Juston Apr 4, 2025
34486dd
simplified and sped up _all_zeros compute
Marius-Juston Apr 4, 2025
faae133
simplified and sped up exact_half
Marius-Juston Apr 4, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
9 changes: 7 additions & 2 deletions Lib/_pydecimal.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6076,8 +6076,13 @@ def _convert_for_comparison(self, other, equality_op=False):
\Z
""", re.VERBOSE | re.IGNORECASE).match

_all_zeros = re.compile('0*$').match
_exact_half = re.compile('50*$').match
# Checks for regex 0*$
def _all_zeros(d_int,prec=0):
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Do we need the prec argument?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

yes we need it, since when it gets called in:

def _round_down(self, prec):
    """Also known as round-towards-0, truncate."""
    if _all_zeros(self._int, prec):
        return 0
    else:
        return -1

and

def _round_half_up(self, prec):
    """Rounds 5 up (away from 0)"""
    if self._int[prec] in '56789':
        return 1
    elif _all_zeros(self._int, prec):
        return 0
    else:
        return -1

they both need the argument

return '0' in d_int and d_int.endswith((len(d_int) - prec) * '0')

# Checks for regex 50*$
def _exact_half(d_int, prec=0):
return len(d_int) >= prec + 1 and d_int[prec] == '5' and d_int.endswith(max(len(d_int) - prec - 1, 0) * '0')

##### PEP3101 support functions ##############################################
# The functions in this section have little to do with the Decimal
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2025-04-04-04-07-16.gh-issue-130167.XigAlq.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Improved performance of :func:`_pydecimal._all_zeros` by an average of
~1.7x and :func:`_pydecimal._exact_half` by ~1.38x. Patch by Marius Juston
Loading