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Optimize provider's is_backtrack_cause by caching resolved names #10621

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Optimize provider's is_backtrack_cause by caching resolved names #10621

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9ef97f2
Optimize provider's is_backtrack_cause by caching resolved names
jbylund Oct 27, 2021
4d1ea9b
Update news/10621.feature.rst
jbylund Oct 29, 2021
6951b9b
Move helper to go from sequence of backtrack causes to set of names
jbylund Oct 29, 2021
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1 change: 1 addition & 0 deletions news/10621.feature.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Optimize performance of conflict cause resolution while backtracking.
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26 changes: 20 additions & 6 deletions src/pip/_internal/resolution/resolvelib/provider.py
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Expand Up @@ -7,6 +7,7 @@
Iterator,
Mapping,
Sequence,
Set,
TypeVar,
Union,
)
Expand Down Expand Up @@ -75,6 +76,24 @@ def _get_with_identifier(
return default


key_to_names: Dict[int, Set[str]] = {}


def _get_causes_set(backtrack_causes: Sequence["PreferenceInformation"]) -> Set[str]:
key = id(backtrack_causes)
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@notatallshaw notatallshaw Oct 29, 2021 •
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I think the id being calculated here is the id of a list, but that list mutates:

pip/src/pip/_vendor/resolvelib/resolvers.py

Line 381 in 9ef97f2

self.state.backtrack_causes[:] = causes

So I think this is an incorrect assumption and that the backtrack causes could change in the list but your cache would not reflect that.

cached_names = key_to_names.get(key)
if cached_names is None:
key_to_names.clear()
cached_names = set()
for backtrack_cause in backtrack_causes:
cached_names.add(backtrack_cause.requirement.name)
parent = backtrack_cause.parent
if parent:
cached_names.add(parent.name)
key_to_names[key] = cached_names
return cached_names


class PipProvider(_ProviderBase):
"""Pip's provider implementation for resolvelib.

Expand Down Expand Up @@ -240,9 +259,4 @@ def get_dependencies(self, candidate: Candidate) -> Sequence[Requirement]:
def is_backtrack_cause(
identifier: str, backtrack_causes: Sequence["PreferenceInformation"]
) -> bool:
for backtrack_cause in backtrack_causes:
if identifier == backtrack_cause.requirement.name:
return True
if backtrack_cause.parent and identifier == backtrack_cause.parent.name:
return True
return False
return identifier in _get_causes_set(backtrack_causes)