From 91c4fc45193fe3e8b83a6da88d069f15e78ac45f Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Thu, 3 Aug 2023 22:33:36 -0700
Subject: [PATCH 01/10] Use a set for TargetPython.get_tags
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This speeds up a representative pip-compile by about 40%

```
λ hyperfine -w 1 -M 3 -p 'rm req.txt || true' 'python -m piptools compile req.in --output-file req.txt --strip-extras --resolver=backtracking'
Benchmark 1: python -m piptools compile req.in --output-file req.txt --strip-extras --resolver=backtracking
  Time (mean ± σ):     28.552 s ±  2.552 s    [User: 20.477 s, System: 1.547 s]
  Range (min … max):   26.446 s … 31.390 s    3 runs

λ hyperfine -w 1 -M 3 -p 'rm req.txt || true' 'python -m piptools compile req.in --output-file req.txt --strip-extras --resolver=backtracking'
Benchmark 1: python -m piptools compile req.in --output-file req.txt --strip-extras --resolver=backtracking
  Time (mean ± σ):     17.570 s ±  0.450 s    [User: 11.537 s, System: 1.345 s]
  Range (min … max):   17.095 s … 17.989 s    3 runs
```

This makes the set.isdisjoint operation done over here much cheaper:
https://github.com/pypa/pip/blob/593b85f4a/src/pip/_internal/models/wheel.py#L92

The reason for this is because a Python usually has a lot of supported
tags. The Python I used above has 2000 supported tags! Whereas a wheel
usually only has one or two file tags.

The CPython code will unfortunately iterate over all 2000 tags to check
if there's a match. Only if the other collection is a set will CPython
think to swap the operands to iterate over the shorter collection:
https://github.com/python/cpython/blob/35963da40f/Objects/setobject.c#L1352
---
 src/pip/_internal/commands/debug.py       |  7 ++++---
 src/pip/_internal/index/package_finder.py |  2 +-
 src/pip/_internal/models/target_python.py |  8 ++++----
 src/pip/_internal/models/wheel.py         |  4 ++--
 tests/unit/test_finder.py                 | 10 +++++-----
 tests/unit/test_index.py                  |  6 +++---
 tests/unit/test_target_python.py          |  4 ++--
 7 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/src/pip/_internal/commands/debug.py b/src/pip/_internal/commands/debug.py
index 2a3e7d298f3..77713f67cde 100644
--- a/src/pip/_internal/commands/debug.py
+++ b/src/pip/_internal/commands/debug.py
@@ -5,10 +5,11 @@
 import sys
 from optparse import Values
 from types import ModuleType
-from typing import Any, Dict, List, Optional
+from typing import Any, Collection, Dict, List, Optional
 
 import pip._vendor
 from pip._vendor.certifi import where
+from pip._vendor.packaging.tags import Tag
 from pip._vendor.packaging.version import parse as parse_version
 
 from pip._internal.cli import cmdoptions
@@ -105,7 +106,7 @@ def show_tags(options: Values) -> None:
     tag_limit = 10
 
     target_python = make_target_python(options)
-    tags = target_python.get_tags()
+    tags: Collection[Tag] = target_python.get_tags()
 
     # Display the target options that were explicitly provided.
     formatted_target = target_python.format_given()
@@ -118,7 +119,7 @@ def show_tags(options: Values) -> None:
 
     if options.verbose < 1 and len(tags) > tag_limit:
         tags_limited = True
-        tags = tags[:tag_limit]
+        tags = list(tags)[:tag_limit]
     else:
         tags_limited = False
 
diff --git a/src/pip/_internal/index/package_finder.py b/src/pip/_internal/index/package_finder.py
index b6f8d57e854..2b42168da2f 100644
--- a/src/pip/_internal/index/package_finder.py
+++ b/src/pip/_internal/index/package_finder.py
@@ -428,7 +428,7 @@ def create(
     def __init__(
         self,
         project_name: str,
-        supported_tags: List[Tag],
+        supported_tags: Set[Tag],
         specifier: specifiers.BaseSpecifier,
         prefer_binary: bool = False,
         allow_all_prereleases: bool = False,
diff --git a/src/pip/_internal/models/target_python.py b/src/pip/_internal/models/target_python.py
index 744bd7ef58b..b01fd6aded1 100644
--- a/src/pip/_internal/models/target_python.py
+++ b/src/pip/_internal/models/target_python.py
@@ -1,5 +1,5 @@
 import sys
-from typing import List, Optional, Tuple
+from typing import List, Optional, Set, Tuple
 
 from pip._vendor.packaging.tags import Tag
 
@@ -62,7 +62,7 @@ def __init__(
         self.py_version_info = py_version_info
 
         # This is used to cache the return value of get_tags().
-        self._valid_tags: Optional[List[Tag]] = None
+        self._valid_tags: Optional[Set[Tag]] = None
 
     def format_given(self) -> str:
         """
@@ -84,7 +84,7 @@ def format_given(self) -> str:
             f"{key}={value!r}" for key, value in key_values if value is not None
         )
 
-    def get_tags(self) -> List[Tag]:
+    def get_tags(self) -> Set[Tag]:
         """
         Return the supported PEP 425 tags to check wheel candidates against.
 
@@ -105,6 +105,6 @@ def get_tags(self) -> List[Tag]:
                 abis=self.abis,
                 impl=self.implementation,
             )
-            self._valid_tags = tags
+            self._valid_tags = set(tags)
 
         return self._valid_tags
diff --git a/src/pip/_internal/models/wheel.py b/src/pip/_internal/models/wheel.py
index a5dc12bdd63..c05e95b1c56 100644
--- a/src/pip/_internal/models/wheel.py
+++ b/src/pip/_internal/models/wheel.py
@@ -2,7 +2,7 @@
 name that have meaning.
 """
 import re
-from typing import Dict, Iterable, List
+from typing import Dict, Iterable, List, Set
 
 from pip._vendor.packaging.tags import Tag
 
@@ -64,7 +64,7 @@ def support_index_min(self, tags: List[Tag]) -> int:
             raise ValueError()
 
     def find_most_preferred_tag(
-        self, tags: List[Tag], tag_to_priority: Dict[Tag, int]
+        self, tags: Set[Tag], tag_to_priority: Dict[Tag, int]
     ) -> int:
         """Return the priority of the most preferred tag that one of the wheel's file
         tag combinations achieves in the given list of supported tags using the given
diff --git a/tests/unit/test_finder.py b/tests/unit/test_finder.py
index 3404d1498e3..a8b608d7365 100644
--- a/tests/unit/test_finder.py
+++ b/tests/unit/test_finder.py
@@ -137,7 +137,7 @@ def test_not_find_wheel_not_supported(self, data: TestData) -> None:
         req = install_req_from_line("simple.dist")
         target_python = TargetPython()
         # Make sure no tags will match.
-        target_python._valid_tags = []
+        target_python._valid_tags = set()
         finder = make_test_finder(
             find_links=[data.find_links],
             target_python=target_python,
@@ -221,11 +221,11 @@ def test_link_sorting(self) -> None:
                 Link("simple-1.0.tar.gz"),
             ),
         ]
-        valid_tags = [
+        valid_tags = {
             Tag("pyT", "none", "TEST"),
             Tag("pyT", "TEST", "any"),
             Tag("pyT", "none", "any"),
-        ]
+        }
         specifier = SpecifierSet()
         evaluator = CandidateEvaluator(
             "my-project",
@@ -289,11 +289,11 @@ def test_build_tag_is_less_important_than_other_tags(self) -> None:
                 Link("simple-1.0.tar.gz"),
             ),
         ]
-        valid_tags = [
+        valid_tags = {
             Tag("py3", "abi3", "linux_x86_64"),
             Tag("py3", "abi3", "linux_i386"),
             Tag("py3", "any", "none"),
-        ]
+        }
         evaluator = CandidateEvaluator(
             "my-project",
             supported_tags=valid_tags,
diff --git a/tests/unit/test_index.py b/tests/unit/test_index.py
index 78837b94e8b..c83a8d30bdd 100644
--- a/tests/unit/test_index.py
+++ b/tests/unit/test_index.py
@@ -220,7 +220,7 @@ def test_evaluate_link__incompatible_wheel(self) -> None:
         """
         target_python = TargetPython(py_version_info=(3, 6, 4))
         # Set the valid tags to an empty list to make sure nothing matches.
-        target_python._valid_tags = []
+        target_python._valid_tags = set()
         evaluator = LinkEvaluator(
             project_name="sample",
             canonical_name="sample",
@@ -373,7 +373,7 @@ class TestCandidateEvaluator:
     )
     def test_create(self, allow_all_prereleases: bool, prefer_binary: bool) -> None:
         target_python = TargetPython()
-        target_python._valid_tags = [Tag("py36", "none", "any")]
+        target_python._valid_tags = {Tag("py36", "none", "any")}
         specifier = SpecifierSet()
         evaluator = CandidateEvaluator.create(
             project_name="my-project",
@@ -786,7 +786,7 @@ def test_make_candidate_evaluator(
         prefer_binary: bool,
     ) -> None:
         target_python = TargetPython()
-        target_python._valid_tags = [Tag("py36", "none", "any")]
+        target_python._valid_tags = {Tag("py36", "none", "any")}
         candidate_prefs = CandidatePreferences(
             prefer_binary=prefer_binary,
             allow_all_prereleases=allow_all_prereleases,
diff --git a/tests/unit/test_target_python.py b/tests/unit/test_target_python.py
index d3e27e39ae8..d1ed0b77cc8 100644
--- a/tests/unit/test_target_python.py
+++ b/tests/unit/test_target_python.py
@@ -116,9 +116,9 @@ def test_get_tags__uses_cached_value(self) -> None:
         Test that get_tags() uses the cached value.
         """
         target_python = TargetPython(py_version_info=None)
-        target_python._valid_tags = [
+        target_python._valid_tags = {
             Tag("py2", "none", "any"),
             Tag("py3", "none", "any"),
-        ]
+        }
         actual = target_python.get_tags()
         assert actual == [Tag("py2", "none", "any"), Tag("py3", "none", "any")]

From bcde0322bdde460f6d38b6a1ec06e01008fb2010 Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Thu, 3 Aug 2023 22:47:16 -0700
Subject: [PATCH 02/10] news

---
 news/12204.feature.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 news/12204.feature.rst

diff --git a/news/12204.feature.rst b/news/12204.feature.rst
new file mode 100644
index 00000000000..f905480d543
--- /dev/null
+++ b/news/12204.feature.rst
@@ -0,0 +1 @@
+Improve use of datastructures to speed up candidate selection by 40%

From 47f21a701d324d4beea58fff25fa5dbab18c4215 Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Thu, 3 Aug 2023 22:52:04 -0700
Subject: [PATCH 03/10] fix test

---
 tests/unit/test_target_python.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/unit/test_target_python.py b/tests/unit/test_target_python.py
index d1ed0b77cc8..e99fc2c86c8 100644
--- a/tests/unit/test_target_python.py
+++ b/tests/unit/test_target_python.py
@@ -109,7 +109,7 @@ def test_get_tags(
         assert actual == expected_version
 
         # Check that the value was cached.
-        assert target_python._valid_tags == ["tag-1", "tag-2"]
+        assert target_python._valid_tags == {"tag-1", "tag-2"}
 
     def test_get_tags__uses_cached_value(self) -> None:
         """

From c17ff03147e8524fb14c78f0f640bf04c77aef7e Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Thu, 3 Aug 2023 22:58:02 -0700
Subject: [PATCH 04/10] get_sorted_tags

---
 src/pip/_internal/commands/debug.py           |  7 +++----
 src/pip/_internal/index/package_finder.py     |  4 ++--
 src/pip/_internal/models/target_python.py     | 21 +++++++++++++++----
 .../resolution/resolvelib/factory.py          |  2 +-
 tests/unit/test_finder.py                     |  2 +-
 tests/unit/test_index.py                      |  6 +++---
 tests/unit/test_target_python.py              | 10 ++++-----
 7 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/src/pip/_internal/commands/debug.py b/src/pip/_internal/commands/debug.py
index 77713f67cde..88a4f798d46 100644
--- a/src/pip/_internal/commands/debug.py
+++ b/src/pip/_internal/commands/debug.py
@@ -5,11 +5,10 @@
 import sys
 from optparse import Values
 from types import ModuleType
-from typing import Any, Collection, Dict, List, Optional
+from typing import Any, Dict, List, Optional
 
 import pip._vendor
 from pip._vendor.certifi import where
-from pip._vendor.packaging.tags import Tag
 from pip._vendor.packaging.version import parse as parse_version
 
 from pip._internal.cli import cmdoptions
@@ -106,7 +105,7 @@ def show_tags(options: Values) -> None:
     tag_limit = 10
 
     target_python = make_target_python(options)
-    tags: Collection[Tag] = target_python.get_tags()
+    tags = target_python.get_sorted_tags()
 
     # Display the target options that were explicitly provided.
     formatted_target = target_python.format_given()
@@ -119,7 +118,7 @@ def show_tags(options: Values) -> None:
 
     if options.verbose < 1 and len(tags) > tag_limit:
         tags_limited = True
-        tags = list(tags)[:tag_limit]
+        tags = tags[:tag_limit]
     else:
         tags_limited = False
 
diff --git a/src/pip/_internal/index/package_finder.py b/src/pip/_internal/index/package_finder.py
index 2b42168da2f..5dd79682e8d 100644
--- a/src/pip/_internal/index/package_finder.py
+++ b/src/pip/_internal/index/package_finder.py
@@ -198,7 +198,7 @@ def evaluate_link(self, link: Link) -> Tuple[LinkType, str]:
                     reason = f"wrong project name (not {self.project_name})"
                     return (LinkType.different_project, reason)
 
-                supported_tags = self._target_python.get_tags()
+                supported_tags = self._target_python.get_unsorted_tags()
                 if not wheel.supported(supported_tags):
                     # Include the wheel's tags in the reason string to
                     # simplify troubleshooting compatibility issues.
@@ -414,7 +414,7 @@ def create(
         if specifier is None:
             specifier = specifiers.SpecifierSet()
 
-        supported_tags = target_python.get_tags()
+        supported_tags = target_python.get_unsorted_tags()
 
         return cls(
             project_name=project_name,
diff --git a/src/pip/_internal/models/target_python.py b/src/pip/_internal/models/target_python.py
index b01fd6aded1..16c6e5b8907 100644
--- a/src/pip/_internal/models/target_python.py
+++ b/src/pip/_internal/models/target_python.py
@@ -22,6 +22,7 @@ class TargetPython:
         "py_version",
         "py_version_info",
         "_valid_tags",
+        "_valid_tags_set",
     ]
 
     def __init__(
@@ -61,8 +62,9 @@ def __init__(
         self.py_version = py_version
         self.py_version_info = py_version_info
 
-        # This is used to cache the return value of get_tags().
-        self._valid_tags: Optional[Set[Tag]] = None
+        # This is used to cache the return value of get_(un)sorted_tags.
+        self._valid_tags: Optional[List[Tag]] = None
+        self._valid_tags_set: Optional[Set[Tag]] = None
 
     def format_given(self) -> str:
         """
@@ -84,7 +86,7 @@ def format_given(self) -> str:
             f"{key}={value!r}" for key, value in key_values if value is not None
         )
 
-    def get_tags(self) -> Set[Tag]:
+    def get_sorted_tags(self) -> List[Tag]:
         """
         Return the supported PEP 425 tags to check wheel candidates against.
 
@@ -105,6 +107,17 @@ def get_tags(self) -> Set[Tag]:
                 abis=self.abis,
                 impl=self.implementation,
             )
-            self._valid_tags = set(tags)
+            self._valid_tags = tags
 
         return self._valid_tags
+
+    def get_unsorted_tags(self) -> Set[Tag]:
+        """Exactly the same as get_sorted_tags, but returns a set.
+
+        This can be important for performance.
+        """
+        if self._valid_tags_set is None:
+            self._valid_tags_set = set(self.get_sorted_tags())
+
+        assert self._valid_tags_set is not None
+        return self._valid_tags_set
diff --git a/src/pip/_internal/resolution/resolvelib/factory.py b/src/pip/_internal/resolution/resolvelib/factory.py
index 0331297b85b..ed78580ab97 100644
--- a/src/pip/_internal/resolution/resolvelib/factory.py
+++ b/src/pip/_internal/resolution/resolvelib/factory.py
@@ -132,7 +132,7 @@ def _fail_if_link_is_unsupported_wheel(self, link: Link) -> None:
         if not link.is_wheel:
             return
         wheel = Wheel(link.filename)
-        if wheel.supported(self._finder.target_python.get_tags()):
+        if wheel.supported(self._finder.target_python.get_unsorted_tags()):
             return
         msg = f"{link.filename} is not a supported wheel on this platform."
         raise UnsupportedWheel(msg)
diff --git a/tests/unit/test_finder.py b/tests/unit/test_finder.py
index a8b608d7365..6891bc97384 100644
--- a/tests/unit/test_finder.py
+++ b/tests/unit/test_finder.py
@@ -137,7 +137,7 @@ def test_not_find_wheel_not_supported(self, data: TestData) -> None:
         req = install_req_from_line("simple.dist")
         target_python = TargetPython()
         # Make sure no tags will match.
-        target_python._valid_tags = set()
+        target_python._valid_tags = []
         finder = make_test_finder(
             find_links=[data.find_links],
             target_python=target_python,
diff --git a/tests/unit/test_index.py b/tests/unit/test_index.py
index c83a8d30bdd..78837b94e8b 100644
--- a/tests/unit/test_index.py
+++ b/tests/unit/test_index.py
@@ -220,7 +220,7 @@ def test_evaluate_link__incompatible_wheel(self) -> None:
         """
         target_python = TargetPython(py_version_info=(3, 6, 4))
         # Set the valid tags to an empty list to make sure nothing matches.
-        target_python._valid_tags = set()
+        target_python._valid_tags = []
         evaluator = LinkEvaluator(
             project_name="sample",
             canonical_name="sample",
@@ -373,7 +373,7 @@ class TestCandidateEvaluator:
     )
     def test_create(self, allow_all_prereleases: bool, prefer_binary: bool) -> None:
         target_python = TargetPython()
-        target_python._valid_tags = {Tag("py36", "none", "any")}
+        target_python._valid_tags = [Tag("py36", "none", "any")]
         specifier = SpecifierSet()
         evaluator = CandidateEvaluator.create(
             project_name="my-project",
@@ -786,7 +786,7 @@ def test_make_candidate_evaluator(
         prefer_binary: bool,
     ) -> None:
         target_python = TargetPython()
-        target_python._valid_tags = {Tag("py36", "none", "any")}
+        target_python._valid_tags = [Tag("py36", "none", "any")]
         candidate_prefs = CandidatePreferences(
             prefer_binary=prefer_binary,
             allow_all_prereleases=allow_all_prereleases,
diff --git a/tests/unit/test_target_python.py b/tests/unit/test_target_python.py
index e99fc2c86c8..04ce0dc2ffd 100644
--- a/tests/unit/test_target_python.py
+++ b/tests/unit/test_target_python.py
@@ -102,23 +102,23 @@ def test_get_tags(
         mock_get_supported.return_value = ["tag-1", "tag-2"]
 
         target_python = TargetPython(py_version_info=py_version_info)
-        actual = target_python.get_tags()
+        actual = target_python.get_sorted_tags()
         assert actual == ["tag-1", "tag-2"]
 
         actual = mock_get_supported.call_args[1]["version"]
         assert actual == expected_version
 
         # Check that the value was cached.
-        assert target_python._valid_tags == {"tag-1", "tag-2"}
+        assert target_python._valid_tags == ["tag-1", "tag-2"]
 
     def test_get_tags__uses_cached_value(self) -> None:
         """
         Test that get_tags() uses the cached value.
         """
         target_python = TargetPython(py_version_info=None)
-        target_python._valid_tags = {
+        target_python._valid_tags = [
             Tag("py2", "none", "any"),
             Tag("py3", "none", "any"),
-        }
-        actual = target_python.get_tags()
+        ]
+        actual = target_python.get_sorted_tags()
         assert actual == [Tag("py2", "none", "any"), Tag("py3", "none", "any")]

From 53f9ce7a163b5741c6669ad6a3b5c2f2d969ff49 Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Thu, 3 Aug 2023 23:11:04 -0700
Subject: [PATCH 05/10] get_unsorted_tags

---
 src/pip/_internal/models/target_python.py | 46 ++++++++++-------------
 tests/unit/test_finder.py                 |  2 +-
 tests/unit/test_index.py                  |  6 +--
 tests/unit/test_target_python.py          | 12 +++---
 4 files changed, 30 insertions(+), 36 deletions(-)

diff --git a/src/pip/_internal/models/target_python.py b/src/pip/_internal/models/target_python.py
index 16c6e5b8907..1337f758f03 100644
--- a/src/pip/_internal/models/target_python.py
+++ b/src/pip/_internal/models/target_python.py
@@ -22,7 +22,6 @@ class TargetPython:
         "py_version",
         "py_version_info",
         "_valid_tags",
-        "_valid_tags_set",
     ]
 
     def __init__(
@@ -62,9 +61,8 @@ def __init__(
         self.py_version = py_version
         self.py_version_info = py_version_info
 
-        # This is used to cache the return value of get_(un)sorted_tags.
-        self._valid_tags: Optional[List[Tag]] = None
-        self._valid_tags_set: Optional[Set[Tag]] = None
+        # This is used to cache the return value of get_unsorted_tags.
+        self._valid_tags: Optional[Set[Tag]] = None
 
     def format_given(self) -> str:
         """
@@ -92,32 +90,28 @@ def get_sorted_tags(self) -> List[Tag]:
 
         The tags are returned in order of preference (most preferred first).
         """
-        if self._valid_tags is None:
-            # Pass versions=None if no py_version_info was given since
-            # versions=None uses special default logic.
-            py_version_info = self._given_py_version_info
-            if py_version_info is None:
-                version = None
-            else:
-                version = version_info_to_nodot(py_version_info)
-
-            tags = get_supported(
-                version=version,
-                platforms=self.platforms,
-                abis=self.abis,
-                impl=self.implementation,
-            )
-            self._valid_tags = tags
+        # Pass versions=None if no py_version_info was given since
+        # versions=None uses special default logic.
+        py_version_info = self._given_py_version_info
+        if py_version_info is None:
+            version = None
+        else:
+            version = version_info_to_nodot(py_version_info)
 
-        return self._valid_tags
+        tags = get_supported(
+            version=version,
+            platforms=self.platforms,
+            abis=self.abis,
+            impl=self.implementation,
+        )
+        return tags
 
     def get_unsorted_tags(self) -> Set[Tag]:
         """Exactly the same as get_sorted_tags, but returns a set.
 
-        This can be important for performance.
+        This is important for performance.
         """
-        if self._valid_tags_set is None:
-            self._valid_tags_set = set(self.get_sorted_tags())
+        if self._valid_tags is None:
+            self._valid_tags = set(self.get_sorted_tags())
 
-        assert self._valid_tags_set is not None
-        return self._valid_tags_set
+        return self._valid_tags
diff --git a/tests/unit/test_finder.py b/tests/unit/test_finder.py
index 6891bc97384..a8b608d7365 100644
--- a/tests/unit/test_finder.py
+++ b/tests/unit/test_finder.py
@@ -137,7 +137,7 @@ def test_not_find_wheel_not_supported(self, data: TestData) -> None:
         req = install_req_from_line("simple.dist")
         target_python = TargetPython()
         # Make sure no tags will match.
-        target_python._valid_tags = []
+        target_python._valid_tags = set()
         finder = make_test_finder(
             find_links=[data.find_links],
             target_python=target_python,
diff --git a/tests/unit/test_index.py b/tests/unit/test_index.py
index 78837b94e8b..c83a8d30bdd 100644
--- a/tests/unit/test_index.py
+++ b/tests/unit/test_index.py
@@ -220,7 +220,7 @@ def test_evaluate_link__incompatible_wheel(self) -> None:
         """
         target_python = TargetPython(py_version_info=(3, 6, 4))
         # Set the valid tags to an empty list to make sure nothing matches.
-        target_python._valid_tags = []
+        target_python._valid_tags = set()
         evaluator = LinkEvaluator(
             project_name="sample",
             canonical_name="sample",
@@ -373,7 +373,7 @@ class TestCandidateEvaluator:
     )
     def test_create(self, allow_all_prereleases: bool, prefer_binary: bool) -> None:
         target_python = TargetPython()
-        target_python._valid_tags = [Tag("py36", "none", "any")]
+        target_python._valid_tags = {Tag("py36", "none", "any")}
         specifier = SpecifierSet()
         evaluator = CandidateEvaluator.create(
             project_name="my-project",
@@ -786,7 +786,7 @@ def test_make_candidate_evaluator(
         prefer_binary: bool,
     ) -> None:
         target_python = TargetPython()
-        target_python._valid_tags = [Tag("py36", "none", "any")]
+        target_python._valid_tags = {Tag("py36", "none", "any")}
         candidate_prefs = CandidatePreferences(
             prefer_binary=prefer_binary,
             allow_all_prereleases=allow_all_prereleases,
diff --git a/tests/unit/test_target_python.py b/tests/unit/test_target_python.py
index 04ce0dc2ffd..cf28ba4da99 100644
--- a/tests/unit/test_target_python.py
+++ b/tests/unit/test_target_python.py
@@ -93,7 +93,7 @@ def test_format_given(self, kwargs: Dict[str, Any], expected: str) -> None:
         ],
     )
     @mock.patch("pip._internal.models.target_python.get_supported")
-    def test_get_tags(
+    def test_get_sorted_tags(
         self,
         mock_get_supported: mock.Mock,
         py_version_info: Optional[Tuple[int, ...]],
@@ -111,14 +111,14 @@ def test_get_tags(
         # Check that the value was cached.
         assert target_python._valid_tags == ["tag-1", "tag-2"]
 
-    def test_get_tags__uses_cached_value(self) -> None:
+    def test_get_unsorted_tags__uses_cached_value(self) -> None:
         """
         Test that get_tags() uses the cached value.
         """
         target_python = TargetPython(py_version_info=None)
-        target_python._valid_tags = [
+        target_python._valid_tags = {
             Tag("py2", "none", "any"),
             Tag("py3", "none", "any"),
-        ]
-        actual = target_python.get_sorted_tags()
-        assert actual == [Tag("py2", "none", "any"), Tag("py3", "none", "any")]
+        }
+        actual = target_python.get_unsorted_tags()
+        assert actual == {Tag("py2", "none", "any"), Tag("py3", "none", "any")}

From a0c804f1581416c777cfe957c9caea11e80c52b1 Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Thu, 3 Aug 2023 23:12:33 -0700
Subject: [PATCH 06/10] test failure

---
 tests/unit/test_index.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tests/unit/test_index.py b/tests/unit/test_index.py
index c83a8d30bdd..04e7cbd4b4d 100644
--- a/tests/unit/test_index.py
+++ b/tests/unit/test_index.py
@@ -385,14 +385,14 @@ def test_create(self, allow_all_prereleases: bool, prefer_binary: bool) -> None:
         assert evaluator._allow_all_prereleases == allow_all_prereleases
         assert evaluator._prefer_binary == prefer_binary
         assert evaluator._specifier is specifier
-        assert evaluator._supported_tags == [Tag("py36", "none", "any")]
+        assert evaluator._supported_tags == {Tag("py36", "none", "any")}
 
     def test_create__target_python_none(self) -> None:
         """
         Test passing target_python=None.
         """
         evaluator = CandidateEvaluator.create("my-project")
-        expected_tags = get_supported()
+        expected_tags = set(get_supported())
         assert evaluator._supported_tags == expected_tags
 
     def test_create__specifier_none(self) -> None:
@@ -815,7 +815,7 @@ def test_make_candidate_evaluator(
         assert evaluator._prefer_binary == prefer_binary
         assert evaluator._project_name == "my-project"
         assert evaluator._specifier is specifier
-        assert evaluator._supported_tags == [Tag("py36", "none", "any")]
+        assert evaluator._supported_tags == {Tag("py36", "none", "any")}
 
 
 @pytest.mark.parametrize(

From ba7863d2e8e0d4efb029ff56fbf031729e9a438d Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Thu, 3 Aug 2023 23:20:08 -0700
Subject: [PATCH 07/10] remove caching test

---
 tests/unit/test_target_python.py | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/tests/unit/test_target_python.py b/tests/unit/test_target_python.py
index cf28ba4da99..64a3b8043e3 100644
--- a/tests/unit/test_target_python.py
+++ b/tests/unit/test_target_python.py
@@ -108,9 +108,6 @@ def test_get_sorted_tags(
         actual = mock_get_supported.call_args[1]["version"]
         assert actual == expected_version
 
-        # Check that the value was cached.
-        assert target_python._valid_tags == ["tag-1", "tag-2"]
-
     def test_get_unsorted_tags__uses_cached_value(self) -> None:
         """
         Test that get_tags() uses the cached value.

From f8fbbb1221797fa32bc8e819232657b0957de765 Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Thu, 3 Aug 2023 23:25:44 -0700
Subject: [PATCH 08/10] fix ordering

---
 src/pip/_internal/index/package_finder.py |  4 +--
 src/pip/_internal/models/target_python.py | 43 +++++++++++++----------
 src/pip/_internal/models/wheel.py         |  2 +-
 tests/unit/test_finder.py                 | 10 +++---
 tests/unit/test_index.py                  | 12 +++----
 tests/unit/test_target_python.py          |  5 ++-
 6 files changed, 42 insertions(+), 34 deletions(-)

diff --git a/src/pip/_internal/index/package_finder.py b/src/pip/_internal/index/package_finder.py
index 5dd79682e8d..2121ca327e6 100644
--- a/src/pip/_internal/index/package_finder.py
+++ b/src/pip/_internal/index/package_finder.py
@@ -414,7 +414,7 @@ def create(
         if specifier is None:
             specifier = specifiers.SpecifierSet()
 
-        supported_tags = target_python.get_unsorted_tags()
+        supported_tags = target_python.get_sorted_tags()
 
         return cls(
             project_name=project_name,
@@ -428,7 +428,7 @@ def create(
     def __init__(
         self,
         project_name: str,
-        supported_tags: Set[Tag],
+        supported_tags: List[Tag],
         specifier: specifiers.BaseSpecifier,
         prefer_binary: bool = False,
         allow_all_prereleases: bool = False,
diff --git a/src/pip/_internal/models/target_python.py b/src/pip/_internal/models/target_python.py
index 1337f758f03..67ea5da73a5 100644
--- a/src/pip/_internal/models/target_python.py
+++ b/src/pip/_internal/models/target_python.py
@@ -22,6 +22,7 @@ class TargetPython:
         "py_version",
         "py_version_info",
         "_valid_tags",
+        "_valid_tags_set",
     ]
 
     def __init__(
@@ -61,8 +62,9 @@ def __init__(
         self.py_version = py_version
         self.py_version_info = py_version_info
 
-        # This is used to cache the return value of get_unsorted_tags.
-        self._valid_tags: Optional[Set[Tag]] = None
+        # This is used to cache the return value of get_(un)sorted_tags.
+        self._valid_tags: Optional[List[Tag]] = None
+        self._valid_tags_set: Optional[Set[Tag]] = None
 
     def format_given(self) -> str:
         """
@@ -90,28 +92,31 @@ def get_sorted_tags(self) -> List[Tag]:
 
         The tags are returned in order of preference (most preferred first).
         """
-        # Pass versions=None if no py_version_info was given since
-        # versions=None uses special default logic.
-        py_version_info = self._given_py_version_info
-        if py_version_info is None:
-            version = None
-        else:
-            version = version_info_to_nodot(py_version_info)
+        if self._valid_tags is None:
+            # Pass versions=None if no py_version_info was given since
+            # versions=None uses special default logic.
+            py_version_info = self._given_py_version_info
+            if py_version_info is None:
+                version = None
+            else:
+                version = version_info_to_nodot(py_version_info)
+
+            tags = get_supported(
+                version=version,
+                platforms=self.platforms,
+                abis=self.abis,
+                impl=self.implementation,
+            )
+            self._valid_tags = tags
 
-        tags = get_supported(
-            version=version,
-            platforms=self.platforms,
-            abis=self.abis,
-            impl=self.implementation,
-        )
-        return tags
+        return self._valid_tags
 
     def get_unsorted_tags(self) -> Set[Tag]:
         """Exactly the same as get_sorted_tags, but returns a set.
 
         This is important for performance.
         """
-        if self._valid_tags is None:
-            self._valid_tags = set(self.get_sorted_tags())
+        if self._valid_tags_set is None:
+            self._valid_tags_set = set(self.get_sorted_tags())
 
-        return self._valid_tags
+        return self._valid_tags_set
diff --git a/src/pip/_internal/models/wheel.py b/src/pip/_internal/models/wheel.py
index c05e95b1c56..74beb517093 100644
--- a/src/pip/_internal/models/wheel.py
+++ b/src/pip/_internal/models/wheel.py
@@ -64,7 +64,7 @@ def support_index_min(self, tags: List[Tag]) -> int:
             raise ValueError()
 
     def find_most_preferred_tag(
-        self, tags: Set[Tag], tag_to_priority: Dict[Tag, int]
+        self, tags: List[Tag], tag_to_priority: Dict[Tag, int]
     ) -> int:
         """Return the priority of the most preferred tag that one of the wheel's file
         tag combinations achieves in the given list of supported tags using the given
diff --git a/tests/unit/test_finder.py b/tests/unit/test_finder.py
index a8b608d7365..3404d1498e3 100644
--- a/tests/unit/test_finder.py
+++ b/tests/unit/test_finder.py
@@ -137,7 +137,7 @@ def test_not_find_wheel_not_supported(self, data: TestData) -> None:
         req = install_req_from_line("simple.dist")
         target_python = TargetPython()
         # Make sure no tags will match.
-        target_python._valid_tags = set()
+        target_python._valid_tags = []
         finder = make_test_finder(
             find_links=[data.find_links],
             target_python=target_python,
@@ -221,11 +221,11 @@ def test_link_sorting(self) -> None:
                 Link("simple-1.0.tar.gz"),
             ),
         ]
-        valid_tags = {
+        valid_tags = [
             Tag("pyT", "none", "TEST"),
             Tag("pyT", "TEST", "any"),
             Tag("pyT", "none", "any"),
-        }
+        ]
         specifier = SpecifierSet()
         evaluator = CandidateEvaluator(
             "my-project",
@@ -289,11 +289,11 @@ def test_build_tag_is_less_important_than_other_tags(self) -> None:
                 Link("simple-1.0.tar.gz"),
             ),
         ]
-        valid_tags = {
+        valid_tags = [
             Tag("py3", "abi3", "linux_x86_64"),
             Tag("py3", "abi3", "linux_i386"),
             Tag("py3", "any", "none"),
-        }
+        ]
         evaluator = CandidateEvaluator(
             "my-project",
             supported_tags=valid_tags,
diff --git a/tests/unit/test_index.py b/tests/unit/test_index.py
index 04e7cbd4b4d..78837b94e8b 100644
--- a/tests/unit/test_index.py
+++ b/tests/unit/test_index.py
@@ -220,7 +220,7 @@ def test_evaluate_link__incompatible_wheel(self) -> None:
         """
         target_python = TargetPython(py_version_info=(3, 6, 4))
         # Set the valid tags to an empty list to make sure nothing matches.
-        target_python._valid_tags = set()
+        target_python._valid_tags = []
         evaluator = LinkEvaluator(
             project_name="sample",
             canonical_name="sample",
@@ -373,7 +373,7 @@ class TestCandidateEvaluator:
     )
     def test_create(self, allow_all_prereleases: bool, prefer_binary: bool) -> None:
         target_python = TargetPython()
-        target_python._valid_tags = {Tag("py36", "none", "any")}
+        target_python._valid_tags = [Tag("py36", "none", "any")]
         specifier = SpecifierSet()
         evaluator = CandidateEvaluator.create(
             project_name="my-project",
@@ -385,14 +385,14 @@ def test_create(self, allow_all_prereleases: bool, prefer_binary: bool) -> None:
         assert evaluator._allow_all_prereleases == allow_all_prereleases
         assert evaluator._prefer_binary == prefer_binary
         assert evaluator._specifier is specifier
-        assert evaluator._supported_tags == {Tag("py36", "none", "any")}
+        assert evaluator._supported_tags == [Tag("py36", "none", "any")]
 
     def test_create__target_python_none(self) -> None:
         """
         Test passing target_python=None.
         """
         evaluator = CandidateEvaluator.create("my-project")
-        expected_tags = set(get_supported())
+        expected_tags = get_supported()
         assert evaluator._supported_tags == expected_tags
 
     def test_create__specifier_none(self) -> None:
@@ -786,7 +786,7 @@ def test_make_candidate_evaluator(
         prefer_binary: bool,
     ) -> None:
         target_python = TargetPython()
-        target_python._valid_tags = {Tag("py36", "none", "any")}
+        target_python._valid_tags = [Tag("py36", "none", "any")]
         candidate_prefs = CandidatePreferences(
             prefer_binary=prefer_binary,
             allow_all_prereleases=allow_all_prereleases,
@@ -815,7 +815,7 @@ def test_make_candidate_evaluator(
         assert evaluator._prefer_binary == prefer_binary
         assert evaluator._project_name == "my-project"
         assert evaluator._specifier is specifier
-        assert evaluator._supported_tags == {Tag("py36", "none", "any")}
+        assert evaluator._supported_tags == [Tag("py36", "none", "any")]
 
 
 @pytest.mark.parametrize(
diff --git a/tests/unit/test_target_python.py b/tests/unit/test_target_python.py
index 64a3b8043e3..f14d599f1f1 100644
--- a/tests/unit/test_target_python.py
+++ b/tests/unit/test_target_python.py
@@ -108,12 +108,15 @@ def test_get_sorted_tags(
         actual = mock_get_supported.call_args[1]["version"]
         assert actual == expected_version
 
+        # Check that the value was cached.
+        assert target_python._valid_tags == ["tag-1", "tag-2"]
+
     def test_get_unsorted_tags__uses_cached_value(self) -> None:
         """
         Test that get_tags() uses the cached value.
         """
         target_python = TargetPython(py_version_info=None)
-        target_python._valid_tags = {
+        target_python._valid_tags_set = {
             Tag("py2", "none", "any"),
             Tag("py3", "none", "any"),
         }

From 18926cb32c23d017fd8793d6ea47b9b1b66f5682 Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Thu, 3 Aug 2023 23:35:03 -0700
Subject: [PATCH 09/10] delint

---
 src/pip/_internal/models/wheel.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/pip/_internal/models/wheel.py b/src/pip/_internal/models/wheel.py
index 74beb517093..a5dc12bdd63 100644
--- a/src/pip/_internal/models/wheel.py
+++ b/src/pip/_internal/models/wheel.py
@@ -2,7 +2,7 @@
 name that have meaning.
 """
 import re
-from typing import Dict, Iterable, List, Set
+from typing import Dict, Iterable, List
 
 from pip._vendor.packaging.tags import Tag
 

From dfdf4ec6a401310c6f42c00bef81fdad0196da16 Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Fri, 4 Aug 2023 01:35:11 -0700
Subject: [PATCH 10/10] fix nits

---
 news/12204.feature.rst           | 2 +-
 tests/unit/test_target_python.py | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/news/12204.feature.rst b/news/12204.feature.rst
index f905480d543..6ffdf5123b1 100644
--- a/news/12204.feature.rst
+++ b/news/12204.feature.rst
@@ -1 +1 @@
-Improve use of datastructures to speed up candidate selection by 40%
+Improve use of datastructures to make candidate selection 1.6x faster
diff --git a/tests/unit/test_target_python.py b/tests/unit/test_target_python.py
index f14d599f1f1..b659c61fe08 100644
--- a/tests/unit/test_target_python.py
+++ b/tests/unit/test_target_python.py
@@ -88,7 +88,7 @@ def test_format_given(self, kwargs: Dict[str, Any], expected: str) -> None:
             ((3, 7, 3), "37"),
             # Check a minor version with two digits.
             ((3, 10, 1), "310"),
-            # Check that versions=None is passed to get_tags().
+            # Check that versions=None is passed to get_sorted_tags().
             (None, None),
         ],
     )
@@ -113,7 +113,7 @@ def test_get_sorted_tags(
 
     def test_get_unsorted_tags__uses_cached_value(self) -> None:
         """
-        Test that get_tags() uses the cached value.
+        Test that get_unsorted_tags() uses the cached value.
         """
         target_python = TargetPython(py_version_info=None)
         target_python._valid_tags_set = {