PERF: Increase threashold for using binary search in IndexEngine (#54746)

l3robot · phofl · web-flow · commit 48f5a961cb58 · 2023-08-26T12:12:08.000-07:00
* Increase threashold for using binary search in IndexEngine

* Add an entry to the latest whatsnew

* Improve entry in the lastest whatsnew

---------

Co-authored-by: Patrick Hoefler &lt;61934744+phofl@users.noreply.github.com&gt;
diff --git a/doc/source/whatsnew/v2.2.0.rst b/doc/source/whatsnew/v2.2.0.rst
@@ -153,7 +153,7 @@ Deprecations
 
 Performance improvements
 ~~~~~~~~~~~~~~~~~~~~~~~~
--
+- Performance improvement when indexing with more than 4 keys (:issue:`54550`)
 -
 
 .. ---------------------------------------------------------------------------
diff --git a/pandas/_libs/index.pyx b/pandas/_libs/index.pyx
@@ -375,7 +375,7 @@ cdef class IndexEngine:
         # map each starget to its position in the index
         if (
                 stargets and
-                len(stargets) < 5 and
+                len(stargets) < (n / (2 * n.bit_length())) and
                 not na_in_stargets and
                 self.is_monotonic_increasing
         ):

Original file line number	Diff line number	Diff line change
`@@ -153,7 +153,7 @@ Deprecations`
`153`	`153`
`154`	`154`	`Performance improvements`
`155`	`155`	`~~~~~~~~~~~~~~~~~~~~~~~~`
`156`		`--`
	`156`	+- Performance improvement when indexing with more than 4 keys (:issue:`54550`)
`157`	`157`	`-`
`158`	`158`
`159`	`159`	`.. ---------------------------------------------------------------------------`