[New-bugs-announce] [issue39737] Speed up list.__eq__ by about 6%

[Dennis Sweeney]

New submission from Dennis Sweeney <sweeney.dennis650 at gmail.com>:

The following tiny change:

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 3c39c6444b..3ac03b71d0 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2643,8 +2643,7 @@ list_richcompare(PyObject *v, PyObject *w, int op)

         Py_INCREF(vitem);
         Py_INCREF(witem);
-        int k = PyObject_RichCompareBool(vl->ob_item[i],
-                                         wl->ob_item[i], Py_EQ);
+        int k = PyObject_RichCompareBool(vitem, witem, Py_EQ);
         Py_DECREF(vitem);
         Py_DECREF(witem);
         if (k < 0)

Creates the following performance improvement:

Before:
> .\python.bat -m timeit -s "A = list(range(10**7)); B = list(range(10**7))" "A==B"
2 loops, best of 5: 134 msec per loop
> .\python.bat -m timeit -s "A = list(range(10**7)); B = list(range(10**7))" "A==B"
2 loops, best of 5: 134 msec per loop

After:
> .\python.bat -m timeit -s "A = list(range(10**7)); B = list(range(10**7))" "A==B"
2 loops, best of 5: 126 msec per loop
> .\python.bat -m timeit -s "A = list(range(10**7)); B = list(range(10**7))" "A==B"
2 loops, best of 5: 126 msec per loop

----------
components: Interpreter Core
messages: 362566
nosy: Dennis Sweeney
priority: normal
severity: normal
status: open
title: Speed up list.__eq__ by about 6%
type: performance
versions: Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue39737>
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