Issue #16562: Optimize dict equality testing.

Patch by Serhiy Storchaka (reviewed by Martin and Raymond).

2 files changed, 8 insertions, 1 deletions

diff --git a/Misc/NEWS b/Misc/NEWS
index b37a3c7..f663544 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,8 @@ What's New in Python 3.4.0 Alpha 1?
 Core and Builtins
 -----------------
 
+- Issue #16562: Optimize dict equality testing.  Patch by Serhiy Storchaka.
+
 - Issue #16588: Silence unused-but-set warnings in Python/thread_pthread
 
 - Issue #16592: stringlib_bytes_join doesn't raise MemoryError on allocation
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index f4ad3dc..a3c6409 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -2114,13 +2114,18 @@ dict_equal(PyDictObject *a, PyDictObject *b)
         if (aval != NULL) {
             int cmp;
             PyObject *bval;
+            PyObject **vaddr;
             PyObject *key = ep->me_key;
             /* temporarily bump aval's refcount to ensure it stays
                alive until we're done with it */
             Py_INCREF(aval);
             /* ditto for key */
             Py_INCREF(key);
-            bval = PyDict_GetItemWithError((PyObject *)b, key);
+            /* reuse the known hash value */
+            if ((b->ma_keys->dk_lookup)(b, key, ep->me_hash, &vaddr) == NULL)
+                bval = NULL;
+            else
+                bval = *vaddr;
             Py_DECREF(key);
             if (bval == NULL) {
                 Py_DECREF(aval);