Index: Objects/dictobject.c
===================================================================
--- Objects/dictobject.c	(révision 86449)
+++ Objects/dictobject.c	(copie de travail)
@@ -28,8 +28,10 @@
 /* Define this out if you don't want conversion statistics on exit. */
 #undef SHOW_CONVERSION_COUNTS
 
-/* See large comment block below.  This must be >= 1. */
-#define PERTURB_SHIFT 5
+/* Initial hash perturbation, to avoid clustering effects with the master
+   hash() function while maintaining linear probing for better cache locality
+   when collision happen. */
+#define INITIAL_HASH(mp, h) (((size_t) h * 1000003) & mp->ma_mask)
 
 /*
 Major subtleties ahead:  Most hash schemes depend on having a "good" hash
@@ -312,7 +314,6 @@
 lookdict(PyDictObject *mp, PyObject *key, register Py_hash_t hash)
 {
     register size_t i;
-    register size_t perturb;
     register PyDictEntry *freeslot;
     register size_t mask = (size_t)mp->ma_mask;
     PyDictEntry *ep0 = mp->ma_table;
@@ -320,7 +321,7 @@
     register int cmp;
     PyObject *startkey;
 
-    i = (size_t)hash & mask;
+    i = INITIAL_HASH(mp, hash);
     ep = &ep0[i];
     if (ep->me_key == NULL || ep->me_key == key)
         return ep;
@@ -353,8 +354,8 @@
 
     /* In the loop, me_key == dummy is by far (factor of 100s) the
        least likely outcome, so test for that last. */
-    for (perturb = hash; ; perturb >>= PERTURB_SHIFT) {
-        i = (i << 2) + i + perturb + 1;
+    for (;;) {
+        i = i + 1;
         ep = &ep0[i & mask];
         if (ep->me_key == NULL)
             return freeslot == NULL ? ep : freeslot;
@@ -401,7 +402,6 @@
 lookdict_unicode(PyDictObject *mp, PyObject *key, register Py_hash_t hash)
 {
     register size_t i;
-    register size_t perturb;
     register PyDictEntry *freeslot;
     register size_t mask = (size_t)mp->ma_mask;
     PyDictEntry *ep0 = mp->ma_table;
@@ -418,7 +418,7 @@
         mp->ma_lookup = lookdict;
         return lookdict(mp, key, hash);
     }
-    i = hash & mask;
+    i = INITIAL_HASH(mp, hash);
     ep = &ep0[i];
     if (ep->me_key == NULL || ep->me_key == key)
         return ep;
@@ -432,8 +432,8 @@
 
     /* In the loop, me_key == dummy is by far (factor of 100s) the
        least likely outcome, so test for that last. */
-    for (perturb = hash; ; perturb >>= PERTURB_SHIFT) {
-        i = (i << 2) + i + perturb + 1;
+    for (;;) {
+        i = i + 1;
         ep = &ep0[i & mask];
         if (ep->me_key == NULL)
             return freeslot == NULL ? ep : freeslot;
@@ -566,16 +566,15 @@
                  PyObject *value)
 {
     register size_t i;
-    register size_t perturb;
     register size_t mask = (size_t)mp->ma_mask;
     PyDictEntry *ep0 = mp->ma_table;
     register PyDictEntry *ep;
 
     MAINTAIN_TRACKING(mp, key, value);
-    i = hash & mask;
+    i = INITIAL_HASH(mp, hash);
     ep = &ep0[i];
-    for (perturb = hash; ep->me_key != NULL; perturb >>= PERTURB_SHIFT) {
-        i = (i << 2) + i + perturb + 1;
+    while (ep->me_key != NULL) {
+        i = i + 1;
         ep = &ep0[i & mask];
     }
     assert(ep->me_value == NULL);
@@ -825,7 +824,7 @@
      */
     if (!(mp->ma_used > n_used && mp->ma_fill*3 >= (mp->ma_mask+1)*2))
         return 0;
-    return dictresize(mp, (mp->ma_used > 50000 ? 2 : 4) * mp->ma_used);
+    return dictresize(mp, 2 * mp->ma_used);
 }
 
 int