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tim-onetim-one
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Store the mask instead of the size in dictobjects. The mask is more
frequently used, and in particular this allows to drop the last remaining obvious time-waster in the crucial lookdict() and lookdict_string() functions. Other changes consist mostly of changing "i < ma_size" to "i <= ma_mask" everywhere.
1 parent b9d973d commit afb6ae8

1 file changed

Lines changed: 29 additions & 23 deletions

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‎Objects/dictobject.c‎

Lines changed: 29 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -162,7 +162,13 @@ struct dictobject {
162162
PyObject_HEAD
163163
int ma_fill; /* # Active + # Dummy */
164164
int ma_used; /* # Active */
165-
int ma_size; /* total # slots in ma_table */
165+
166+
/* The table contains ma_mask + 1 slots, and that's a power of 2.
167+
* We store the mask instead of the size because the mask is more
168+
* frequently needed.
169+
*/
170+
int ma_mask;
171+
166172
/* ma_table points to ma_smalltable for small tables, else to
167173
* additional malloc'ed memory. ma_table is never NULL! This rule
168174
* saves repeated runtime null-tests in the workhorse getitem and
@@ -194,7 +200,7 @@ show_counts(void)
194200
#define empty_to_minsize(mp) do { \
195201
memset((mp)->ma_smalltable, 0, sizeof((mp)->ma_smalltable)); \
196202
(mp)->ma_table = (mp)->ma_smalltable; \
197-
(mp)->ma_size = MINSIZE; \
203+
(mp)->ma_mask = MINSIZE - 1; \
198204
(mp)->ma_used = (mp)->ma_fill = 0; \
199205
} while(0)
200206

@@ -248,7 +254,7 @@ lookdict(dictobject *mp, PyObject *key, register long hash)
248254
register int i;
249255
register unsigned int perturb;
250256
register dictentry *freeslot;
251-
register unsigned int mask = mp->ma_size-1;
257+
register unsigned int mask = mp->ma_mask;
252258
dictentry *ep0 = mp->ma_table;
253259
register dictentry *ep;
254260
register int restore_error;
@@ -359,7 +365,7 @@ lookdict_string(dictobject *mp, PyObject *key, register long hash)
359365
register int i;
360366
register unsigned int perturb;
361367
register dictentry *freeslot;
362-
register unsigned int mask = mp->ma_size-1;
368+
register unsigned int mask = mp->ma_mask;
363369
dictentry *ep0 = mp->ma_table;
364370
register dictentry *ep;
365371

@@ -492,7 +498,7 @@ dictresize(dictobject *mp, int minused)
492498
/* Make the dict empty, using the new table. */
493499
assert(newtable != oldtable);
494500
mp->ma_table = newtable;
495-
mp->ma_size = newsize;
501+
mp->ma_mask = newsize - 1;
496502
memset(newtable, 0, sizeof(dictentry) * newsize);
497503
mp->ma_used = 0;
498504
i = mp->ma_fill;
@@ -580,7 +586,7 @@ PyDict_SetItem(register PyObject *op, PyObject *key, PyObject *value)
580586
if (hash == -1)
581587
return -1;
582588
}
583-
assert(mp->ma_fill < mp->ma_size);
589+
assert(mp->ma_fill <= mp->ma_mask); /* at least one empty slot */
584590
n_used = mp->ma_used;
585591
Py_INCREF(value);
586592
Py_INCREF(key);
@@ -591,7 +597,7 @@ PyDict_SetItem(register PyObject *op, PyObject *key, PyObject *value)
591597
* much larger than ma_used, meaning a lot of dict keys have been
592598
* deleted).
593599
*/
594-
if (mp->ma_used > n_used && mp->ma_fill*3 >= mp->ma_size*2) {
600+
if (mp->ma_used > n_used && mp->ma_fill*3 >= (mp->ma_mask+1)*2) {
595601
if (dictresize(mp, mp->ma_used*2) != 0)
596602
return -1;
597603
}
@@ -652,7 +658,7 @@ PyDict_Clear(PyObject *op)
652658
return;
653659
mp = (dictobject *)op;
654660
#ifdef Py_DEBUG
655-
n = mp->ma_size;
661+
n = mp->ma_mask + 1;
656662
i = 0;
657663
#endif
658664

@@ -721,10 +727,10 @@ PyDict_Next(PyObject *op, int *ppos, PyObject **pkey, PyObject **pvalue)
721727
i = *ppos;
722728
if (i < 0)
723729
return 0;
724-
while (i < mp->ma_size && mp->ma_table[i].me_value == NULL)
730+
while (i <= mp->ma_mask && mp->ma_table[i].me_value == NULL)
725731
i++;
726732
*ppos = i+1;
727-
if (i >= mp->ma_size)
733+
if (i > mp->ma_mask)
728734
return 0;
729735
if (pkey)
730736
*pkey = mp->ma_table[i].me_key;
@@ -772,7 +778,7 @@ dict_print(register dictobject *mp, register FILE *fp, register int flags)
772778

773779
fprintf(fp, "{");
774780
any = 0;
775-
for (i = 0; i < mp->ma_size; i++) {
781+
for (i = 0; i <= mp->ma_mask; i++) {
776782
dictentry *ep = mp->ma_table + i;
777783
PyObject *pvalue = ep->me_value;
778784
if (pvalue != NULL) {
@@ -819,7 +825,7 @@ dict_repr(dictobject *mp)
819825
sepa = PyString_FromString(", ");
820826
colon = PyString_FromString(": ");
821827
any = 0;
822-
for (i = 0; i < mp->ma_size && v; i++) {
828+
for (i = 0; i <= mp->ma_mask && v; i++) {
823829
dictentry *ep = mp->ma_table + i;
824830
PyObject *pvalue = ep->me_value;
825831
if (pvalue != NULL) {
@@ -905,7 +911,7 @@ dict_keys(register dictobject *mp, PyObject *args)
905911
Py_DECREF(v);
906912
goto again;
907913
}
908-
for (i = 0, j = 0; i < mp->ma_size; i++) {
914+
for (i = 0, j = 0; i <= mp->ma_mask; i++) {
909915
if (mp->ma_table[i].me_value != NULL) {
910916
PyObject *key = mp->ma_table[i].me_key;
911917
Py_INCREF(key);
@@ -936,7 +942,7 @@ dict_values(register dictobject *mp, PyObject *args)
936942
Py_DECREF(v);
937943
goto again;
938944
}
939-
for (i = 0, j = 0; i < mp->ma_size; i++) {
945+
for (i = 0, j = 0; i <= mp->ma_mask; i++) {
940946
if (mp->ma_table[i].me_value != NULL) {
941947
PyObject *value = mp->ma_table[i].me_value;
942948
Py_INCREF(value);
@@ -981,7 +987,7 @@ dict_items(register dictobject *mp, PyObject *args)
981987
goto again;
982988
}
983989
/* Nothing we do below makes any function calls. */
984-
for (i = 0, j = 0; i < mp->ma_size; i++) {
990+
for (i = 0, j = 0; i <= mp->ma_mask; i++) {
985991
if (mp->ma_table[i].me_value != NULL) {
986992
key = mp->ma_table[i].me_key;
987993
value = mp->ma_table[i].me_value;
@@ -1010,11 +1016,11 @@ dict_update(register dictobject *mp, PyObject *args)
10101016
/* Do one big resize at the start, rather than incrementally
10111017
resizing as we insert new items. Expect that there will be
10121018
no (or few) overlapping keys. */
1013-
if ((mp->ma_fill + other->ma_used)*3 >= mp->ma_size*2) {
1019+
if ((mp->ma_fill + other->ma_used)*3 >= (mp->ma_mask+1)*2) {
10141020
if (dictresize(mp, (mp->ma_used + other->ma_used)*3/2) != 0)
10151021
return NULL;
10161022
}
1017-
for (i = 0; i < other->ma_size; i++) {
1023+
for (i = 0; i <= other->ma_mask; i++) {
10181024
entry = &other->ma_table[i];
10191025
if (entry->me_value != NULL) {
10201026
Py_INCREF(entry->me_key);
@@ -1055,7 +1061,7 @@ PyDict_Copy(PyObject *o)
10551061
if (mp->ma_used > 0) {
10561062
if (dictresize(copy, mp->ma_used*3/2) != 0)
10571063
return NULL;
1058-
for (i = 0; i < mp->ma_size; i++) {
1064+
for (i = 0; i <= mp->ma_mask; i++) {
10591065
entry = &mp->ma_table[i];
10601066
if (entry->me_value != NULL) {
10611067
Py_INCREF(entry->me_key);
@@ -1123,7 +1129,7 @@ characterize(dictobject *a, dictobject *b, PyObject **pval)
11231129
PyObject *aval = NULL; /* a[akey] */
11241130
int i, cmp;
11251131

1126-
for (i = 0; i < a->ma_size; i++) {
1132+
for (i = 0; i <= a->ma_mask; i++) {
11271133
PyObject *thiskey, *thisaval, *thisbval;
11281134
if (a->ma_table[i].me_value == NULL)
11291135
continue;
@@ -1136,7 +1142,7 @@ characterize(dictobject *a, dictobject *b, PyObject **pval)
11361142
goto Fail;
11371143
}
11381144
if (cmp > 0 ||
1139-
i >= a->ma_size ||
1145+
i > a->ma_mask ||
11401146
a->ma_table[i].me_value == NULL)
11411147
{
11421148
/* Not the *smallest* a key; or maybe it is
@@ -1251,7 +1257,7 @@ dict_equal(dictobject *a, dictobject *b)
12511257
return 0;
12521258

12531259
/* Same # of entries -- check all of 'em. Exit early on any diff. */
1254-
for (i = 0; i < a->ma_size; i++) {
1260+
for (i = 0; i <= a->ma_mask; i++) {
12551261
PyObject *aval = a->ma_table[i].me_value;
12561262
if (aval != NULL) {
12571263
int cmp;
@@ -1427,11 +1433,11 @@ dict_popitem(dictobject *mp, PyObject *args)
14271433
* finger that's out of bounds now because it wrapped around
14281434
* or the table shrunk -- simply make sure it's in bounds now.
14291435
*/
1430-
if (i >= mp->ma_size || i < 1)
1436+
if (i > mp->ma_mask || i < 1)
14311437
i = 1; /* skip slot 0 */
14321438
while ((ep = &mp->ma_table[i])->me_value == NULL) {
14331439
i++;
1434-
if (i >= mp->ma_size)
1440+
if (i > mp->ma_mask)
14351441
i = 1;
14361442
}
14371443
}

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