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Dictionary optimizations:

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* Factored constant structure references out of the inner loops for
  PyDict_Next(), dict_keys(), dict_values(), and dict_items().
  Gave measurable speedups to each (the improvement varies depending
  on the sparseness of the dictionary being measured).

* Added a freelist scheme styled after that for tuples.  Saves around
  80% of the calls to malloc and free.  About 10% of the time, the
  previous dictionary was completely empty; in those cases, the
  dictionary initialization with memset() can be skipped.
This commit is contained in:
Raymond Hettinger 2004-03-17 21:55:03 +00:00
parent 969d8c0c8c
commit 4344278250
1 changed files with 61 additions and 24 deletions
Download patch file Download diff file Expand all files Collapse all files

85
Objects/dictobject.c
View file

@ -152,6 +152,11 @@ show_counts(void)
INIT_NONZERO_DICT_SLOTS(mp); \
} while(0)
/* Dictionary reuse scheme to save calls to malloc, free, and memset */
#define MAXFREEDICTS 80
static PyDictObject *free_dicts[MAXFREEDICTS];
static int num_free_dicts = 0;
PyObject *
PyDict_New(void)
{
@ -164,10 +169,23 @@ PyDict_New(void)
Py_AtExit(show_counts);
#endif
}
mp = PyObject_GC_New(dictobject, &PyDict_Type);
if (mp == NULL)
return NULL;
EMPTY_TO_MINSIZE(mp);
if (num_free_dicts) {
mp = free_dicts[--num_free_dicts];
assert (mp != NULL);
assert (mp->ob_type == &PyDict_Type);
_Py_NewReference((PyObject *)mp);
if (mp->ma_fill) {
EMPTY_TO_MINSIZE(mp);
}
assert (mp->ma_used == 0);
assert (mp->ma_table == mp->ma_smalltable);
assert (mp->ma_mask == PyDict_MINSIZE - 1);
} else {
mp = PyObject_GC_New(dictobject, &PyDict_Type);
if (mp == NULL)
return NULL;
EMPTY_TO_MINSIZE(mp);
}
mp->ma_lookup = lookdict_string;
#ifdef SHOW_CONVERSION_COUNTS
++created;
@ -672,23 +690,25 @@ PyDict_Clear(PyObject *op)
int
PyDict_Next(PyObject *op, int *ppos, PyObject **pkey, PyObject **pvalue)
{
int i;
register dictobject *mp;
register int i, mask;
register dictentry *ep;
if (!PyDict_Check(op))
return 0;
mp = (dictobject *)op;
i = *ppos;
if (i < 0)
return 0;
while (i <= mp->ma_mask && mp->ma_table[i].me_value == NULL)
ep = ((dictobject *)op)->ma_table;
mask = ((dictobject *)op)->ma_mask;
while (i <= mask && ep[i].me_value == NULL)
i++;
*ppos = i+1;
if (i > mp->ma_mask)
if (i > mask)
return 0;
if (pkey)
*pkey = mp->ma_table[i].me_key;
*pkey = ep[i].me_key;
if (pvalue)
*pvalue = mp->ma_table[i].me_value;
*pvalue = ep[i].me_value;
return 1;
}
@ -710,7 +730,10 @@ dict_dealloc(register dictobject *mp)
}
if (mp->ma_table != mp->ma_smalltable)
PyMem_DEL(mp->ma_table);
mp->ob_type->tp_free((PyObject *)mp);
if (num_free_dicts < MAXFREEDICTS && mp->ob_type == &PyDict_Type)
free_dicts[num_free_dicts++] = mp;
else
mp->ob_type->tp_free((PyObject *)mp);
Py_TRASHCAN_SAFE_END(mp)
}
@ -882,7 +905,9 @@ static PyObject *
dict_keys(register dictobject *mp)
{
register PyObject *v;
register int i, j, n;
register int i, j;
dictentry *ep;
int mask, n;
again:
n = mp->ma_used;
@ -896,14 +921,17 @@ dict_keys(register dictobject *mp)
Py_DECREF(v);
goto again;
}
for (i = 0, j = 0; i <= mp->ma_mask; i++) {
if (mp->ma_table[i].me_value != NULL) {
PyObject *key = mp->ma_table[i].me_key;
ep = mp->ma_table;
mask = mp->ma_mask;
for (i = 0, j = 0; i <= mask; i++) {
if (ep[i].me_value != NULL) {
PyObject *key = ep[i].me_key;
Py_INCREF(key);
PyList_SET_ITEM(v, j, key);
j++;
}
}
assert(j == n);
return v;
}
@ -911,7 +939,9 @@ static PyObject *
dict_values(register dictobject *mp)
{
register PyObject *v;
register int i, j, n;
register int i, j;
dictentry *ep;
int mask, n;
again:
n = mp->ma_used;
@ -925,14 +955,17 @@ dict_values(register dictobject *mp)
Py_DECREF(v);
goto again;
}
for (i = 0, j = 0; i <= mp->ma_mask; i++) {
if (mp->ma_table[i].me_value != NULL) {
PyObject *value = mp->ma_table[i].me_value;
ep = mp->ma_table;
mask = mp->ma_mask;
for (i = 0, j = 0; i <= mask; i++) {
if (ep[i].me_value != NULL) {
PyObject *value = ep[i].me_value;
Py_INCREF(value);
PyList_SET_ITEM(v, j, value);
j++;
}
}
assert(j == n);
return v;
}
@ -941,7 +974,9 @@ dict_items(register dictobject *mp)
{
register PyObject *v;
register int i, j, n;
int mask;
PyObject *item, *key, *value;
dictentry *ep;
/* Preallocate the list of tuples, to avoid allocations during
* the loop over the items, which could trigger GC, which
@ -968,10 +1003,12 @@ dict_items(register dictobject *mp)
goto again;
}
/* Nothing we do below makes any function calls. */
for (i = 0, j = 0; i <= mp->ma_mask; i++) {
if (mp->ma_table[i].me_value != NULL) {
key = mp->ma_table[i].me_key;
value = mp->ma_table[i].me_value;
ep = mp->ma_table;
mask = mp->ma_mask;
for (i = 0, j = 0; i <= mask; i++) {
if (ep[i].me_value != NULL) {
key = ep[i].me_key;
value = ep[i].me_value;
item = PyList_GET_ITEM(v, j);
Py_INCREF(key);
PyTuple_SET_ITEM(item, 0, key);