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Issue #21101: Eliminate double hashing in the C code for collections.Counter().

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This commit is contained in:
Raymond Hettinger 2014-05-03 16:41:19 -07:00
parent 4b74fba62f
commit 4b0b1accb5
2 changed files with 17 additions and 3 deletions
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3
Misc/NEWS
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@ -73,6 +73,9 @@ Library
Decimal.quantize() method in the Python version. It had never been
present in the C version.
- Issue #21101: Eliminate double hashing in the C speed-up code for
collections.Counter().
- Issue #21321: itertools.islice() now releases the reference to the source
iterator when the slice is exhausted. Patch by Anton Afanasyev.

17
Modules/_collectionsmodule.c
View file

@ -1831,18 +1831,29 @@ _count_elements(PyObject *self, PyObject *args)
if (mapping_get != NULL && mapping_get == dict_get &&
mapping_setitem != NULL && mapping_setitem == dict_setitem) {
while (1) {
Py_hash_t hash;
key = PyIter_Next(it);
if (key == NULL)
break;
oldval = PyDict_GetItem(mapping, key);
if (!PyUnicode_CheckExact(key) ||
(hash = ((PyASCIIObject *) key)->hash) == -1)
{
hash = PyObject_Hash(key);
if (hash == -1)
goto done;
}
oldval = _PyDict_GetItem_KnownHash(mapping, key, hash);
if (oldval == NULL) {
if (PyDict_SetItem(mapping, key, one) == -1)
if (_PyDict_SetItem_KnownHash(mapping, key, one, hash) == -1)
break;
} else {
newval = PyNumber_Add(oldval, one);
if (newval == NULL)
break;
if (PyDict_SetItem(mapping, key, newval) == -1)
if (_PyDict_SetItem_KnownHash(mapping, key, newval, hash) == -1)
break;
Py_CLEAR(newval);
}