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Issue #8685: Speed up set difference a - b when source set a is

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much larger than operand `b`.  Patch by Andrew Bennetts.
This commit is contained in:
Antoine Pitrou 2010-11-30 22:23:20 +00:00
parent 697ce95931
commit 715f3cd10d
2 changed files with 25 additions and 7 deletions
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3
Misc/NEWS
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@ -10,6 +10,9 @@ What's New in Python 3.2 Beta 1?
Core and Builtins
-----------------
- Issue #8685: Speed up set difference ``a - b`` when source set ``a`` is
much larger than operand ``b``. Patch by Andrew Bennetts.
- Issue #10518: Bring back the callable() builtin.
- Issue #8879. Add os.link support for Windows.

29
Objects/setobject.c
View file

@ -1524,6 +1524,20 @@ set_difference_update(PySetObject *so, PyObject *args)
PyDoc_STRVAR(difference_update_doc,
"Remove all elements of another set from this set.");
static PyObject *
set_copy_and_difference(PySetObject *so, PyObject *other)
{
PyObject *result;
result = set_copy(so);
if (result == NULL)
return NULL;
if (set_difference_update_internal((PySetObject *) result, other) != -1)
return result;
Py_DECREF(result);
return NULL;
}
static PyObject *
set_difference(PySetObject *so, PyObject *other)
{
@ -1532,13 +1546,13 @@ set_difference(PySetObject *so, PyObject *other)
Py_ssize_t pos = 0;
if (!PyAnySet_Check(other) && !PyDict_CheckExact(other)) {
result = set_copy(so);
if (result == NULL)
return NULL;
if (set_difference_update_internal((PySetObject *)result, other) != -1)
return result;
Py_DECREF(result);
return NULL;
return set_copy_and_difference(so, other);
}
/* If len(so) much more than len(other), it's more efficient to simply copy
* so and then iterate other looking for common elements. */
if ((PySet_GET_SIZE(so) >> 2) > PyObject_Size(other)) {
return set_copy_and_difference(so, other);
}
result = make_new_set_basetype(Py_TYPE(so), NULL);
@ -1560,6 +1574,7 @@ set_difference(PySetObject *so, PyObject *other)
return result;
}
/* Iterate over so, checking for common elements in other. */
while (set_next(so, &pos, &entry)) {
int rv = set_contains_entry((PySetObject *)other, entry);
if (rv == -1) {