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gh-96538: Move some type-checking out of bisect loops #96539

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Merged
merged 5 commits into from
Sep 5, 2022
Merged

gh-96538: Move some type-checking out of bisect loops #96539

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f079ac0
Move some type-checking out of bisect loops
sweeneyde Sep 3, 2022
2cfc70a
📜🤖 Added by blurb_it.
blurb-it[bot] Sep 3, 2022
b85a132
XDECREF in error label
sweeneyde Sep 3, 2022
775708f
improve comment
sweeneyde Sep 3, 2022
083f0d7
Add comments distinguishing fast path from defualt path
sweeneyde Sep 4, 2022
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2022-09-03-18-39-05.gh-issue-96538.W156-D.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Speed up ``bisect.bisect()`` functions by taking advantage of type-stability.
158 changes: 142 additions & 16 deletions Modules/_bisectmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,26 @@ get_bisect_state(PyObject *module)
return (bisect_state *)state;
}

static ssizeargfunc
get_sq_item(PyObject *s)
{
// The parts of PySequence_GetItem that we only need to do once
PyTypeObject *tp = Py_TYPE(s);
PySequenceMethods *m = tp->tp_as_sequence;
if (m && m->sq_item) {
return m->sq_item;
}
const char *msg;
if (tp->tp_as_mapping && tp->tp_as_mapping->mp_subscript) {
msg = "%.200s is not a sequence";
}
else {
msg = "'%.200s' object does not support indexing";
}
PyErr_Format(PyExc_TypeError, msg, tp->tp_name);
return NULL;
}

static inline Py_ssize_t
internal_bisect_right(PyObject *list, PyObject *item, Py_ssize_t lo, Py_ssize_t hi,
PyObject* key)
Expand All @@ -42,32 +62,85 @@ internal_bisect_right(PyObject *list, PyObject *item, Py_ssize_t lo, Py_ssize_t
if (hi < 0)
return -1;
}
ssizeargfunc sq_item = get_sq_item(list);
if (sq_item == NULL) {
return -1;
}
if (Py_EnterRecursiveCall("in _bisect.bisect_right") < 0) {
return -1;
}
PyTypeObject *tp = Py_TYPE(item);
richcmpfunc compare = tp->tp_richcompare;
while (lo < hi) {
/* The (size_t)cast ensures that the addition and subsequent division
are performed as unsigned operations, avoiding difficulties from
signed overflow. (See issue 13496.) */
mid = ((size_t)lo + hi) / 2;
litem = PySequence_GetItem(list, mid);
if (litem == NULL)
return -1;
assert(mid >= 0);
// PySequence_GetItem, but we already checked the types.
litem = sq_item(list, mid);
assert((PyErr_Occurred() == NULL) ^ (litem == NULL));
if (litem == NULL) {
goto error;
}
if (key != Py_None) {
PyObject *newitem = PyObject_CallOneArg(key, litem);
if (newitem == NULL) {
Py_DECREF(litem);
return -1;
goto error;
}
Py_SETREF(litem, newitem);
}
res = PyObject_RichCompareBool(item, litem, Py_LT);
/* if item < key(list[mid]):
* hi = mid
* else:
* lo = mid + 1
*/
if (compare != NULL && Py_IS_TYPE(litem, tp)) {
// A fast path for comparing objects of the same type
PyObject *res_obj = compare(item, litem, Py_LT);
if (res_obj == Py_True) {
Py_DECREF(res_obj);
Py_DECREF(litem);
hi = mid;
continue;
}
if (res_obj == Py_False) {
Py_DECREF(res_obj);
Py_DECREF(litem);
lo = mid + 1;
continue;
}
if (res_obj == NULL) {
goto error;
}
if (res_obj == Py_NotImplemented) {
Py_DECREF(res_obj);
compare = NULL;
res = PyObject_RichCompareBool(item, litem, Py_LT);
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Remark: this could technically call __lt__, __lt__, __gt__ instead of the current behavior, calling __lt__, __gt__.

This is similar to what unsafe_object_compare does though.

}
else {
res = PyObject_IsTrue(res_obj);
}
}
else {
// A default path for comparing arbitrary objects
res = PyObject_RichCompareBool(item, litem, Py_LT);
}
if (res < 0) {
goto error;
}
Py_DECREF(litem);
if (res < 0)
return -1;
if (res)
hi = mid;
else
lo = mid + 1;
}
Py_LeaveRecursiveCall();
return lo;
error:
Py_LeaveRecursiveCall();
Py_XDECREF(litem);
return -1;
}

/*[clinic input]
Expand Down Expand Up @@ -168,32 +241,85 @@ internal_bisect_left(PyObject *list, PyObject *item, Py_ssize_t lo, Py_ssize_t h
if (hi < 0)
return -1;
}
ssizeargfunc sq_item = get_sq_item(list);
if (sq_item == NULL) {
return -1;
}
if (Py_EnterRecursiveCall("in _bisect.bisect_left") < 0) {
return -1;
}
PyTypeObject *tp = Py_TYPE(item);
richcmpfunc compare = tp->tp_richcompare;
while (lo < hi) {
/* The (size_t)cast ensures that the addition and subsequent division
are performed as unsigned operations, avoiding difficulties from
signed overflow. (See issue 13496.) */
mid = ((size_t)lo + hi) / 2;
litem = PySequence_GetItem(list, mid);
if (litem == NULL)
return -1;
assert(mid >= 0);
// PySequence_GetItem, but we already checked the types.
litem = sq_item(list, mid);
assert((PyErr_Occurred() == NULL) ^ (litem == NULL));
if (litem == NULL) {
goto error;
}
if (key != Py_None) {
PyObject *newitem = PyObject_CallOneArg(key, litem);
if (newitem == NULL) {
Py_DECREF(litem);
return -1;
goto error;
}
Py_SETREF(litem, newitem);
}
res = PyObject_RichCompareBool(litem, item, Py_LT);
/* if key(list[mid]) < item:
* lo = mid + 1
* else:
* hi = mid
*/
if (compare != NULL && Py_IS_TYPE(litem, tp)) {
// A fast path for comparing objects of the same type
PyObject *res_obj = compare(litem, item, Py_LT);
if (res_obj == Py_True) {
Py_DECREF(res_obj);
Py_DECREF(litem);
lo = mid + 1;
continue;
}
if (res_obj == Py_False) {
Py_DECREF(res_obj);
Py_DECREF(litem);
hi = mid;
continue;
}
if (res_obj == NULL) {
goto error;
}
if (res_obj == Py_NotImplemented) {
Py_DECREF(res_obj);
compare = NULL;
res = PyObject_RichCompareBool(litem, item, Py_LT);
}
else {
res = PyObject_IsTrue(res_obj);
}
}
else {
// A default path for comparing arbitrary objects
res = PyObject_RichCompareBool(litem, item, Py_LT);
}
if (res < 0) {
goto error;
}
Py_DECREF(litem);
if (res < 0)
return -1;
if (res)
lo = mid + 1;
else
hi = mid;
}
Py_LeaveRecursiveCall();
return lo;
error:
Py_LeaveRecursiveCall();
Py_XDECREF(litem);
return -1;
}


Expand Down