Issue #24221: Small optimizations for heapq.
Replaces the PyList_GET_ITEM and PyList_SET_ITEM macros with normal array accesses. Replace the siftup unpredicatable branch with arithmetic. Replace the rc == -1 tests with rc < 0. Gives nicer looking assembly with both Clang and GCC-4.9. Also gives a small performance both for both.
This commit is contained in:
Raymond Hettinger
parent
35e24a50c5
commit
5cbd8331ff
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@ -72,6 +72,7 @@ PyAPI_FUNC(void) _PyList_DebugMallocStats(FILE *out);
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#define PyList_GET_ITEM(op, i) (((PyListObject *)(op))->ob_item[i])
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#define PyList_SET_ITEM(op, i, v) (((PyListObject *)(op))->ob_item[i] = (v))
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#define PyList_GET_SIZE(op) Py_SIZE(op)
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#define _PyList_ITEMS(op) (((PyListObject *)(op))->ob_item)
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#endif
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#ifdef __cplusplus
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@ -11,7 +11,7 @@ annotated by François Pinard, and converted to C by Raymond Hettinger.
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static int
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siftdown(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
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{
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PyObject *newitem, *parent;
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PyObject *newitem, *parent, **arr;
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Py_ssize_t parentpos, size;
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int cmp;
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@ -24,12 +24,13 @@ siftdown(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
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/* Follow the path to the root, moving parents down until finding
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a place newitem fits. */
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newitem = PyList_GET_ITEM(heap, pos);
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arr = _PyList_ITEMS(heap);
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newitem = arr[pos];
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while (pos > startpos) {
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parentpos = (pos - 1) >> 1;
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parent = PyList_GET_ITEM(heap, parentpos);
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parent = arr[parentpos];
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cmp = PyObject_RichCompareBool(newitem, parent, Py_LT);
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if (cmp == -1)
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if (cmp < 0)
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return -1;
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if (size != PyList_GET_SIZE(heap)) {
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PyErr_SetString(PyExc_RuntimeError,
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@ -38,10 +39,11 @@ siftdown(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
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}
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if (cmp == 0)
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break;
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parent = PyList_GET_ITEM(heap, parentpos);
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newitem = PyList_GET_ITEM(heap, pos);
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PyList_SET_ITEM(heap, parentpos, newitem);
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PyList_SET_ITEM(heap, pos, parent);
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arr = _PyList_ITEMS(heap);
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parent = arr[parentpos];
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newitem = arr[pos];
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arr[parentpos] = newitem;
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arr[pos] = parent;
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pos = parentpos;
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}
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return 0;
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@ -51,7 +53,7 @@ static int
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siftup(PyListObject *heap, Py_ssize_t pos)
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{
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Py_ssize_t startpos, endpos, childpos, limit;
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PyObject *tmp1, *tmp2;
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PyObject *tmp1, *tmp2, **arr;
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int cmp;
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assert(PyList_Check(heap));
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@ -63,19 +65,19 @@ siftup(PyListObject *heap, Py_ssize_t pos)
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}
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/* Bubble up the smaller child until hitting a leaf. */
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arr = _PyList_ITEMS(heap);
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limit = endpos / 2; /* smallest pos that has no child */
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while (pos < limit) {
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/* Set childpos to index of smaller child. */
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childpos = 2*pos + 1; /* leftmost child position */
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if (childpos + 1 < endpos) {
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cmp = PyObject_RichCompareBool(
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PyList_GET_ITEM(heap, childpos),
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PyList_GET_ITEM(heap, childpos + 1),
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arr[childpos],
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arr[childpos + 1],
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Py_LT);
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if (cmp == -1)
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if (cmp < 0)
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return -1;
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if (cmp == 0)
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childpos++; /* rightmost child is smallest */
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childpos += ((unsigned)cmp ^ 1); /* increment when cmp==0 */
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if (endpos != PyList_GET_SIZE(heap)) {
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PyErr_SetString(PyExc_RuntimeError,
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"list changed size during iteration");
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@ -83,10 +85,11 @@ siftup(PyListObject *heap, Py_ssize_t pos)
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}
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}
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/* Move the smaller child up. */
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tmp1 = PyList_GET_ITEM(heap, childpos);
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tmp2 = PyList_GET_ITEM(heap, pos);
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PyList_SET_ITEM(heap, childpos, tmp2);
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PyList_SET_ITEM(heap, pos, tmp1);
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arr = _PyList_ITEMS(heap);
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tmp1 = arr[childpos];
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tmp2 = arr[pos];
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arr[childpos] = tmp2;
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arr[pos] = tmp1;
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pos = childpos;
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}
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/* Bubble it up to its final resting place (by sifting its parents down). */
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@ -227,7 +230,7 @@ heappushpop(PyObject *self, PyObject *args)
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}
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cmp = PyObject_RichCompareBool(PyList_GET_ITEM(heap, 0), item, Py_LT);
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if (cmp == -1)
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if (cmp < 0)
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return NULL;
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if (cmp == 0) {
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Py_INCREF(item);
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@ -362,7 +365,7 @@ PyDoc_STRVAR(heapify_doc,
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static int
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siftdown_max(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
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{
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PyObject *newitem, *parent;
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PyObject *newitem, *parent, **arr;
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Py_ssize_t parentpos, size;
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int cmp;
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@ -375,12 +378,13 @@ siftdown_max(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
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/* Follow the path to the root, moving parents down until finding
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a place newitem fits. */
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newitem = PyList_GET_ITEM(heap, pos);
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arr = _PyList_ITEMS(heap);
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newitem = arr[pos];
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while (pos > startpos) {
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parentpos = (pos - 1) >> 1;
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parent = PyList_GET_ITEM(heap, parentpos);
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parent = arr[parentpos];
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cmp = PyObject_RichCompareBool(parent, newitem, Py_LT);
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if (cmp == -1)
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if (cmp < 0)
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return -1;
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if (size != PyList_GET_SIZE(heap)) {
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PyErr_SetString(PyExc_RuntimeError,
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@ -389,10 +393,11 @@ siftdown_max(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
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}
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if (cmp == 0)
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break;
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parent = PyList_GET_ITEM(heap, parentpos);
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newitem = PyList_GET_ITEM(heap, pos);
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PyList_SET_ITEM(heap, parentpos, newitem);
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PyList_SET_ITEM(heap, pos, parent);
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arr = _PyList_ITEMS(heap);
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parent = arr[parentpos];
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newitem = arr[pos];
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arr[parentpos] = newitem;
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arr[pos] = parent;
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pos = parentpos;
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}
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return 0;
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@ -402,7 +407,7 @@ static int
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siftup_max(PyListObject *heap, Py_ssize_t pos)
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{
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Py_ssize_t startpos, endpos, childpos, limit;
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PyObject *tmp1, *tmp2;
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PyObject *tmp1, *tmp2, **arr;
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int cmp;
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assert(PyList_Check(heap));
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@ -414,19 +419,19 @@ siftup_max(PyListObject *heap, Py_ssize_t pos)
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}
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/* Bubble up the smaller child until hitting a leaf. */
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arr = _PyList_ITEMS(heap);
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limit = endpos / 2; /* smallest pos that has no child */
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while (pos < limit) {
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/* Set childpos to index of smaller child. */
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childpos = 2*pos + 1; /* leftmost child position */
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if (childpos + 1 < endpos) {
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cmp = PyObject_RichCompareBool(
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PyList_GET_ITEM(heap, childpos + 1),
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PyList_GET_ITEM(heap, childpos),
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arr[childpos + 1],
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arr[childpos],
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Py_LT);
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if (cmp == -1)
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if (cmp < 0)
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return -1;
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if (cmp == 0)
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childpos++; /* rightmost child is smallest */
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childpos += ((unsigned)cmp ^ 1); /* increment when cmp==0 */
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if (endpos != PyList_GET_SIZE(heap)) {
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PyErr_SetString(PyExc_RuntimeError,
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"list changed size during iteration");
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@ -434,10 +439,11 @@ siftup_max(PyListObject *heap, Py_ssize_t pos)
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}
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}
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/* Move the smaller child up. */
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tmp1 = PyList_GET_ITEM(heap, childpos);
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tmp2 = PyList_GET_ITEM(heap, pos);
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PyList_SET_ITEM(heap, childpos, tmp2);
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PyList_SET_ITEM(heap, pos, tmp1);
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arr = _PyList_ITEMS(heap);
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tmp1 = arr[childpos];
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tmp2 = arr[pos];
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arr[childpos] = tmp2;
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arr[pos] = tmp1;
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pos = childpos;
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}
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/* Bubble it up to its final resting place (by sifting its parents down). */
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