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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.
pull/9921/head
Raymond Hettinger 11 years ago
parent
35e24a50c5
commit
5cbd8331ff
2 changed files with 44 additions and 37 deletions
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  1. 1
      Include/listobject.h
  2. 80
      Modules/_heapqmodule.c

1
Include/listobject.h
View File

@ -72,6 +72,7 @@ PyAPI_FUNC(void) _PyList_DebugMallocStats(FILE *out);
#define PyList_GET_ITEM(op, i) (((PyListObject *)(op))->ob_item[i])
#define PyList_SET_ITEM(op, i, v) (((PyListObject *)(op))->ob_item[i] = (v))
#define PyList_GET_SIZE(op) Py_SIZE(op)
#define _PyList_ITEMS(op) (((PyListObject *)(op))->ob_item)
#endif
#ifdef __cplusplus

80
Modules/_heapqmodule.c
View File

@ -11,7 +11,7 @@ annotated by François Pinard, and converted to C by Raymond Hettinger.
static int
siftdown(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
{
PyObject *newitem, *parent;
PyObject *newitem, *parent, **arr;
Py_ssize_t parentpos, size;
int cmp;
@ -24,12 +24,13 @@ siftdown(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
/* Follow the path to the root, moving parents down until finding
a place newitem fits. */
newitem = PyList_GET_ITEM(heap, pos);
arr = _PyList_ITEMS(heap);
newitem = arr[pos];
while (pos > startpos) {
parentpos = (pos - 1) >> 1;
parent = PyList_GET_ITEM(heap, parentpos);
parent = arr[parentpos];
cmp = PyObject_RichCompareBool(newitem, parent, Py_LT);
if (cmp == -1)
if (cmp < 0)
return -1;
if (size != PyList_GET_SIZE(heap)) {
PyErr_SetString(PyExc_RuntimeError,
@ -38,10 +39,11 @@ siftdown(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
}
if (cmp == 0)
break;
parent = PyList_GET_ITEM(heap, parentpos);
newitem = PyList_GET_ITEM(heap, pos);
PyList_SET_ITEM(heap, parentpos, newitem);
PyList_SET_ITEM(heap, pos, parent);
arr = _PyList_ITEMS(heap);
parent = arr[parentpos];
newitem = arr[pos];
arr[parentpos] = newitem;
arr[pos] = parent;
pos = parentpos;
}
return 0;
@ -51,7 +53,7 @@ static int
siftup(PyListObject *heap, Py_ssize_t pos)
{
Py_ssize_t startpos, endpos, childpos, limit;
PyObject *tmp1, *tmp2;
PyObject *tmp1, *tmp2, **arr;
int cmp;
assert(PyList_Check(heap));
@ -63,19 +65,19 @@ siftup(PyListObject *heap, Py_ssize_t pos)
}
/* Bubble up the smaller child until hitting a leaf. */
arr = _PyList_ITEMS(heap);
limit = endpos / 2; /* smallest pos that has no child */
while (pos < limit) {
/* Set childpos to index of smaller child. */
childpos = 2*pos + 1; /* leftmost child position */
if (childpos + 1 < endpos) {
cmp = PyObject_RichCompareBool(
PyList_GET_ITEM(heap, childpos),
PyList_GET_ITEM(heap, childpos + 1),
arr[childpos],
arr[childpos + 1],
Py_LT);
if (cmp == -1)
if (cmp < 0)
return -1;
if (cmp == 0)
childpos++; /* rightmost child is smallest */
childpos += ((unsigned)cmp ^ 1); /* increment when cmp==0 */
if (endpos != PyList_GET_SIZE(heap)) {
PyErr_SetString(PyExc_RuntimeError,
"list changed size during iteration");
@ -83,10 +85,11 @@ siftup(PyListObject *heap, Py_ssize_t pos)
}
}
/* Move the smaller child up. */
tmp1 = PyList_GET_ITEM(heap, childpos);
tmp2 = PyList_GET_ITEM(heap, pos);
PyList_SET_ITEM(heap, childpos, tmp2);
PyList_SET_ITEM(heap, pos, tmp1);
arr = _PyList_ITEMS(heap);
tmp1 = arr[childpos];
tmp2 = arr[pos];
arr[childpos] = tmp2;
arr[pos] = tmp1;
pos = childpos;
}
/* Bubble it up to its final resting place (by sifting its parents down). */
@ -227,7 +230,7 @@ heappushpop(PyObject *self, PyObject *args)
}
cmp = PyObject_RichCompareBool(PyList_GET_ITEM(heap, 0), item, Py_LT);
if (cmp == -1)
if (cmp < 0)
return NULL;
if (cmp == 0) {
Py_INCREF(item);
@ -362,7 +365,7 @@ PyDoc_STRVAR(heapify_doc,
static int
siftdown_max(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
{
PyObject *newitem, *parent;
PyObject *newitem, *parent, **arr;
Py_ssize_t parentpos, size;
int cmp;
@ -375,12 +378,13 @@ siftdown_max(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
/* Follow the path to the root, moving parents down until finding
a place newitem fits. */
newitem = PyList_GET_ITEM(heap, pos);
arr = _PyList_ITEMS(heap);
newitem = arr[pos];
while (pos > startpos) {
parentpos = (pos - 1) >> 1;
parent = PyList_GET_ITEM(heap, parentpos);
parent = arr[parentpos];
cmp = PyObject_RichCompareBool(parent, newitem, Py_LT);
if (cmp == -1)
if (cmp < 0)
return -1;
if (size != PyList_GET_SIZE(heap)) {
PyErr_SetString(PyExc_RuntimeError,
@ -389,10 +393,11 @@ siftdown_max(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
}
if (cmp == 0)
break;
parent = PyList_GET_ITEM(heap, parentpos);
newitem = PyList_GET_ITEM(heap, pos);
PyList_SET_ITEM(heap, parentpos, newitem);
PyList_SET_ITEM(heap, pos, parent);
arr = _PyList_ITEMS(heap);
parent = arr[parentpos];
newitem = arr[pos];
arr[parentpos] = newitem;
arr[pos] = parent;
pos = parentpos;
}
return 0;
@ -402,7 +407,7 @@ static int
siftup_max(PyListObject *heap, Py_ssize_t pos)
{
Py_ssize_t startpos, endpos, childpos, limit;
PyObject *tmp1, *tmp2;
PyObject *tmp1, *tmp2, **arr;
int cmp;
assert(PyList_Check(heap));
@ -414,19 +419,19 @@ siftup_max(PyListObject *heap, Py_ssize_t pos)
}
/* Bubble up the smaller child until hitting a leaf. */
arr = _PyList_ITEMS(heap);
limit = endpos / 2; /* smallest pos that has no child */
while (pos < limit) {
/* Set childpos to index of smaller child. */
childpos = 2*pos + 1; /* leftmost child position */
if (childpos + 1 < endpos) {
cmp = PyObject_RichCompareBool(
PyList_GET_ITEM(heap, childpos + 1),
PyList_GET_ITEM(heap, childpos),
arr[childpos + 1],
arr[childpos],
Py_LT);
if (cmp == -1)
if (cmp < 0)
return -1;
if (cmp == 0)
childpos++; /* rightmost child is smallest */
childpos += ((unsigned)cmp ^ 1); /* increment when cmp==0 */
if (endpos != PyList_GET_SIZE(heap)) {
PyErr_SetString(PyExc_RuntimeError,
"list changed size during iteration");
@ -434,10 +439,11 @@ siftup_max(PyListObject *heap, Py_ssize_t pos)
}
}
/* Move the smaller child up. */
tmp1 = PyList_GET_ITEM(heap, childpos);
tmp2 = PyList_GET_ITEM(heap, pos);
PyList_SET_ITEM(heap, childpos, tmp2);
PyList_SET_ITEM(heap, pos, tmp1);
arr = _PyList_ITEMS(heap);
tmp1 = arr[childpos];
tmp2 = arr[pos];
arr[childpos] = tmp2;
arr[pos] = tmp1;
pos = childpos;
}
/* Bubble it up to its final resting place (by sifting its parents down). */

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