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list_resize() now has an "exact" option for bypassing the overallocation 

scheme in situations that likely won't benefit from it.  This further
improves memory utilization from Py2.3 which always over-allocates
except for PyList_New().

Situations expected to benefit from over-allocation:
    list.insert(), list.pop(), list.append(), and list.extend()

Situations deemed unlikely to benefit:
    list_inplace_repeat, list_ass_slice, list_ass_subscript

The most gray area was for listextend_internal() which only runs
when the argument is a list or a tuple.  This could be viewed as
a one-time fixed length addition or it could be viewed as wrapping
a series of appends.  I left its over-allocation turned on but
could be convinced otherwise.
This commit is contained in:
Raymond Hettinger 2004-03-14 06:42:23 +00:00
parent 49f9bd15ff
commit 0e91643bd2
1 changed files with 13 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
Objects/listobject.c
View File

@ -9,7 +9,7 @@
#endif
static int
list_resize(PyListObject *self, int newsize)
list_resize(PyListObject *self, int newsize, int exact)
{
PyObject **items;
size_t _new_size;
@ -33,7 +33,10 @@ list_resize(PyListObject *self, int newsize)
* system realloc().
* The growth pattern is: 0, 4, 8, 16, 25, 35, 46, 58, 72, 88, ...
*/
_new_size = (newsize >> 3) + (self->ob_size < 8 ? 3 : 6) + newsize;
if (exact)
_new_size = newsize;
else
_new_size = (newsize>>3) + (self->ob_size < 8 ? 3 : 6) + newsize;
items = self->ob_item;
if (_new_size <= ((~(size_t)0) / sizeof(PyObject *)))
PyMem_RESIZE(items, PyObject *, _new_size);
@ -152,7 +155,7 @@ ins1(PyListObject *self, int where, PyObject *v)
return -1;
}
if (list_resize(self, n+1) == -1)
if (list_resize(self, n+1, 0) == -1)
return -1;
if (where < 0) {
@ -518,13 +521,13 @@ list_ass_slice(PyListObject *a, int ilow, int ihigh, PyObject *v)
if (d < 0) {
memmove(&item[ihigh+d], &item[ihigh],
(a->ob_size - ihigh)*sizeof(PyObject *));
list_resize(a, a->ob_size + d);
list_resize(a, a->ob_size + d, 1);
item = a->ob_item;
}
}
else { /* Insert d items; recycle ihigh-ilow items */
s = a->ob_size;
if (list_resize(a, s+d) == -1) {
if (list_resize(a, s+d, 1) == -1) {
if (recycle != NULL)
PyMem_DEL(recycle);
return -1;
@ -588,7 +591,7 @@ list_inplace_repeat(PyListObject *self, int n)
return (PyObject *)self;
}
if (list_resize(self, size*n) == -1)
if (list_resize(self, size*n, 1) == -1)
return NULL;
p = size;
@ -680,7 +683,7 @@ listextend_internal(PyListObject *self, PyObject *b)
}
}
if (list_resize(self, selflen + blen) == -1) {
if (list_resize(self, selflen + blen, 0) == -1) {
Py_DECREF(b);
return -1;
}
@ -733,7 +736,7 @@ listextend(PyListObject *self, PyObject *b)
}
m = self->ob_size;
mn = m + n;
if (list_resize(self, mn) == -1)
if (list_resize(self, mn, 0) == -1)
goto error;
memset(&(self->ob_item[m]), 0, sizeof(*self->ob_item) * n);
@ -818,7 +821,7 @@ listpop(PyListObject *self, PyObject *args)
}
v = self->ob_item[i];
if (i == self->ob_size - 1) {
if (list_resize(self, self->ob_size - 1) == -1)
if (list_resize(self, self->ob_size - 1, 0) == -1)
return NULL;
return v;
}
@ -2517,7 +2520,7 @@ list_ass_subscript(PyListObject* self, PyObject* item, PyObject* value)
}
self->ob_size -= slicelength;
list_resize(self, self->ob_size);
list_resize(self, self->ob_size, 1);
for (i = 0; i < slicelength; i++) {
Py_DECREF(garbage[i]);