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SF patch #687598, array.append is sloooow

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This improves speed by about 5.6% for me.
This commit is contained in:
Neal Norwitz 2003-02-24 02:08:42 +00:00
parent 577fb5a1db
commit 937ca98e34
1 changed files with 47 additions and 2 deletions
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49
Modules/arraymodule.c
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@ -13,6 +13,52 @@
#endif /* DONT_HAVE_SYS_TYPES_H */
#endif /* !STDC_HEADERS */
/* Shamelessy stolen from listobject.c */
static int
roundupsize(int n)
{
unsigned int nbits = 0;
unsigned int n2 = (unsigned int)n >> 5;
/* Round up:
* If n < 256, to a multiple of 8.
* If n < 2048, to a multiple of 64.
* If n < 16384, to a multiple of 512.
* If n < 131072, to a multiple of 4096.
* If n < 1048576, to a multiple of 32768.
* If n < 8388608, to a multiple of 262144.
* If n < 67108864, to a multiple of 2097152.
* If n < 536870912, to a multiple of 16777216.
* ...
* If n < 2**(5+3*i), to a multiple of 2**(3*i).
*
* This over-allocates proportional to the list size, making room
* for additional growth. The over-allocation is mild, but is
* enough to give linear-time amortized behavior over a long
* sequence of appends() in the presence of a poorly-performing
* system realloc() (which is a reality, e.g., across all flavors
* of Windows, with Win9x behavior being particularly bad -- and
* we've still got address space fragmentation problems on Win9x
* even with this scheme, although it requires much longer lists to
* provoke them than it used to).
*/
do {
n2 >>= 3;
nbits += 3;
} while (n2);
return ((n >> nbits) + 1) << nbits;
}
#define NRESIZE(var, type, nitems) \
do { \
size_t _new_size = roundupsize(nitems); \
if (_new_size <= ((~(size_t)0) / sizeof(type))) \
PyMem_RESIZE(var, type, _new_size); \
else \
var = NULL; \
} while (0)
/* END SHAMELESSLY STOLEN CODE */
struct arrayobject; /* Forward */
/* All possible arraydescr values are defined in the vector "descriptors"
@ -419,8 +465,7 @@ ins1(arrayobject *self, int where, PyObject *v)
if ((*self->ob_descr->setitem)(self, -1, v) < 0)
return -1;
items = self->ob_item;
PyMem_RESIZE(items, char,
(self->ob_size+1) * self->ob_descr->itemsize);
NRESIZE(items, char, (self->ob_size+1) * self->ob_descr->itemsize);
if (items == NULL) {
PyErr_NoMemory();
return -1;