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Issue #19581: Change the overallocation factor of _PyUnicodeWriter on Windows 

On Windows, a factor of 50% gives best performances.
This commit is contained in:
Victor Stinner 2013-11-18 21:08:39 +01:00
parent f47981f51e
commit 6989ba0174
1 changed files with 17 additions and 6 deletions
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23
Objects/unicodeobject.c
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@ -13106,6 +13106,13 @@ int
_PyUnicodeWriter_PrepareInternal(_PyUnicodeWriter *writer,
Py_ssize_t length, Py_UCS4 maxchar)
{
#ifdef MS_WINDOWS
/* On Windows, overallocate by 50% is the best factor */
# define OVERALLOCATE_FACTOR 2
#else
/* On Linux, overallocate by 25% is the best factor */
# define OVERALLOCATE_FACTOR 4
#endif
Py_ssize_t newlen;
PyObject *newbuffer;
@ -13121,9 +13128,10 @@ _PyUnicodeWriter_PrepareInternal(_PyUnicodeWriter *writer,
if (writer->buffer == NULL) {
assert(!writer->readonly);
if (writer->overallocate && newlen <= (PY_SSIZE_T_MAX - newlen / 4)) {
/* overallocate 25% to limit the number of resize */
newlen += newlen / 4;
if (writer->overallocate
&& newlen <= (PY_SSIZE_T_MAX - newlen / OVERALLOCATE_FACTOR)) {
/* overallocate to limit the number of realloc() */
newlen += newlen / OVERALLOCATE_FACTOR;
}
if (newlen < writer->min_length)
newlen = writer->min_length;
@ -13133,9 +13141,10 @@ _PyUnicodeWriter_PrepareInternal(_PyUnicodeWriter *writer,
return -1;
}
else if (newlen > writer->size) {
if (writer->overallocate && newlen <= (PY_SSIZE_T_MAX - newlen / 4)) {
/* overallocate 25% to limit the number of resize */
newlen += newlen / 4;
if (writer->overallocate
&& newlen <= (PY_SSIZE_T_MAX - newlen / OVERALLOCATE_FACTOR)) {
/* overallocate to limit the number of realloc() */
newlen += newlen / OVERALLOCATE_FACTOR;
}
if (newlen < writer->min_length)
newlen = writer->min_length;
@ -13169,6 +13178,8 @@ _PyUnicodeWriter_PrepareInternal(_PyUnicodeWriter *writer,
}
_PyUnicodeWriter_Update(writer);
return 0;
#undef OVERALLOCATE_FACTOR
}
Py_LOCAL_INLINE(int)