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SF bug #1085744: Performance issues with PySequence_Tuple()

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* Added missing error checks.
* Fixed O(n**2) growth pattern.  Modeled after lists to achieve linear
  amortized resizing.  Improves construction of "tuple(it)" when "it" is
  large and does not have a __len__ method.  Other cases are unaffected.
This commit is contained in:
Raymond Hettinger 2004-12-16 10:38:38 +00:00
parent 8a6a59c58b
commit 4d01259fb2
1 changed files with 14 additions and 4 deletions
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18
Objects/abstract.c
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@ -1427,10 +1427,20 @@ PySequence_Tuple(PyObject *v)
break; break;
} }
if (j >= n) { if (j >= n) {
if (n < 500) int oldn = n;
n += 10; /* The over-allocation strategy can grow a bit faster
else than for lists because unlike lists the
n += 100; over-allocation isn't permanent -- we reclaim
the excess before the end of this routine.
So, grow by ten and then add 25%.
*/
n += 10;
n += n >> 2;
if (n < oldn) {
/* Check for overflow */
PyErr_NoMemory();
goto Fail;
}
if (_PyTuple_Resize(&result, n) != 0) { if (_PyTuple_Resize(&result, n) != 0) {
Py_DECREF(item); Py_DECREF(item);
goto Fail; goto Fail;