INADA Naoki added the comment:
Only patch which affects to hot loop is:
--- a/Objects/dictobject.c Tue Nov 15 21:21:35 2016 -0500
+++ b/Objects/dictobject.c Wed Nov 16 11:40:51 2016 +0000
@@ -1550,11 +1550,18 @@ PyDict_MergeFromSeq2(PyObject *d, PyObje
/* Update/merge with this (key, value) pair. */
key = PySequence_Fast_GET_ITEM(fast, 0);
value = PySequence_Fast_GET_ITEM(fast, 1);
+ Py_INCREF(key);
+ Py_INCREF(value);
if (override || PyDict_GetItem(d, key) == NULL) {
int status = PyDict_SetItem(d, key, value);
- if (status < 0)
+ if (status < 0) {
+ Py_DECREF(key);
+ Py_DECREF(value);
goto Fail;
+ }
}
+ Py_DECREF(key);
+ Py_DECREF(value);
Py_DECREF(fast);
Py_DECREF(item);
}
Microbenchmark for it:
$ ~/local/py35/bin/master -m perf timeit --rigorous -t --python
~/local/py35/bin/patched --compare-to ~/local/py35/bin/master -s 'L = [(i,i)
for i in range(10000)]' -- 'dict.fromkeys(L)'
Benchmark master
================
.........................................Total duration: 21.2 sec
Start date: 2016-11-17 12:21:39
End date: 2016-11-17 12:22:13
Raw sample minimum: 109 ms
Raw sample maximum: 144 ms
Number of runs: 41
Total number of samples: 120
Number of samples per run: 3
Number of warmups per run: 1
Loop iterations per sample: 32
Minimum: 3.41 ms (-13%)
Median +- std dev: 3.92 ms +- 0.19 ms
Mean +- std dev: 3.92 ms +- 0.19 ms
Maximum: 4.50 ms (+15%)
Median +- std dev: 3.92 ms +- 0.19 ms
Benchmark patched
=================
.........................................Total duration: 21.3 sec
Start date: 2016-11-17 12:22:13
End date: 2016-11-17 12:22:47
Raw sample minimum: 108 ms
Raw sample maximum: 152 ms
Number of runs: 41
Total number of samples: 120
Number of samples per run: 3
Number of warmups per run: 1
Loop iterations per sample: 32
Minimum: 3.39 ms (-14%)
Median +- std dev: 3.92 ms +- 0.23 ms
Mean +- std dev: 3.95 ms +- 0.23 ms
Maximum: 4.74 ms (+21%)
Median +- std dev: 3.92 ms +- 0.23 ms
Compare
=======
Median +- std dev: [master] 3.92 ms +- 0.19 ms -> [patched] 3.92 ms +- 0.23 ms:
1.00x slower
Not significant!
----------
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue27945>
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