A nice little speed-up for filter():

- Use PyObject_Call() instead of PyEval_CallObject(), saves several
  layers of calls and checks.

- Pre-allocate the argument tuple rather than calling Py_BuildValue()
  each time round the loop.

- For filter(None, seq), avoid an INCREF and a DECREF.

diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 83931d997ee3ca01f4d376507c80dd72d5387067..660abeb039b12aff43c43d375c98524b79883088 100644 (file)
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -122,7 +122,7 @@ Note that classes are callable, as are instances with a __call__() method.");
 static PyObject *
 builtin_filter(PyObject *self, PyObject *args)
 {
-       PyObject *func, *seq, *result, *it;
+       PyObject *func, *seq, *result, *it, *arg;
        int len;   /* guess for result list size */
        register int j;
 
@@ -151,6 +151,11 @@ builtin_filter(PyObject *self, PyObject *args)
        if (len < 0)
                len = 8;  /* arbitrary */
 
+       /* Pre-allocate argument list tuple. */
+       arg = PyTuple_New(1);
+       if (arg == NULL)
+               goto Fail_arg;
+
        /* Get a result list. */
        if (PyList_Check(seq) && seq->ob_refcnt == 1) {
                /* Eww - can modify the list in-place. */
@@ -166,7 +171,7 @@ builtin_filter(PyObject *self, PyObject *args)
        /* Build the result list. */
        j = 0;
        for (;;) {
-               PyObject *item, *good;
+               PyObject *item;
                int ok;
 
                item = PyIter_Next(it);
@@ -177,24 +182,20 @@ builtin_filter(PyObject *self, PyObject *args)
                }
 
                if (func == Py_None) {
-                       good = item;
-                       Py_INCREF(good);
+                       ok = PyObject_IsTrue(item);
                }
                else {
-                       PyObject *arg = Py_BuildValue("(O)", item);
-                       if (arg == NULL) {
-                               Py_DECREF(item);
-                               goto Fail_result_it;
-                       }
-                       good = PyEval_CallObject(func, arg);
-                       Py_DECREF(arg);
+                       PyObject *good;
+                       PyTuple_SET_ITEM(arg, 0, item);
+                       good = PyObject_Call(func, arg, NULL);
+                       PyTuple_SET_ITEM(arg, 0, NULL);
                        if (good == NULL) {
                                Py_DECREF(item);
                                goto Fail_result_it;
                        }
+                       ok = PyObject_IsTrue(good);
+                       Py_DECREF(good);
                }
-               ok = PyObject_IsTrue(good);
-               Py_DECREF(good);
                if (ok) {
                        if (j < len)
                                PyList_SET_ITEM(result, j, item);
@@ -216,12 +217,15 @@ builtin_filter(PyObject *self, PyObject *args)
                goto Fail_result_it;
 
        Py_DECREF(it);
+       Py_DECREF(arg);
        return result;
 
 Fail_result_it:
        Py_DECREF(result);
 Fail_it:
        Py_DECREF(it);
+Fail_arg:
+       Py_DECREF(arg);
        return NULL;
 }