Restore dicts' tp_compare slot, and change dict_richcompare to say it

doesn't know how to do LE, LT, GE, GT.  dict_richcompare can't do the
latter any faster than dict_compare can.  More importantly, for
cmp(dict1, dict2), Python *first* tries rich compares with EQ, LT, and
GT one at a time, even if the tp_compare slot is defined, and
dict_richcompare called dict_compare for the latter two because
it couldn't do them itself.  The result was a lot of wasted calls to
dict_compare.  Now dict_richcompare gives up at once the times Python
calls it with LT and GT from try_rich_to_3way_compare(), and dict_compare
is called only once (when Python gets around to trying the tp_compare
slot).
Continued mystery:  despite that this cut the number of calls to
dict_compare approximately in half in test_mutants.py, the latter still
runs amazingly slowly.  Running under the debugger doesn't show excessive
activity in the dict comparison code anymore, so I'm guessing the culprit
is somewhere else -- but where?  Perhaps in the element (key/value)
comparison code?  We clearly spend a lot of time figuring out how to
compare things.

diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index b6991538ec48a93da456415943393ec4328ea3e5..9b5b9f4c550991440a5d30b31d6b284cf5e43895 100644 (file)
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -1160,20 +1160,8 @@ dict_richcompare(PyObject *v, PyObject *w, int op)
                        return NULL;
                res = (cmp == (op == Py_EQ)) ? Py_True : Py_False;
        }
-       else {
-               cmp = dict_compare((dictobject *)v, (dictobject *)w);
-               if (cmp < 0 && PyErr_Occurred())
-                       return NULL;
-               switch (op) {
-                       case Py_LT: cmp = cmp <  0; break;
-                       case Py_LE: cmp = cmp <= 0; break;
-                       case Py_GT: cmp = cmp >  0; break;
-                       case Py_GE: cmp = cmp >= 0; break;
-                       default:
-                               assert(!"op unexpected");
-               }
-               res = cmp ? Py_True : Py_False;
-       }
+       else
+               res = Py_NotImplemented;
        Py_INCREF(res);
        return res;
  }
@@ -1541,7 +1529,7 @@ PyTypeObject PyDict_Type = {
        (printfunc)dict_print,                  /* tp_print */
        (getattrfunc)dict_getattr,              /* tp_getattr */
        0,                                      /* tp_setattr */
-       0,                                      /* tp_compare */
+       (cmpfunc)dict_compare,                  /* tp_compare */
        (reprfunc)dict_repr,                    /* tp_repr */
        0,                                      /* tp_as_number */
        &dict_as_sequence,                      /* tp_as_sequence */