[Python-Dev] Comparison speed (original) (raw)

Tim Peters tim.one@home.com
Sun, 20 May 2001 06:13:14 -0400

[Guido]

I have always thought that eventually (but long before Py3K!) all objects would only support rich comparisons and the cmp and tpcompare slots would become completely obsolete.

If the time machine batteries can hold a full charge, you may want to go back and add Py_CMP as a seventh possible desired-operation argument to tbe rich comparison API. My experience with dict comparisons was that dict_richcompare couldn't compute Py_LT/LE/GT/GE any cheaper than by doing a full cmp, so I put the dict oldcmp back in order to avoid having dict richcmp (potentially) compute cmp 3 times to fake one cmp. But if dict richcmp knew a cmp outcome was desired, it could compute it with no extra work to speak of. Then there would be no reason at all to hold on to the dict tp_compare slot.

The list and tuple richcmps are also doing almost all the work needed to compute a 3-way cmp outcome.