On 4/2/06, Noam Raphael <[EMAIL PROTECTED]> wrote: > On 4/2/06, Guido van Rossum <[EMAIL PROTECTED]> wrote: > > > I tried the change, and it turned out that I had to change cPickle a > > > tiny bit: it uses a 2-tuple which is allocated when the module > > > initializes to lookup tuples in a dict. I changed it to properly use > > > PyTuple_New and Py_DECREF, and now the complete test suite passes. I > > > run test_cpickle before the change and after it, and it took the same > > > time (0.89 seconds on my computer). > > > > Not just cPickle. I believe enumerate() also reuses a tuple. > > Maybe it does, but I believe that it doesn't calculate the hash value > of it - otherwise, the test suite would probably have failed.
But someone else could. > > > What do you think? I see three possibilities: > > > 1. Nothing should be done, everything is as it should be. > > > 2. The cPickle module should be changed to not abuse the tuple, but > > > there's no reason to add an extra word to the tuple structure and > > > break binary backwards compatibility. > > > 3. Both should be changed. > > > > I'm -1 on the change. Tuples are pretty fundamental in Python and > > hashing them is relatively rare. I think the extra required space for > > all tuples isn't worth the potential savings for some cases. > > That's fine with me. But what about option 2? Perhaps cPickle (and > maybe enumerate) should properly discard their tuples, so that if > someone in the future decides that saving the hash value is a good > idea, he won't encounter strange bugs? At least in cPickle I didn't > notice any loss of speed because of the change, and it's quite > sensible, since there's a tuple-reuse mechanism anyway. No, these are carefully considered speed-ups. -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
