Raymond Hettinger schrieb: > If I'm understanding what was done for dictionaries, the hash table can grow > larger than the range of hash values. Accordingly, I would expect large > dictionaries to have an unacceptably large number of collisions. OTOH, we > haven't heard a single complaint, so perhaps my understanding is off.
I think this would happen, but users don't have enough memory to notice it. For a dictionary with more than 4GEntries, you need 72GiB memory (8 byte for each key, value, and cached-hash). So you are starting to see massive collisions only when you have that much memory - plus in that dictionary, you would also need space for keys and values. Very few people have machines with 128+GiB main memory, so no complaints yet. But you are right: extending the hash value to be a 64-bit quantity was "forgotten", mainly because it isn't a count of something - and being "count of something" was the primary criterion for the 2.5 changes. > The other area where I expected to hear wailing and gnashing of teeth is > users > compiling with third-party extensions that haven't been updated to a > Py_ssize_t > API and still use longs. I would have expected some instability due to the > size > mismatches in function signatures -- the difference would only show-up with > giant sized data structures -- the bigger they are, the harder they fall. > OTOH, > there have not been any compliants either -- I would have expected someone to > submit a patch to pyport.h that allowed a #define to force Py_ssize_t back to > a > long so that the poster could make a reliable build that included non-updated > third-party extensions. On most 64-bit systems, there is also an option to run 32-bit programs (atleast on AMD64, Sparc-64, and PPC64 there is). So people are more likely to do that when they run into problems, rather than recompiling the 64-bit Python. > In the absence of a bug report, it's hard to know whether there is a real > problem. Have all major third-party extensions adopted Py_ssize_t or is some > divine force helping unconverted extensions work with converted Python code? I know Matthias Klose has fixed all extension modules in the entire Debian source to compile without warnings on 64-bit machines. They may not work all yet, but yes, for all modules in Debian, it has been fixed. Not sure whether Matthias is a divine force, but working for Canonical comes fairly close :-) > Maybe the datasets just haven't gotten big enough yet. Primarily that. We still have a few years ahead to find all bugs before people would start complaining that Python is unstable on 64-bit systems. By the time people would actually see problems, hopefully they all have been resolved. Regards, Martin _______________________________________________ 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
