On Wed, Dec 31, 2014 at 3:12 PM, Serhiy Storchaka <storch...@gmail.com> wrote: > On 10.12.12 03:44, Raymond Hettinger wrote: >> >> The current memory layout for dictionaries is >> unnecessarily inefficient. It has a sparse table of >> 24-byte entries containing the hash value, key pointer, >> and value pointer. >> >> Instead, the 24-byte entries should be stored in a >> dense table referenced by a sparse table of indices. > > > FYI PHP 7 will use this technique [1]. In conjunction with other > optimizations this will decrease memory consumption of PHP hashtables up to > 4 times.
"up to 4 times" is a bit of a stretch, given that most of their savings come from: * saving on the keeping of ordering * other optimizations in zval None of it applies to python PHP does not implement differing sizes of ints in key dict, which makes memory saving php-only (if we did the same thing as PHP, we would save more or less nothing, depending on how greedy you are with the list overallocation) We implemented the same strategy in PyPy as of last year, testing it to become a default "dict" and "OrderedDict" for PyPy in the next release. Cheers, fijal PS. I wonder who came up with the idea first, PHP or rhettinger and who implemented it first (I'm pretty sure it was used in hippy before it was used in Zend PHP) _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
