[issue24221] Clean-up and optimization for heapq siftup() and siftdown()
Roundup Robot added the comment: New changeset 490720fc1525 by Raymond Hettinger in branch 'default': Issue #24221: Small optimizations for heapq. https://hg.python.org/cpython/rev/490720fc1525 -- nosy: +python-dev ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue24221 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue24221] Clean-up and optimization for heapq siftup() and siftdown()
Changes by Raymond Hettinger raymond.hettin...@gmail.com: -- resolution: - fixed status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue24221 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue24221] Clean-up and optimization for heapq siftup() and siftdown()
Stefan Behnel added the comment: There are calls to PyObject_RichCompareBool() in the loops, which means that user code might get executed. What if that's evil code that modifies the heap list? Couldn't that lead to list resizing and thus invalidation of the list item pointer? -- nosy: +scoder ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue24221 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue24221] Clean-up and optimization for heapq siftup() and siftdown()
Serhiy Storchaka added the comment: The list item pointer is updated just after calling PyObject_RichCompareBool(). The code LGTM. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue24221 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue24221] Clean-up and optimization for heapq siftup() and siftdown()
Stefan Behnel added the comment: Ah, sorry, yes. I somehow misread the arguments being passed *into* richcompare as subsequent array access. LGTM too. Sorry for the noise. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue24221 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue24221] Clean-up and optimization for heapq siftup() and siftdown()
Serhiy Storchaka added the comment: Perhaps the code will look simpler if introduce the macro _PyList_SWAP_ITEMS(list, i, j). -- nosy: +serhiy.storchaka ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue24221 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue24221] Clean-up and optimization for heapq siftup() and siftdown()
New submission from Raymond Hettinger: The siftup() and siftdown() routines rearrange pointers in a list. The generated code repeats the list object to ob_item lookup for each access. This patch does that lookup only once per iteration. It cleans up the code by replacing the PyList_GET_ITEM and PyList_SET_ITEM macros with normal array access (the usual way of presenting the algorithm). This gives about a 5% speed-up using CLANG (timing heapify(data[:]) for n=1000 goes from .3441 per iteration to .3299). However on GCC-4.9, the same patch gives a 2% slow-down (disassembly shows that this patch triggers a register spill and load in the inner loop which is a bummer). Since it speeds-up some builds and slows down others, I'm uncertain what to do with this one. I like the way the code reads with array accesses but was aiming for a consistent win. Am posting the patch here to collect thoughts on the subject and to not lose the work. -- components: Extension Modules files: heapitems5.diff keywords: patch messages: 243444 nosy: rhettinger priority: normal severity: normal status: open title: Clean-up and optimization for heapq siftup() and siftdown() type: performance versions: Python 3.5 Added file: http://bugs.python.org/file39413/heapitems5.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue24221 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue24221] Clean-up and optimization for heapq siftup() and siftdown()
Changes by Raymond Hettinger raymond.hettin...@gmail.com: Added file: http://bugs.python.org/file39414/time_heapify.py ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue24221 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue24221] Clean-up and optimization for heapq siftup() and siftdown()
Changes by Raymond Hettinger raymond.hettin...@gmail.com: -- priority: normal - low ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue24221 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
