New submission from Demur Rumed:
BUILD_MAP_UNPACK_WITH_CALL is _really_ slow, wasting much of its time asserting
that keys are non overlapping. This patch optimizes a fast path for distinct
dicts, especially useful for #27213 where BUILD_MAP_UNPACK_WITH_CALL is
generated for a single **kw rather than needing **kw1,**kw2 to hit this slow
opcode
This patch tracks size of dictionary, if size doesn't increase by same size as
the dict we updated sum with, then we scan to find where collision is. Further
optimization can be done by scanning size of dicts to preallocate dictionary
Microbenchmark:
from timeit import timeit
def f(**x):return x
timeit(lambda:f(**{'a':2},**{'b':2}))
Unpatched takes ~15s
Patched takes ~5s
----------
files: mapaca.patch
keywords: patch
messages: 268951
nosy: Demur Rumed
priority: normal
severity: normal
status: open
title: BUILD_MAP_UNPACK_WITH_CALL is slow
Added file: http://bugs.python.org/file43494/mapaca.patch
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<http://bugs.python.org/issue27358>
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