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memoized: further fixes; hash objects whre possible

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This is further to commit 6d854fd4dc59936142fff811e575cd034a308c43

Due to the way certain objects are handled, getting the frist few bytes
of an object may not be enough (e.g. strings do not store their values
inline). To further mitigate the issue, hash the object where possible.
This commit is contained in:
Sergei Trofimov 2016-10-04 17:57:46 +01:00
parent f8440cf354
commit 09ec88e946
1 changed files with 17 additions and 13 deletions
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30
devlib/utils/misc.py
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@ -33,6 +33,7 @@ import ctypes
from operator import itemgetter
from itertools import groupby
from functools import partial
from collections import Hashable
import wrapt
@ -557,19 +558,22 @@ def __get_memo_id(obj):
ID string.
"""
obj_id = id(obj)
obj_pyobj = ctypes.cast(obj_id, ctypes.py_object)
# TODO: Note: there is still a possibility of a clash here. If Two
# different objects get assigned the same ID, an are large and are
# identical in the first thirty two bytes. This shouldn't be much of an
# issue in the current application of memoizing Target calls, as it's very
# unlikely that a target will get passed large params; but may cause
# problems in other applications, e.g. when memoizing results of operations
# on large arrays. I can't really think of a good way around that apart
# form, e.g., md5 hashing the entire raw object, which will have an
# undesirable impact on performance.
num_bytes = min(ctypes.sizeof(obj_pyobj), 32)
obj_bytes = ctypes.string_at(ctypes.addressof(obj_pyobj), num_bytes)
return '{}/{}'.format(obj_id, obj_bytes)
if isinstance(obj, Hashable):
return '{}/{}'.format(obj_id, hash(obj))
else:
obj_pyobj = ctypes.cast(obj_id, ctypes.py_object)
# TODO: Note: there is still a possibility of a clash here. If Two
# different objects get assigned the same ID, an are large and are
# identical in the first thirty two bytes. This shouldn't be much of an
# issue in the current application of memoizing Target calls, as it's very
# unlikely that a target will get passed large params; but may cause
# problems in other applications, e.g. when memoizing results of operations
# on large arrays. I can't really think of a good way around that apart
# form, e.g., md5 hashing the entire raw object, which will have an
# undesirable impact on performance.
num_bytes = min(ctypes.sizeof(obj_pyobj), 32)
obj_bytes = ctypes.string_at(ctypes.addressof(obj_pyobj), num_bytes)
return '{}/{}'.format(obj_id, obj_bytes)
@wrapt.decorator