Message310570
I agree that an heuristic is needed to decide when a dict should be compacted.
> * When (dict size < dk_size/8), call insertion_resize()
In bpo-31179, I suggested to Yury to use 2/3 ratio... to avoid integer overflow :-) He first used 80%, but I dislike using the FPU in the dictobject.c. I'm not sure of the cost of switching from integers to floats, and more generally I hate rounding issues, so I prefer to use regular integers ;-)
+ (3) if 'mp' is non-compact ('del' operation does not resize dicts),
+ do fast-copy only if it has at most 1/3 non-used keys.
+
+ The last condition (3) is important to guard against a pathalogical
+ case when a large dict is almost emptied with multiple del/pop
+ operations and copied after that. In cases like this, we defer to
+ PyDict_Merge, which produces a compacted copy.
By the way, if dict automatically compacts itself automatically, do we still need Yury's test "is the dict compact"? |
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Date |
User |
Action |
Args |
2018-01-24 09:29:40 | vstinner | set | recipients:
+ vstinner, methane, serhiy.storchaka, yselivanov |
2018-01-24 09:29:40 | vstinner | set | messageid: <1516786180.82.0.467229070634.issue32623@psf.upfronthosting.co.za> |
2018-01-24 09:29:40 | vstinner | link | issue32623 messages |
2018-01-24 09:29:40 | vstinner | create | |
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