[Python-Dev] Tunable parameters in dictobject.c (was dictnotes.txt out of date?) (original) (raw)

Raymond Hettinger raymond.hettinger at gmail.com
Thu Jun 14 16:01:08 CEST 2012

On Jun 14, 2012, at 4:32 AM, Kristján Valur Jónsson wrote:

I would like to two or more compile time settings to choose from: Memory optimal, speed optimal, (and mix).

A compile time option would be nice.

The default should be what we've had though. The new settings cause a lot more collisions and resizes. The resizes themselves have more collisions than before (there are few collisions when resizing into a quadrupled dict than into a doubled dict).

Dicts get their efficiency from sparseness. Reducing the mindict size from 8 to 4 causes substantially more collisions in small dicts and gets closer to a linear search of a small tuple.

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