[Python-Dev] speeding up PyObject_GetItem (original) (raw)

Raymond Hettinger python at rcn.com
Tue Mar 24 10:46:31 CET 2009

Agreed, and more importantly, I have yet to be convinced that those NULL checks introduce a measurable slowdown. Daniel, have you tried measuring the performance difference with only the NULL checks removed?

I think it highly unlikely that there is a performance difference. These tend to branch the same way every time, so the processor's branch prediction will tend to reduce the check time to near zero.

I think it would be fine to add a special case for lists (*) and dicts in PyObjectGetItem(), provided it does make a significant difference in performance for these two types.

-1

The API confusion and clutter isn't worth the micro-optimization. Also, the checks probably do have some value in early detection of programming errors; it would be ashamed to lose them in non-debug builds. When we get bug reports that are due to problems with third-party extensions, it will be harder to know whether the issue is with the extension or with us.

Raymond

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