2010/4/7 Steven D'Aprano <st...@pearwood.info> > On Tue, 6 Apr 2010 04:25:08 pm Cesare Di Mauro wrote: > > > It will certainly. There's MUCH that can be optimized to let CPython > > squeeze more performance from static analysis (even a gross one) on > > locals. > [...] > > They are just "dummy" examples, but can make it clear how far > > optimizations can go with static analysis on locals. Python is a > > language that make it possible to use such analysis at compile time, > > and I think it is a very good thing. > > I'm not opposed to the idea of optimisations in general (far from it!) > but in case anyone is thinking about doing any work in this area, > please be careful about floating point optimisations. E.g. given a float > x, you can't assume that x*0 == 0. Nor can you assume that 0-x is the > same as -x. (The second is *almost* always correct, except for one > float value.) > > See, for example, the various writings by Professor Kahan: > > http://www.drdobbs.com/184410314 > http://www.cs.berkeley.edu/~wkahan/ > > Most of the issues discussed apply to languages that deal with floats at > a lower level than Python does, but still, simple minded optimizations > will break corner cases no matter what language you use. > > -- > Steven D'Aprano
Thanks for the useful links. I never applied such kind of optimizations, and I think I'll never to do it anyway. :) Cesare
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