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Sorry, but this is not true at all

Sorry, but this is not true at all

Posted May 21, 2010 15:42 UTC (Fri) by vonbrand (guest, #4458)
In reply to: Sorry, but this is not true at all by khim
Parent article: PyPy: the other new compiler project

The delightful "Writing Efficient Programs" by Jon Bentley (sadly long out of print, but his "Programming Pearls" contains the gist of it) tells what to do to make programs go faster/use less memory: First you have to measure where the performance drains are, that turns out not to be at all evident (programmers are notoriously bad at guessing at them!). Look at the architecture of the program, check for more efficient algorithms. Then go look at the "small picture": Typical programs spend 95% of their time in 5% of their code. If you make that 5% go twice as fast, your program goes almost twice as fast; futzing around with the rest gives almost no improvement. Only if rewriting in your high level language hits the wall, consider rewriting in a lower level language. Plus never forget that hacking the program for efficiency has a cost in maintenability, and only under rare circumstances is the added programmer time of extreme measures worth the savings in computer time (and with Moore's law it is getting ever harder).


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