On Sun 18 Jun 06, 8:13 PM, Micah J. Cowan <[EMAIL PROTECTED]> said: > On Sun, Jun 18, 2006 at 08:26:21PM -0400, Peter Jay Salzman wrote: > > On Sun 18 Jun 06, 12:06 AM, Norm Matloff <[EMAIL PROTECTED]> said: > > > Pete Salzman asked about optimizing a loop in terms of execution speed, > > > by having the loop index go from high value to low instead of vice > > > versa. Some discussion ensued in terms of what machine instructions a > > > compiler could take advantage of in this manner. > > > > > > One point that you might consider, Pete, is that these considerations > > > are kind of nickel-and-dime in comparison to things like memory > > > hierarchy issue. There is much better payoff potential in writing code > > > in such a way as to minimize cache misses, which cause major time > > > penalties, and page faults, which cause catastrophic time penalties. > > > > Yeah, I know. My company hired me for algorithmic optimizations --- my > > knowledge of devising a set of algorithms to accomplish a given task (e.g., > > solving dense matrices, choosing a particular Monte Carlo for a given > > problem). > > > > I guess my attitude towards this was more along the lines of "while I'm in > > the neighborhood, why don't I stop by and say hello". It certainly wouldn't > > be prudent to re-implement code to use nickel and dime optimization, but > > while thoughts in my neurons travel down my CNS and translate into my > > fingers tapping on keys, I might as well tap on keys in such a way that the > > nickel and dime optimizations appear on vim's terminal. The price of > > admission is free, so I might as well. > > > > OK. I took that nutty metaphor as far as it can go. Hope it made sense. > > > > > There is even a book on this, I believe in the Intel Press series. > > > > Definitely sounds like a book I should pick up. I'll Google for it! > > Given your explanation above, you might also find Hacker's Delight > to be enjoyable reading (if you haven't read it already). > > ...just promise me you'll document the hell out of pretty much anything > you /use/ out of there... :-) You know... a long time ago I read a /. book review of this book and it's been in the back of my head for a long time. I never had the money to purchase it (I think it's still on my nerdbooks.com wishlist). You just reminded me of it. Yeah, that's a book I can afford now; I think I'll take the plunge.
I set up a wiki on www.dirac.org/programming to document everything I learn about programming, numerics, and numerical algorithms. Slowly but surely, a lot of my saved vox-tech messages (like this one) are getting documented there. I also plan on documenting things I learn from books like Hacker's Delight. Thanks for reminding me of this book! Pete _______________________________________________ vox-tech mailing list vox-tech@lists.lugod.org http://lists.lugod.org/mailman/listinfo/vox-tech