compiling large file hogs RAM and takes a long time.
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Date:   (:) 
From:  Thomas Fischbacher <tf@f...> 
Subject:  Re: [Camllist] Re: compiling large file hogs RAM and takes a long time. 
skaller wrote: > Perhaps you're right .. still, there's a big difference > between a 5 minute compile (enough time to make a coffee!) > and a 2 hour compile (enough time to have lunch!) The point I wanted to make here is: when it comes to the evaluation whether extra logarithmic factors in time complexity do matter or not, it is very important to also pay attention to the constants involved. For example, take a set of N magnetic needles distributed randomly over space. In order to find the magnetic field experienced by every single needle that is created by all the others, you can do a naive O(N^2) algorithm that just sums contributions. There is a more clever  and technically very sophisticated  technique that uses multipole expansions to get a good approximation (the "fast multipole method"), which can be computed in O(N log N), but the constants are such that the break even point is not reached before N=1000, and depending how well your code is written, may lie above N=5000. If such a situation arouse, I would, for example, not have any objections against trading an O(N log N) algorithm for an O(N log N log N) algorithm that is conceptually so much simpler that the constant factor is smaller by two orders of magnitude... > I usually illustrate this by asking if you'd be happy > to give up your 2 / 52 week annual holiday .. that's > under 4% of the year.. I'm sure you'd be horrified .. > 4% is a LOT! I am always amazed when I hear this, thinking that we Europeans typically get at least 5 weeks of holiday per year. :) Admittedly, according to the CIA world factbook, GDP per capita is about 1/4 higher in the US than in Germany (say), but I still prefer the more relaxed European model.  best regards, Thomas Fischbacher tf@functionality.de