Didn't think it was overly slow, just that I could do better :-). On Tuesday 13 February 2007 16:30, apfelmus@quantentunnel.de wrote:
Jefferson Heard wrote:
Argh, bitten by the scheme bug! Right -- NO tail recursion... So that leaves me with some rather non-intuitive strategies for achieving execution time efficiency. Anyone care to point me in the direction of a document on efficiency in Haskell?
Besides, proper tail recursion in Haskell needs strictness annotations, but the best way is to forget the two words "tail recursive" altogether :)
It always helps to do a rough calculation of how much time you have to expect it to run. Processing 1TB with a 1GHz processor and 16=2^4 machine instruction in the inner loop (must be quite short, the loop) takes
2^40 / (2^30 / 16) = 2^14 seconds ~ 4.5 hours
Of course, these 4.5 hours are quite sensitive to the 2^4 factor and might well be 3 or 9 hours. Assuming that you ran alex on a String, the reported 36 hours are entirely reasonable, in the sense of alex not being overly slow.
Regards, apfelmus
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