[Haskell-cafe] how to make haskell faster than python at finding
primes?
Alex Jacobson
alex at alexjacobson.com
Mon Aug 6 04:15:46 EDT 2007
The challenge was the implement the modcount algorithm not to calculate
primes per se.
(see e.g. http://jjinux.blogspot.com/2005/11/io-comparison.html).
-Alex-
Donald Bruce Stewart wrote:
> alex:
>> This implementation of calculating 10000 primes (compiled with GHC -O2)
>> is 25% slower than the naive python implementation. Shouldn't it be
>> faster? Am I doing something obviously stupid?
>
> Why not just:
>
> primes = sieve [2..]
>
> sieve (p : xs) = p : sieve [x | x <- xs, x `mod` p > 0]
>
> main = print (take 1000 primes)
>
> That's super naive, and seems to be around 5x faster than the code you were
> trying. (So make sure you're doing the same thing as the python version)
>
> -- Don
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