On Thursday 18 November 2010 11:24:24, Daniel Seidel wrote:
Hi,
I was doing some heap profiles and ran into the following issue.
Consider the program fib.hs:
module Main where
fib i | i == 0 || i == 1 = 1
| i > 1 = fib (i-1) + fib (i-2) | otherwise = 0
testWhere = {-# SCC "Where" #-} res where res = fib 35
testLet = {-# SCC "Let" #-} let res = fib 35 in res
Can anyone please tell me, if this is the expected behavior?
I think so. testWhere is equivalent to testLet2 = let res = fib35 in {-# SCC "Where" #-} res so the cost centre covers only the result, not the computation. To get the computation into the cost centre, use testWhere = res where res = {-# SCC "Where" #-} fib 35 which corresponds to let res = {-# SCC "Whatever" #-} fib 35 in res
I'm not very experienced in benchmarking and was a bit irritated by that difference.
Cheers, Daniel.
Ditto ;)