length of module name affecting performance??

Daniel Gorín dgorin at dc.uba.ar
Mon Dec 15 16:10:29 EST 2008


While trying to see if I could make some code run faster I stumbled  
upon something that looks weird to me: 2x-3x performance loss when a  
module is renamed to a longer name!

Here's what I see with the attached examples:

#diff long-modname-ver.hs short-modname-ver.hs
< import VeryLongModuleName
 > import ShortM

#diff VeryLongModuleName.hs ShortM.hs
< module VeryLongModuleName
 > module ShortM

#ghc --make -O2 -Wall long-modname-ver.hs

#ghc --make -O2 -Wall short-modname-ver.hs

#time -p ./long-modname-ver > /dev/null
real 55.90
user 55.17
sys 0.51

#time -p ./short-modname-ver > /dev/null
real 22.23
user 21.97
sys 0.10

I'm using GHC 6.10.1 on OS X. Any ideas on what may be going on?


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