#1621: GHCi wrong execution time report
---------------------+------------------------------------------------------
Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: GHCi | Version: 6.6.1
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Architecture: x86_64 (amd64)
Os: Windows |
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Old description:
> Hello,
>
> using latest GHC 6.6.1 binary package for windows, I've received
> strange information about execution time for the module below.
>
> My machine: OS WinXP Pro SP2, Intel Core 2, 2GB RAM.
>
> How to reproduce error:
>
> :set +s
> :set -02
> :cd <path to the file in the attachment>
> :l Primes
>
> Then running
> take 10000 primes1
> take 10000 primes2
> take 10000 primes3
> take 10000 primes1'
> take 10000 primes2'
> take 10000 primes3'
>
> Results seem to be correct, but the execution time reported no. First
> column is the GHCi report, the second column is th stop-watch data (just
> to correlate). No other task, except core windows, was running at the
> moment.
>
> GHCi Stop-watch
> 236.03 672.2
> 63.52 63.9
> 63.01 64.0
> 1098.75 671.0
> -365.07 65.2 // it's not a typo, really minus three hundred and
> sixty five
> 63.59 63.6
>
> Best regards,
>
> Dusan
>
> ---------
> module Primes (
> primes1
> ,primes2
> ,primes3
> ,primes2'
> ,primes3'
> ) where
>
> candidates = map (\x -> (True,x)) [2..]
> candidates' = [2..]
>
> skipmap f toSkip list = domap toSkip list
> where
> domap n (x:xs)
> | n > 1 = x : domap (n-1) xs
> | True = f x : domap toSkip xs
> domap _ [] = []
>
> primes1 = sieve candidates
> where
> sieve (pp@(isp,p):xs)
> | isp = p : (sieve $ skipmap (\(_,v) -> (False,v)) p xs)
> | True = sieve xs
>
> primes1' = sieve candidates'
> where
> sieve (p:xs)
> | p > 0 = p : (sieve $ skipmap (\n -> if n>0 then (-n) else n) p
> xs)
> | True = sieve xs
>
>
> sieve (p:xs) = p : sieve [y | y <- xs, y `mod` p /= 0]
> sieve' (p:xs) = p : sieve [y | y <- xs, y `mod` p > 0]
>
> primes2 = sieve [2..]
> primes3 = 2 : sieve [3,5..]
>
> primes2' = sieve' [2..]
> primes3' = 2 : sieve' [3,5..]
New description:
Hello,
using latest GHC 6.6.1 binary package for windows, I've received strange
information about execution time for the module below.
My machine: OS WinXP Pro SP2, Intel Core 2, 2GB RAM.
How to reproduce error:
{{{
:set +s
:set -02
:cd <path to the file in the attachment>
:l Primes
}}}
Then running
{{{
take 10000 primes1
take 10000 primes2
take 10000 primes3
take 10000 primes1'
take 10000 primes2'
take 10000 primes3'
}}}
Results seem to be correct, but the execution time reported no. First
column is the GHCi report, the second column is th stop-watch data (just
to correlate). No other task, except core windows, was running at the
moment.
{{{
GHCi Stop-watch
236.03 672.2
63.52 63.9
63.01 64.0
1098.75 671.0
-365.07 65.2 // it's not a typo, really minus three hundred and
sixty five
63.59 63.6
}}}
Best regards,
Dusan
---------
{{{
module Primes (
primes1
,primes2
,primes3
,primes2'
,primes3'
) where
candidates = map (\x -> (True,x)) [2..]
candidates' = [2..]
skipmap f toSkip list = domap toSkip list
where
domap n (x:xs)
| n > 1 = x : domap (n-1) xs
| True = f x : domap toSkip xs
domap _ [] = []
primes1 = sieve candidates
where
sieve (pp@(isp,p):xs)
| isp = p : (sieve $ skipmap (\(_,v) -> (False,v)) p xs)
| True = sieve xs
primes1' = sieve candidates'
where
sieve (p:xs)
| p > 0 = p : (sieve $ skipmap (\n -> if n>0 then (-n) else n) p
xs)
| True = sieve xs
sieve (p:xs) = p : sieve [y | y <- xs, y `mod` p /= 0]
sieve' (p:xs) = p : sieve [y | y <- xs, y `mod` p > 0]
primes2 = sieve [2..]
primes3 = 2 : sieve [3,5..]
primes2' = sieve' [2..]
primes3' = 2 : sieve' [3,5..]
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1621#comment:1>
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