[clean-list] slown down by time annotation

[Valéry Croizier]

Flam returns an unboxed array,

  flam :: *{#Int} -> *{#Int}

so the compiler knows that t

  t = flam {{x+1 \\ x <- [1..n]} & [n-1] = 1}

is unboxed, and the type declaration

  t :: *{#Int}

is only a confirmation of what the compiler already knows. But the compiler is confused and calls the reverslice function 3 times instead of 1. Maybe it is a bug.


erik.zuurbier at tiscali.nl a écrit :

>Valery,
>
>If you don't have the type annotation, the array is a sequence 
>of pointers to other fields in the heap that contain the individual 
>integers.
>
>If you DO have the type annotation, the arrya is a sequence 
>of the actual integers themselves. That is usually a lot faster and it 
>saves space. But there are cases where they cannot be used. That has to 
>do with laziness.
>
>Regards Erik Zuurbier
>
>----Oorspronkelijk 
>bericht----
>Van: valery at freesurf.fr
>Datum : 14/07/2005 14:51
>Aan: 
><clean-list at science.ru.nl>
>Onderw: [clean-list] slown down by time 
>annotation
>
>Hello Clean users.
>
>I have written a few programs to taste 
>the language, and the one below 
>is about arrays.
>What puzzles me is 
>the type annotation commented out in 'showflam', 
>which makes the 
>program 3 times slower.
>
>Can anybody explain me what's happening ?
>
>Valery.
>
>swap :: *{#Int} !Int !Int -> *{#Int}
>swap t i j
>  #! ti = t.
>[i]
>  #! tj = t.[j]
>  = {t & [i] = tj, [j] = ti}
>
>reverslice :: !Int !
>Int *{#Int} -> *{#Int}
>reverslice i j t
>  | i < j     = reverslice (inc 
>i) (dec j) (swap t i j)
>  | otherwise = t
>
>flam :: *{#Int} -> *{#Int}
>flam t
>  #! end = t.[0]
>  | end == 1 = t
>  | otherwise  = flam 
>(reverslice 0 (end - 1) t)
>
>showflam :: !Int -> [Int]
>showflam n
>  #! 
>t1 = t.[1]
>  #! t2 = t.[n / 2]
>  #! t3 = t.[n - 1]
>  = [ t1, t2, t3 ] 
>where
>//  t :: *{#Int} // slows down 3X
>  t = flam {{x+1 \\ x <- [1..
>n]} & [n-1] = 1}
>
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