[Arrays] Random Access Times ?

[Derek Elkins]

On Sat, 3 May 2003 10:37:32 -0700 (PDT)
Ron de Bruijn <rondebruijn@yahoo.com> wrote:

> Hi there,
> 
> I tested below program with for x filled in 1 and
> 50000. And I saw that when I used 50000 it took more
> than ten times more time than when I used 1, to
> complete the expression. So much for randow access
> memory(RAM). 
> 
> Isn't there somekind of other array that really works
> with random access? 
> 
> module Test where
> 
> import IOExts
> 
> data Lesson = Lesson String Int Int String String
> 	deriving Show
> 
> main = do
> 	testing <- newIOArray (0,60000) (Lesson "Hallo" 0 0
> "" "")
> 	sequence(map(writeIOArray testing x) (test))
> 	a<-readIOArray testing 0
> 	putStr (decompose a)
> 
> test::[Lesson]
> test=(replicate 100000 (Lesson "" 1 2 "" ""))
> 
> decompose (Lesson s1 _ _ _ _) = s1

Haskell is a lazy language.  It may be that Hugs lazily fills the array,
in which case writing to index 1 will only force it to write out 3
elements (index 0,1 and what you are writing).  Writing to 50000 would
force it to write out 0-50000 first.  Try touching each element of the
array, then timing lookup.