Thanks for the nice J version. It looks like I currently lack the time to
respond to your other points (or work out what the right hand side after ^:
exactly does), so I'll just post a quick timing you requested (and the steps
needed to replicate it) for the time being. Possibly more at some other time.
Oleg Kobchenko <[EMAIL PROTECTED]> writes:
> J504
> ham=: 3 : 'y.{.(2 3 5&([: /:[EMAIL PROTECTED]@, ] ,
> */))^:((+:y.)"_>:#)^:_] 1'
>
>
> 6!:2 'ham 8000'
> 0.234361
>
> ham1=: 3 : 'y{.(2 3 5&([: /:[EMAIL PROTECTED]@, ] , */))^:((+:y)>:#)^:_]
> 1x'
> 6!:2 'ham1 100000' NB. extended
> 62.5922
>
> How long will it take Haskell?
No time at all, since it won't need to do anything. I added the following line
main = print (take 1 $ drop hamming 100000)
and the compiled and run it with:
(ghc hamming.hs -O3 -o hamming; time ./hamming)
On my machine the floating point version and infinite precision integer
versions take pretty similar amount of time (0.04 for double float and 0.10s
for arbitrary precision integers; this contrasts with around 10s for ham and
84s for (the J504 version of) ham1 (there are some variations here, 84s is the
fastest I've observed, I've also had 260s).
Note: I do only have old versions of J and GHC, and I'm pretty ignorant about
GHC and Haskell (this is probably the first time I compiled something with it,
usually I rust run small snippets in GHCi) -- so I'm pretty sure one could get
(possibly significantly) better performance from both versions. If you really
want to know how fast you can get you'll have to ask on the haskell mailing
list or on comp.lang.functional (as I've briefly noted, understanding
performance issues of haskell code is non-trivial).
'as
To obtain the float version, replace e.g. 1 with 1.0
-- ->8- file hamming.hs ->8-
hamming = 1 : map (*2) hamming # (map (*3) hamming # map (*5) hamming)
where xxs@(x:xs) # yys@(y:ys)
| x==y = x : xs#ys
| x<=y = x : xs # yys
| x>y = y : xxs#ys
main = do print $ hamming !! 100000
-- ->8- file hamming.hs ->8-
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