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From: Bernd Paysan <bernd.paysan@gmx.de>
Newsgroups: comp.lang.forth
Subject: Re: Forth vs Java in calculating partial sum ;)
Date: Sat, 12 Apr 2014 22:50:50 +0200
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mhx@iae.nl wrote:

> On Saturday, April 12, 2014 7:11:11 PM UTC+2, Melzzzzz wrote:
>> Seems that Java bits Forth in optimizing tight loops. Eg division by
>> constant optimization is performed automatically.
> 
> [..]
> 
> Paraphrased:
> 
> ANEW -cumul
> 
> #50000000 =: N
> N CELLS ALLOCATE ?ALLOCATE =: addr
> 
> : init_cumul ( -- ) addr  N 0 ?DO  I 3 / I +   SWAP !+   LOOP DROP ;
>           
> : cumul ( -- )
>         addr @+ ( [a] a -- )
>         N 1 ?DO
>                 OVER @ + DUP ( a [a]+x [a]+x -- )
>                 ROT !+ ( [a]+x a2 -- )        SWAP
>            LOOP 2DROP ;
> 
> : bench ( xt -- )
>         TIMER-RESET
>         EXECUTE
>         MS? S>F 1e-3 F* N S>F  F/  CR F.N1 ." s/op, "  .ELAPSED ;
> 
>   ' init_cumul bench
>   ' cumul      bench
> CR addr N 1- CELL[] @ .
>    addr FREE ?ALLOCATE
> 
> \ 3.68 ns/op, 0.186 seconds elapsed.
> \ 2.16 ns/op, 0.109 seconds elapsed.
> \ 1666666616666667  ok
> 
> I guess Java programmers are paid per LOC.

That's how I would write cumul (with the original stack effeckt, which 
Melzzzzz forgot to write):

: cumul ( addr -- addr )
    dup N 1- cells bounds ?do
	i @ i cell+ +!
    cell +loop ;

-- 
Bernd Paysan
"If you want it done right, you have to do it yourself"
http://bernd-paysan.de/