Re: OOS approach revisited

On Thu, 26 Jun 2025 17:27:48 +0000, LIT wrote:

The saving come from rolling  @ @ + ! into a single very specialized
function.  But what about the loading of X Y and retrieving of Z which
are unavoidable in practice?  Should that not be included in the test?

>
Let's find out then:
>
1 VARIABLE X
2 VARIABLE Y
3 VARIABLE Z
>
: TEST1 1000 0 DO 10000 0 DO
    I DUP X ! Y ! X @ Y @ + Z ! Z @ DROP
  LOOP LOOP ;
: TEST2 1000 0 DO 10000 0 DO
    I DUP X ! Y ! X Y Z +> Z @ DROP
  LOOP LOOP ;
TICKS TEST1 TICKS 2SWAP DMINUS D+ D. 252 ok
TICKS TEST2 TICKS 2SWAP DMINUS D+ D. 202 ok
>
: TEST1 1000 0 DO 10000 0 DO
    I DUP X ! Y ! 1 X +! 1 Y +! X @ Y @ + Z ! Z @ DROP
  LOOP LOOP ;
: TEST2 1000 0 DO 10000 0 DO
    I DUP X ! Y ! X ++ Y ++  X Y Z +> Z @ DROP
  LOOP LOOP ;
TICKS TEST1 TICKS 2SWAP DMINUS D+ D. 346 ok
TICKS TEST2 TICKS 2SWAP DMINUS D+ D. 258 ok
>
The difference is smaller - still it's significant.
>
>
Another test - using the "drawing a box" example
from "Thinking Forth" (and "simulated" LINE word):
>
0 VARIABLE TOP
0 VARIABLE LEFT
0 VARIABLE BOTTOM
0 VARIABLE RIGHT
: LINE 2DROP 2DROP ;
>
: BOX1 ( x1 y1 x2 y2) BOTTOM ! RIGHT ! TOP ! LEFT !
 LEFT  @ TOP    @ RIGHT @ TOP    @ LINE
 RIGHT @ TOP    @ RIGHT @ BOTTOM @ LINE
 RIGHT @ BOTTOM @ LEFT  @ BOTTOM @ LINE
 LEFT  @ BOTTOM @ LEFT  @ TOP    @ LINE ;
>
: BOX2 ( x1 y1 x2 y2) BOTTOM ! RIGHT ! TOP ! LEFT !
 LEFT  TOP    RIGHT TOP    LINE
 RIGHT TOP    RIGHT BOTTOM LINE
 RIGHT BOTTOM LEFT  BOTTOM LINE
 LEFT  BOTTOM LEFT  TOP    LINE ;
>
: TEST1 1000 0 DO 10000 0 DO  I DUP 2DUP BOX1  LOOP LOOP ;
: TEST2 1000 0 DO 10000 0 DO  I DUP 2DUP BOX2  LOOP LOOP ;
>
TICKS TEST1 TICKS 2SWAP DMINUS D+ D. 890 ok
TICKS TEST2 TICKS 2SWAP DMINUS D+ D. 653 ok
>
>
The difference is even more significant in case
of multiplication:
>
1 VARIABLE X
2 VARIABLE Y
3 VARIABLE Z
>
: TEST1 1000 0 DO 10000 0 DO
    I DUP X ! Y ! X @ Y @ * Z ! Z @ DROP
  LOOP LOOP ;
: TEST2 1000 0 DO 10000 0 DO
    I DUP X ! Y ! X Y Z *> Z @ DROP
  LOOP LOOP ;
TICKS TEST1 TICKS 2SWAP DMINUS D+ D. 658 ok
TICKS TEST2 TICKS 2SWAP DMINUS D+ D. 200 ok
>
But this time better implementation has also
its impact; fig-Forth's '*' is inefficient,
and I coded '*>' of course directly in ML,
simply using IMUL.
>

With so many DO..LOOPs involved, be careful not to
measure more looping time than the multiplications.
IIRC DO..LOOPs had been a hack for computers in the 60s.
A rather ugly hack, born out of necessity, slow and
often cumbersome to use. That it still persists in Forth
half a century later speaks for Forth's progressiveness.
--