🚀 go-pugleaf

In article <1993Jan07.200247.37029@dcc.uchile.cl> maurro@inf.utfsm.cl (Mauricio Gomez Calderon) writes:
>   But what about the best times? 6 sec in Helios and 10 sec in D7205 for the
>   almost 'same' application... Furthermore, the occam process is the only
>   process in the transputer...
>
>   Why this difference?         Thanks in Advance...

I can perhaps offer one suggestion; you are not comparing similar programs.
 
I know it sounds trivial, but in C you are using:

>   void cycle(int iterations) {
>
>        int i;
>       for(i=0; i<iterations; i++) {
>           /* nothing! */
>           }
>
>   }

whereas in occam you have:
      
>   VAL INT iterations IS 10000000:
>   SEQ
>     clock ? time1
>     i := 0
>     WHILE ( i < iterations )
>       SEQ
>         -- nothing!
>        i := i + 1
>     clock ? time2
       
The C version holds `iterations' as a variable, whereas the occam program
has a constant. Large constants are (relatively) expensive on a transputer;
it is faster to load a local variable than to generate the
constant '10000000'.
       
Try changing the occam to something equivalent to the C:

  PROC cycle(VAL INT iterations)
    INT i :
    SEQ
      i := 0
      WHILE i < iterations
        i := i + 1
  :
  
You will find that this is the entire reason for the change.

The D4205A compiler produces this for the version with the constant
value for `iterations':

       0: 20 20 20                pfix    0
       3: 60 BF                   ajw     -1
       5: 40                      ldc     0
       6: D0                      stl     0
       7: 29 28 29 26 28 40       ldc     10000000
      13: 70                      ldl     0
      14: F9                      gt
      15: A5                      cj      5
      16: 70                      ldl     0
      17: 81                      adc     1
      18: D0                      stl     0
      19: 60 02                   j       -14
      21: B1                      ajw     1
      22: 22 F0                   ret

and this for the version where it is a formal parameter:

       0: 60 BF                   ajw     -1
       2: 40                      ldc     0
       3: D0                      stl     0
       4: 72                      ldl     2
       5: 70                      ldl     0
       6: F9                      gt
       7: A5                      cj      5
       8: 70                      ldl     0
       9: 81                      adc     1
      10: D0                      stl     0
      11: 60 07                   j       -9
      13: B1                      ajw     1
      14: 22 F0                   ret

The same problem would occur in C if you used the constant in the for loop.

---
Conor O'Neill, Software Group, INMOS Ltd., UK.
UK: conor@inmos.co.uk		US: conor@inmos.com
"It's state-of-the-art" "But it doesn't work!" "That is the state-of-the-art".