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Re: Forth vs Java in calculating partial sum ;)

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Bernd Paysan <bernd.paysan@gmx.de> writes:
>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 ;

Disadvantage: fetches every cell twice, and you have a recurrence
through memory, which may be quite expensive, maybe not on current
Intel processors, but on older Intel ones, and probably on many other
machines.  So for performance I would write this as

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

(untested).  And the loop body is even one char shorter:-).

Here are the loop bodies on VFX:

Melzzzzz            Paysan              Ertl            
MOV EDX, [ESP]      MOV EDX, [ESP]      MOV EDX, [ESP]  
SHL EDX, 02         MOV ECX, [ESP]      ADD EBX, 0 [EDX]
ADD EDX, [EBP]      MOV EAX, 0 [EDX]    MOV EDX, [ESP]  
ADD EBX, 0 [EDX]    ADD [ECX+04], EAX   MOV 0 [EDX], EBX
MOV EDX, [ESP]      ADD [ESP], 04       ADD [ESP], 04   
SHL EDX, 02         ADD [ESP+04], 04    ADD [ESP+04], 04
ADD EDX, [EBP]      JNO 080BF3B0        JNO 080BF428    
MOV 0 [EDX], EBX
ADD [ESP], 01
ADD [ESP+04], 01
JNO 080BF338

Allocating I (and the conditioned loop bound) into a register might
pay off for this kind of code.

As for the benchmark: Sure, when you do a tiny benchmark that uses int
instead of Integer, and uses arrays instead of something from the Java
Collection classes, like ArrayList, then the Java JIT can shine.  And
to make sure of that, the original benchmark used a size (50*1000*1000
ints, i.e., 200MB) that far exceeds cache sizes, so any remaining
inefficiencies get swamped in the cache misses.

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
     New standard: http://www.forth200x.org/forth200x.html
   EuroForth 2013: http://www.euroforth.org/ef13/

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Forth vs Java in calculating partial sum ;) Melzzzzz <mel@zzzzz.com> - 2014-04-12 19:11 +0200
  Re: Forth vs Java in calculating partial sum ;) Paul Rubin <no.email@nospam.invalid> - 2014-04-12 10:15 -0700
    Re: Forth vs Java in calculating partial sum ;) Melzzzzz <mel@zzzzz.com> - 2014-04-14 22:15 +0200
      Re: Forth vs Java in calculating partial sum ;) stephenXXX@mpeforth.com (Stephen Pelc) - 2014-04-14 23:20 +0000
        Re: Forth vs Java in calculating partial sum ;) Melzzzzz <mel@zzzzz.invalid> - 2014-04-15 04:18 +0200
          Re: Forth vs Java in calculating partial sum ;) m.a.m.hendrix@tue.nl - 2014-04-15 00:32 -0700
            Re: Forth vs Java in calculating partial sum ;) stephenXXX@mpeforth.com (Stephen Pelc) - 2014-04-15 11:33 +0000
            Re: Forth vs Java in calculating partial sum ;) Melzzzzz <mel@zzzzz.com> - 2014-04-15 15:55 +0200
          Re: Forth vs Java in calculating partial sum ;) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-04-15 14:44 +0000
            Re: Forth vs Java in calculating partial sum ;) Paul Rubin <no.email@nospam.invalid> - 2014-04-15 09:00 -0700
              Re: Forth vs Java in calculating partial sum ;) Melzzzzz <mel@zzzzz.invalid> - 2014-04-15 19:38 +0200
            Re: Forth vs Java in calculating partial sum ;) mhx@iae.nl - 2014-04-15 11:41 -0700
            Re: Forth vs Java in calculating partial sum ;) Melzzzzz <mel@zzzzz.com> - 2014-04-16 07:10 +0200
            Re: Forth vs Java in calculating partial sum ;) Melzzzzz <mel@zzzzz.com> - 2014-04-16 07:24 +0200
              Re: Forth vs Java in calculating partial sum ;) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-04-16 10:24 +0000
  Re: Forth vs Java in calculating partial sum ;) mhx@iae.nl - 2014-04-12 13:01 -0700
    Re: Forth vs Java in calculating partial sum ;) mhx@iae.nl - 2014-04-12 13:06 -0700
    Re: Forth vs Java in calculating partial sum ;) Paul Rubin <no.email@nospam.invalid> - 2014-04-12 15:49 -0700
      Re: Forth vs Java in calculating partial sum ;) mhx@iae.nl - 2014-04-12 23:00 -0700
        Re: Forth vs Java in calculating partial sum ;) Paul Rubin <no.email@nospam.invalid> - 2014-04-13 00:14 -0700
          Re: Forth vs Java in calculating partial sum ;) mhx@iae.nl - 2014-04-13 02:03 -0700
        Re: Forth vs Java in calculating partial sum ;) Bernd Paysan <bernd.paysan@gmx.de> - 2014-04-13 14:52 +0200
    Re: Forth vs Java in calculating partial sum ;) "WJ" <w_a_x_man@yahoo.com> - 2014-12-12 23:45 +0000
  Re: Forth vs Java in calculating partial sum ;) mhx@iae.nl - 2014-04-12 13:33 -0700
    Re: Forth vs Java in calculating partial sum ;) Bernd Paysan <bernd.paysan@gmx.de> - 2014-04-12 22:50 +0200
      Re: Forth vs Java in calculating partial sum ;) Melzzzzz <mel@zzzzz.invalid> - 2014-04-13 03:30 +0200
      Re: Forth vs Java in calculating partial sum ;) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-04-13 13:43 +0000
  Re: Forth vs Java in calculating partial sum ;) Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-04-15 10:05 -0500
  Re: Forth vs Java in calculating partial sum ;) "WJ" <w_a_x_man@yahoo.com> - 2014-12-05 05:46 +0000
  Re: Forth vs Java in calculating partial sum ;) "WJ" <w_a_x_man@yahoo.com> - 2014-12-10 09:50 +0000
    Re: Forth vs Java in calculating partial sum ;) "WJ" <w_a_x_man@yahoo.com> - 2014-12-10 18:29 +0000

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