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Re: Readable code and refactoring for optimization

Date 2011-12-09 17:46 -1000
From "Elizabeth D. Rather" <erather@forth.com>
Organization FORTH, Inc.
Newsgroups comp.lang.forth
Subject Re: Readable code and refactoring for optimization
References <4e9b11a0-cc0d-464e-a61c-a7867ffe2bfa@n1g2000yqk.googlegroups.com> <WvOdnUEBnP9pDEDTnZ2dnUVZ_sWdnZ2d@supernews.com> <7x8vmnzds3.fsf@ruckus.brouhaha.com> <jbqilt$4ld$1@dont-email.me>
Message-ID <gOSdnaP6RepkSH_TnZ2dnUVZ_qadnZ2d@supernews.com> (permalink)

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On 12/8/11 4:47 AM, Gerry Jackson wrote:
...
> 100 constant ndoors \ number of doors
> : array ( n -- )
> create cells allot
> does> ( i -- ad ) swap cells + ;
> 100 array doors \ allocate the array
>
> : init ( -- ) 0 doors ndoors cells erase ;
> : pass ( n -- ) \ toggle every nth door in the array.
> dup 1+ ndoors rot do 1 i doors +! dup +loop drop ;
> : run ( -- ) ndoors 0 do i pass loop ;
> : display ( -- ) ndoors 0 do i doors @ 1 and if i 1+ . then loop cr ;
>
> init run display \ bye
>
> Better or clearer - I don't know - opinions will differ.

Pretty good, but it could be faster (since we're proving that you don't 
have to be unreadable to be fast).

How's this:

: toggle ( caddr -- ) \ Toggle the byte at caddr
    dup c@ 1 xor swap c! ;  \ Many systems already have this.

100 constant ndoors
create doors ndoors allot

: init ( -- )   doors ndoors erase ;

: pass ( n -- )   \ toggle every nth door in the array.
    dup ndoors 1+ rot do
       doors i + toggle dup
    ( n ) +loop drop ;

: run ( -- )   ndoors 1+ 1 do  i pass  loop ;
: display ( -- )   ndoors 1+ 1 do  doors i + c@ if  i . then  loop cr ;


Notes:
1. I used bytes, instead of cells, since we're only using one bit.
2. I moved the 1+ outside the loop.
3. I tried it with a CREATE ... DOES> automatically indexing array, but 
it was slower.

This does 1000 iterations in 80 ms on my Macbook Pro with SwiftForth, 
compared with 82 ms for the "Factored" version at the OP's link (which 
is faster than the "Unfactored" example), and I think it's a lot clearer.

Cheers,
Elizabeth

-- 
==================================================
Elizabeth D. Rather   (US & Canada)   800-55-FORTH
FORTH Inc.                         +1 310.999.6784
5959 West Century Blvd. Suite 700
Los Angeles, CA 90045
http://www.forth.com

"Forth-based products and Services for real-time
applications since 1973."
==================================================

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Readable code and refactoring for optimization Wendell <wendellxe@yahoo.com> - 2011-12-05 18:14 -0800
  Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-05 17:54 -1000
    Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-05 17:58 -1000
      Re: Readable code and refactoring for optimization Hans Bezemer <thebeez@xs4all.nl> - 2011-12-06 08:49 +0100
    Re: Readable code and refactoring for optimization mhx@iae.nl (Marcel Hendrix) - 2011-12-06 07:26 +0200
      Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-05 22:02 -1000
      Re: Readable code and refactoring for optimization Bernd Paysan <bernd.paysan@gmx.de> - 2011-12-07 00:49 +0100
    Re: Readable code and refactoring for optimization Paul Rubin <no.email@nospam.invalid> - 2011-12-08 00:08 -0800
      Re: Readable code and refactoring for optimization anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-12-08 11:25 +0000
        Re: Readable code and refactoring for optimization Paul Rubin <no.email@nospam.invalid> - 2011-12-08 23:51 -0800
      Re: Readable code and refactoring for optimization Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2011-12-08 14:47 +0000
        Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2011-12-08 14:05 -0500
          Re: Readable code and refactoring for optimization Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2011-12-09 17:21 +0000
            Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2011-12-10 09:08 -0500
            Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-10 07:37 -1000
              Re: Readable code and refactoring for optimization Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2011-12-12 10:27 +0000
                Re: Readable code and refactoring for optimization Andrew Haley <andrew29@littlepinkcloud.invalid> - 2011-12-12 05:02 -0600
                Re: Readable code and refactoring for optimization Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2011-12-12 11:18 +0000
                Re: Readable code and refactoring for optimization Andrew Haley <andrew29@littlepinkcloud.invalid> - 2011-12-12 05:25 -0600
                Re: Readable code and refactoring for optimization Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2011-12-12 12:41 +0000
                Re: Readable code and refactoring for optimization Andrew Haley <andrew29@littlepinkcloud.invalid> - 2011-12-12 07:23 -0600
                Re: Readable code and refactoring for optimization Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2011-12-12 20:28 +0000
                Re: Readable code and refactoring for optimization Andrew Haley <andrew29@littlepinkcloud.invalid> - 2011-12-13 04:07 -0600
                Re: Readable code and refactoring for optimization Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2011-12-13 21:04 +0000
                Re: Readable code and refactoring for optimization Arnold Doray <thinksquared@gmail.com> - 2011-12-12 16:01 +0000
                Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2011-12-26 09:30 -0500
                Re: Readable code and refactoring for optimization Arnold Doray <invalid@invalid.com> - 2012-01-08 16:28 +0000
                Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2012-01-08 20:17 -0500
                Re: Readable code and refactoring for optimization Arnold Doray <invalid@invalid.com> - 2012-01-09 10:41 +0000
                Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2012-01-09 08:55 -0500
                Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2012-01-09 11:50 -0500
                Re: Readable code and refactoring for optimization Arnold Doray <invalid@invalid.com> - 2012-01-10 06:56 +0000
                Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2012-01-10 16:34 -0500
                Re: Readable code and refactoring for optimization Arnold Doray <invalid@invalid.com> - 2012-01-11 06:57 +0000
                Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2012-01-11 09:50 -0500
                Re: Readable code and refactoring for optimization Arnold Doray <invalid@invalid.com> - 2012-01-11 16:28 +0000
                Re: Readable code and refactoring for optimization Fritz Wuehler <fritz@spamexpire-201112.rodent.frell.theremailer.net> - 2011-12-12 22:57 +0100
                Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2011-12-26 09:30 -0500
        Re: Readable code and refactoring for optimization Paul Rubin <no.email@nospam.invalid> - 2011-12-08 23:53 -0800
        Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-09 17:46 -1000
          Re: Readable code and refactoring for optimization Josh Grams <josh@qualdan.com> - 2011-12-10 11:39 +0000
            Re: Readable code and refactoring for optimization Ian Osgood <iano@quirkster.com> - 2011-12-21 13:09 -0800
          Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2011-12-10 08:52 -0500
          Re: Readable code and refactoring for optimization Paul Rubin <no.email@nospam.invalid> - 2011-12-12 09:11 -0800
            Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-12 07:48 -1000
              Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2011-12-12 13:47 -0500
                Re: Readable code and refactoring for optimization Paul Rubin <no.email@nospam.invalid> - 2011-12-12 11:46 -0800
                Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2011-12-12 16:20 -0500
                Re: Readable code and refactoring for optimization BruceMcF <agila61@netscape.net> - 2011-12-12 13:48 -0800
                Re: Readable code and refactoring for optimization anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-12-13 10:31 +0000
              Re: Readable code and refactoring for optimization Paul Rubin <no.email@nospam.invalid> - 2011-12-12 11:42 -0800
                Re: Readable code and refactoring for optimization Mark Wills <markrobertwills@yahoo.co.uk> - 2011-12-12 13:35 -0800
                Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-12 11:49 -1000
                Re: Readable code and refactoring for optimization Paul Rubin <no.email@nospam.invalid> - 2011-12-12 23:50 -0800
                Re: Readable code and refactoring for optimization JennyB <jennybrien@googlemail.com> - 2011-12-13 03:04 -0800
  Re: Readable code and refactoring for optimization stephenXXX@mpeforth.com (Stephen Pelc) - 2011-12-06 11:04 +0000
    Re: Readable code and refactoring for optimization John Passaniti <john.passaniti@gmail.com> - 2011-12-06 05:52 -0800
  Re: Readable code and refactoring for optimization Arnold Doray <thinksquared@gmail.com> - 2011-12-06 13:52 +0000
    Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-06 08:22 -1000
      Re: Readable code and refactoring for optimization Arnold Doray <thinksquared@gmail.com> - 2011-12-07 08:55 +0000
  Re: Readable code and refactoring for optimization Doug Hoffman <glidedog@gmail.com> - 2011-12-11 07:29 -0500
    Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-11 08:59 -1000
      Re: Readable code and refactoring for optimization Mark Wills <forthfreak@gmail.com> - 2011-12-13 05:33 -0800
        Re: Readable code and refactoring for optimization Andrew Haley <andrew29@littlepinkcloud.invalid> - 2011-12-13 09:05 -0600
          Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-13 08:10 -1000
            Re: Readable code and refactoring for optimization anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-12-15 16:44 +0000
              Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-15 09:15 -1000
                Re: Readable code and refactoring for optimization anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-12-16 17:13 +0000
                Re: Readable code and refactoring for optimization "Elizabeth D. Rather" <erather@forth.com> - 2011-12-16 08:11 -1000
                Re: Readable code and refactoring for optimization anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-12-21 13:57 +0000
        Re: Readable code and refactoring for optimization anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-12-13 15:06 +0000
        Re: Readable code and refactoring for optimization Bernd Paysan <bernd.paysan@gmx.de> - 2011-12-13 16:18 +0100
          Re: Readable code and refactoring for optimization mhx@iae.nl (Marcel Hendrix) - 2011-12-14 15:49 +0200

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