Ok, I give up.
I certainly agree that replacing 'memory access with cheap operator'
is a good idea and obviously would be faster.
Here's some snips of benchmarks comparing the two: 
@a=(1,2,3,0); $x=0; $m=4;
timethese(-10,{ ixwheel=> q{ $x = $a[$x] }
               modby2x1=> q{ $x = (++$x) & $m} });
 ixwheel: 434505.60/s
modby2x1: 391856.16/s

timethese(-10,{ ixwheel=> q{ $x=$a[$x] }
               modby2x2=> q{ $x++; $x &= $m }});
 ixwheel: 433011.28/s
modby2x2: 539474.07/s

[download]
Well, ok. For some reason the 2 statement version is much faster
than the 1 statement one (($x+1) was even slower than (++$x)!).
But now look what happens when they're used as an index: 
timethese(-10,{ ixwheelix=> q{ $b[ $x=$a[$x] ] = $x }
               modby2x2ix=> q{ $b[$x++] = $x; $x &= $m }});
 ixwheelix: 262030.67/s
modby2x2ix: 220259.36/s

[download]
Again, this seemed to be the fastest of the variations.

But then, I'm using perl 5.05003 on a sparc solaris, YMMV.

???????????,

p

In reply to Re: Re: Re: Re: Circular buffer instead of shift/push by petral
in thread Circular buffer instead of shift/push by petral

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