Hello BrowserUk,

As usual, I'm late to the table, but I've found in my *nix environments that using 'elsif' does improve the performance and adding some minimal binary splitting also improved the performance of your subroutine. I benchmarked both your original and my re-work and results are at the bottom. Obviously if the inputs are better known you could improve the break points. Hope this spurs your imagination a little.

use strict;
use warnings;
use Benchmark qw(:all);

my @input = ( 25000, 50000, 150000, 225000, 300000, 600000, 1200000, 3
+600000,
              5400000, 10800000, 21600000, 43200000, 64800000, 1296000
+00,
              216000000, 432000000, 864000000, 1728000000, 3024000000,
              6048000000, 12096000000, 31557600000, 63115200000, 78894
+000000,
              157788000000, 315576000000,
             );

my @newinput = ();

for ( 0 .. $#input )
{    $newinput[$_] = $input[$_] - 11;     #     print $newinput[$_],"\
+n";    #    Testing
}

#    print $#newinput,"\n";        # size of input array

## Make sure both subroutines return same results!
for my $no ( 0 .. $#newinput )
{   my $r1 = &lookup_org ( $newinput[ $no ] );
    my $r2 = &lookup_new ( $newinput[ $no ] );
    if ( $r1 != $r2 ) { print "$no|$r1|$r2|\n"; exit(1); }
    #    print "$no|$r1|$r2|\n";     # Testing
}

timethese ( -2 ,
        {
           case1 => sub { &lookup1 },
           case2 => sub { &lookup2 },
        },
    );


sub lookup1
{    for ( 0 .. $#newinput )
    {    lookup_org ( $newinput[ $_ ] ); }
}

sub lookup2
{    for ( 0 .. $#newinput )
    {    lookup_new ( $newinput[ $_ ] ); }
}


sub lookup_org {
    my $v = shift;
    if( $v <        25000 ) { return        2500; }
    if( $v <        50000 ) { return        5000; }
    if( $v <       150000 ) { return       12500; }
    if( $v <       225000 ) { return       25000; }
    if( $v <       300000 ) { return       37500; }
    if( $v <       600000 ) { return       60000; }
    if( $v <      1200000 ) { return      120000; }
    if( $v <      3600000 ) { return      300000; }
    if( $v <      5400000 ) { return      600000; }
    if( $v <     10800000 ) { return      900000; }
    if( $v <     21600000 ) { return     1800000; }
    if( $v <     43200000 ) { return     3600000; }
    if( $v <     64800000 ) { return     7200000; }
    if( $v <    129600000 ) { return    10800000; }
    if( $v <    216000000 ) { return    21600000; }
    if( $v <    432000000 ) { return    43200000; }
    if( $v <    864000000 ) { return    86400000; }
    if( $v <   1728000000 ) { return   172800000; }
    if( $v <   3024000000 ) { return   345600000; }
    if( $v <   6048000000 ) { return   604800000; }
    if( $v <  12096000000 ) { return  1209600000; }
    if( $v <  31557600000 ) { return  2629800000; }
    if( $v <  63115200000 ) { return  5259600000; }
    if( $v <  78894000000 ) { return  7889400000; }
    if( $v < 157788000000 ) { return 15778800000; }
    else { return 31557600000; }
}

sub lookup_new {
   my $v = shift;
    if ( $v >= 64800000 )
   {    if   ( $v <    129600000 ) { return    10800000; }
        elsif( $v <    216000000 ) { return    21600000; }
        elsif( $v <    432000000 ) { return    43200000; }
        elsif( $v <    864000000 ) { return    86400000; }
        elsif( $v <   1728000000 ) { return   172800000; }
        elsif( $v <   3024000000 ) { return   345600000; }
        elsif( $v <   6048000000 ) { return   604800000; }
        elsif( $v <  12096000000 ) { return  1209600000; }
        elsif( $v <  31557600000 ) { return  2629800000; }
        elsif( $v <  63115200000 ) { return  5259600000; }
        elsif( $v <  78894000000 ) { return  7889400000; }
        elsif( $v < 157788000000 ) { return 15778800000; }
        else {    return 31557600000; }
    }
    else
    {   if   ( $v <        25000 ) { return        2500; }
        elsif( $v <        50000 ) { return        5000; }
        elsif( $v <       150000 ) { return       12500; }
        elsif( $v <       225000 ) { return       25000; }
        elsif( $v <       300000 ) { return       37500; }
        elsif( $v <       600000 ) { return       60000; }
        elsif( $v <      1200000 ) { return      120000; }
        elsif( $v <      3600000 ) { return      300000; }
        elsif( $v <      5400000 ) { return      600000; }
        elsif( $v <     10800000 ) { return      900000; }
        elsif( $v <     21600000 ) { return     1800000; }
        elsif( $v <     43200000 ) { return     3600000; }
        elsif( $v <     64800000 ) { return     7200000; }
    }
}

__END__

Results: 1st is worst time, 2nd is best time

Benchmark: running case1, case2 for at least 2 CPU seconds...
   case1:  2 wallclock secs ( 2.24 usr +  0.00 sys =  2.24 CPU) @ 4799
+9.55/s (n=107519)
   case2:  3 wallclock secs ( 2.06 usr +  0.00 sys =  2.06 CPU) @ 6088
+8.83/s (n=125431)

Benchmark: running case1, case2 for at least 2 CPU seconds...
    case1:  3 wallclock secs ( 2.32 usr +  0.00 sys =  2.32 CPU) @ 486
+57.33/s (n=112885)
    case2:  2 wallclock secs ( 2.24 usr +  0.00 sys =  2.24 CPU) @ 610
+86.61/s (n=136834)
[download]

Best Regards...Ed

---

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