comment on

I ran some benchmarks on this fibonacci code.
The JavaFan code is the fastest. My code is 2nd. There is no 3rd, 4th or 5th place. Things go "downhill" very fast (not just factor of 2x, 3x, but orders of magnitude).

#!/usr/bin/perl -w
use feature qw(say);
use Memoize;
use Benchmark;

=results:
Benchmark: timing 100000 iterations of JavaFan, Marshall, 
                                      Memoize, Recurse...
   JavaFan:  2 wallclock secs ( 2.00 usr +  0.00 sys =  2.00 CPU) 
               @ 49975.01/s (n=100000)
  Marshall:  6 wallclock secs ( 6.59 usr +  0.00 sys =  6.59 CPU) 
               @ 15165.30/s (n=100000)
   Memoize: 50 wallclock secs (49.45 usr +  0.25 sys = 49.70 CPU) 
               @ 2011.99/s (n=100000)
   Recurse: 644 wallclock secs (641.27 usr +  0.05 sys = 641.31 CPU) 
              @ 155.93/s (n=100000)
=cut              

timethese (100000,

 { JavaFan=> 
    q{
       sub fib  {
                   my $PHI = (1 + sqrt(5)) / 2;
                   int($PHI ** $_[0] / sqrt(5) + 0.5)
                 }
       foreach (0 .. 15)
       {
         # print fib($_), "\n";
          fib($_);
       }
     },
          
   Marshall =>
    q{
        foreach (1..15)
        {
           # print fibonacci($_), " ";
            fibonacci($_);
         }

         sub fibonacci
         {
             my $number = shift;
  
             my $cur_num   = 1;
             my $prev_num  = 1;
             my $sum;
         
             return 1  if ($number == 1 || $number == 2);
       
             $number -= 2;
     
             while ($number--)
             {
                $sum = $cur_num + $prev_num;
                $prev_num = $cur_num;
                $cur_num  = $sum;
             }     
             return $sum;
         }
     },
   
   Recurse =>
      q{
          foreach (1..15)
          {
            # print fibx($_), "\n";
              fibx($_);
          }
       
         # Compute Fibonacci numbers
           sub fibx 
           {
             my $n = shift;
             return $n if $n < 2;
             fibx($n-1) + fibx($n-2);
           }
      },
      
   Memoize =>
      q{
          memoize('fiby');
          foreach (1..15)
          {
             fiby($_);
            #print fiby($_);
             
          }
       
         # Compute Fibonacci numbers
           sub fiby 
           {
             my $n = shift;
             return $n if $n < 2;
             fiby($n-1) + fiby($n-2);
           }
      },        
 } 
);
[download]

In reply to Re: Explain Fibonacci one-liner ?? by Marshall
in thread Explain Fibonacci one-liner ?? by Anonymous Monk

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