You might also try this :
sub Root2 {
my $num = shift;
my $root = shift;
my $iterations = shift || 10;
if ( $root == 0 ) { return 1 }
if ( $num < 0 ) { return undef }
my $current = Math::BigFloat->new();
my $guess = Math::BigFloat->new( $num / $root );
my $t=Math::BigFloat->new($guess**($root-1)); 1st version : WRONG ! sh
+ould be in the loop.
for ( 1 .. $iterations ) {
$current = $guess - ( $guess * $t - $num ) / ( $root * $t );
if ( $guess eq $current ) { last }
$t=Math::BigFloat->new($current**($root-1));
$guess = $current;
}
return $current;
}
The idea behind, is that '**' is MUCH slower than '*', so I exchange 2 '**' for one '**' and 2 '*'
It
seems indeed to speed things alot :
(I'm sure your numerous tests will make it sure ;-)
timethese(10,{
'Root'=> sub {Root(1000,60)},
'Root2'=> sub {Root2(1000,60)}});
gives as result :
Benchmark: timing 10 iterations of Root, Root2...
Root: 104 wallclock secs (104.38 usr + 0.01 sys = 104.39 CPU) @
0.10/s (n=10)
Root2: 15 wallclock secs (14.75 usr + 0.00 sys = 14.75 CPU) @ 0.68/s (n=10)
Root2: 97 wallclock secs (92.67 usr + 0.16 sys = 92.83 CPU) @
0.11/s (n=10)
UPDATE :
Corrected my code! I misplaced the $t calculation outside the loop,
which is wrong beccause $guess change inside the loop.
As you can see it's no more so fast...
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