In rashida.par's Recursive function to find X to the power n (http://www.go4expert.com/showthread.php?t=9307) I see that she intelligently used recursion to find the power of x to n. So, I was wondering whether we can do this iteratively also, I always do that - trying to find a iterative solution to a recursive one.
Being more of a Perl programmer than C, I wrote my code in Perl - can be understood by any programmer. I also benchmarked the recursive function to the iterative version.
Test run of the code:
I also benchmarked the recursive function to the iterative version to see which one performs better.
Result:
As we see here, the iterative version performs much better than the recursive one, the reason being the recursive version need more memory for function call stacks etc.
I hope this was helpful to you all.
Being more of a Perl programmer than C, I wrote my code in Perl - can be understood by any programmer. I also benchmarked the recursive function to the iterative version.
The Iterative Solution
Code: Perl
sub power_iterative
{
my ($x,$n) = @_; ## take in parameters
my $result = 1;
while($n--)
{
$result *= $x;
}
return $result;
}
Test run of the code:
Code: Perl
printf("\n %.4f to the power of % d is %.4f",$x,$n,power_iterative($x,$n));
Code:
[pradeep@go4expert perl_test]$ perl power_iterative.pl 4.0000 to the power of 10 is 1048576.0000
Benchmarking
I also benchmarked the recursive function to the iterative version to see which one performs better.
Code: Perl
use Benchmark;
sub power_iterative
{
my ($x,$n) = @_; ## take in parameters
my $result = 1;
while($n--)
{
$result *= $x;
}
return $result;
}
sub power_recursive
{
my ($x,$n) = @_; ## take in parameters
if ($x==0)
{
return 0;
}
elsif($n==0)
{
return 1;
}
elsif ($n>0)
{
return( $x* power_recursive($x,$n-1));
}
else
{
return ((1/$x)*power_recursive($x,$n+1));
}
}
my ($x,$n) = (4,10);
timethese(400000,{
'iterative'=> sub{my $power = power_iterative($x,$n);},
'recursive'=> sub{my $power = power_recursive($x,$n);}});
Result:
Code:
[pradeep@go4expert perl_test]$ perl power_iterative.pl Benchmark: timing 400000 iterations of iterative, recursive... iterative: 2 wallclock secs ( 1.28 usr + 0.00 sys = 1.28 CPU) @ 312500.00/s (n=400000) recursive: 6 wallclock secs ( 5.90 usr + 0.00 sys = 5.90 CPU) @ 67796.61/s (n=400000)
I hope this was helpful to you all.
