Benchmark array passing Question

rakshas has asked for the wisdom of the Perl Monks concerning the following question:

Hi,

I have written a binary search program. It runs fine, and I want to see the Bench marking on it. Below is the code. I am sending the an array an the value to the binarysearch function which is supposed to calculate the search. However, the values are not going to the function. Please advice me

use warnings;
use strict;
use bytes;
use Benchmark;



#**************************Define the variables***********************
+*************
my @binarysearcharray=('1','2','3','4','5');
my $binarysearchkey=4;

sub binarysearch{
my ($array,$key)=@_;

my @array=@$array;

my ($low,$high) = (0,scalar(@$array));  # computes the length of the a
+rray and gives it to $high



while($low <= $high){
    my $mid= int(($low+$high)/2);
    print "The New mid is : $mid\n";
    
    if($array[$mid] < $key){
        
        $low = $mid + 1;
        print " Calculating Lower Bound\n";
        
    }
    elsif($array[$mid] == $key)
    {
        
        print "Match found at position $array[$mid]\n";
        last;
    }
    else #($array[$high] > $key)
    {
        
        $high=$mid-1;
        print "Calculating Upper Bound\n";
        
    }
    
    
}
  
}
[download]

####################Bench Marking Area########################### timethese(4,{binarysearch => 'binarysearch(\@binarysearcharray,2)'});

Output

Benchmark: timing 4 iterations of binarysearch... The New mid is : 0 Calculating Lower Bound The New mid is : 0 Calculating Lower Bound The New mid is : 0 Calculating Lower Bound The New mid is : 0 Calculating Lower Bound binarysearch: 0 wallclock secs ( 0.00 usr + 0.00 sys = 0.00 CPU) (warning: too few iterations for a reliable count)

Comment on Benchmark array passing Question Download Code

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Re: Benchmark array passing Question by kennethk (Abbot) on Jun 04, 2012 at 16:55 UTC
You have a scope issue. You can see this if you change your array declaration from `my @binarysearcharray=...` to `our @binarysearcharray=...`. The eval for the benchmark occurs in Benchmark package, and variables declared with my are not visible outside your current scope, in contrast to our. For a little more description of scope, see Private Variables via my(). Please note that if you include output in a benchmarking run, the i/o is likely to invalidate your conclusions. #11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.	[reply] [d/l] [select]
Re^2: Benchmark array passing Question by rakshas (Novice) on Jun 04, 2012 at 17:01 UTC
Works Like a Charm now!!!! Thanks!!!!!	[reply]
Re: Benchmark array passing Question by SuicideJunkie (Vicar) on Jun 04, 2012 at 17:03 UTC
If you're benchmarking, one comment is that you're wasting time and memory making a copy of the input array. You can drop `my @array=@$array;` and then change your `$array[...`'s into `$array->[...`'s Also, your brackets aren't lining up right. I don't think there are any styles that would allow for: `} }` [download]	[reply] [d/l] [select]
Re: Benchmark array passing Question by jwkrahn (Abbot) on Jun 04, 2012 at 22:27 UTC
`my ($low,$high) = (0,scalar(@$array)); # computes the length of the a +rray and gives it to $high` [download] You have an off-by-one error. The value `scalar(@$array)` is not a valid index to any of the values in `@$array`. `my ($low,$high) = (0,$#$array); # computes the length of the array an +d gives it to $high` [download]	[reply] [d/l] [select]