in reply to optimizing the miller-rabin algorithm

I'm not sure I can help with your question. But you do say you are doing this in part to learn Perl, so I'll make a few (kindly meant) comments about your code.

First, always add use strict; use warnings; to your code. They will save you much grief and tearing of hair

Avoid C style for loops. For example replace

for (my $n=91001; $n<93000; $n++)

with:

for my $n (91001..93000)

Do not use $a and $b as general purpose variables. They are magical and are used in the context of sort.

DWIM is Perl's answer to Gödel

Replies are listed 'Best First'.
Re^2: optimizing the miller-rabin algorithm
by punklrokk (Scribe) on May 16, 2006 at 01:57 UTC
    If I use your version of a For Loop, how do I tell it to iterate two steps instead of one?

    JP Bourget (punklrokk) MS Information and Security Rochester Institute of Technology Rochester, NY
[reply]

      Either use the C style for loop in that case or, if appropriate, do something like for ($start/2..$end/2) with $start and $end both even (but that's rather clunky!).

      The Perl style for is very good for iterating over lists so you can do something like for (1.5, 2..4, @moreNumbers). Generally you should think Perl style for first, then C style if you really need it.

      DWIM is Perl's answer to Gödel
[reply]
[d/l]
[select]

      You could do 

      for (0..(5-1)/2) {  # 1..5, step 2
   my $i = $_*2 + 1;
   ...
}

      [download]

      but you're probably better off falling back to a C-style loop in that case.

      As an aside, the above trick is particularly useful when dealing with floats. 

      >perl -le "for (my $i=0; $i<10; $i+=0.1) { print $i }"
...
8.79999999999998
8.89999999999998
8.99999999999998
9.09999999999998
9.19999999999998
9.29999999999998
9.39999999999998
9.49999999999998
9.59999999999998
9.69999999999998
9.79999999999998
9.89999999999998
9.99999999999998

>perl -le "for (0..99) { my $i = $_ / 10; print $i }"
...
8.8
8.9
9
9.1
9.2
9.3
9.4
9.5
9.6
9.7
9.8
9.9

      [download]
[reply]
[d/l]
[select]

In Section Seekers of Perl Wisdom