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Re: Merge CIDRs

by Dominus (Parson)
on Oct 13, 2001 at 20:50 UTC ( #118673=note: print w/replies, xml ) Need Help??

in reply to Merge CIDRs

I think your original suggestion, of using Net::CIDR::cidr2range and merging the ranges end-to-end, was better. Your new program seems to be slower than the one I wrote following your Net::CIDR suggestion. Here's my program for comparison:
#!/usr/bin/perl use Net::CIDR 'cidr2range', 'range2cidr'; my @ranges; my ($cur_start, $cur_end, $cs, $ce); while (<>) { chomp; my @r = cidr2range($_); my ($r_start, $r_end) = split /-/, $r[0]; my ($rs, $re) = map {inet_to_n($_)} $r_start, $r_end; if (! defined $cur_start) { ($cur_start, $cur_end) = ($r_start, $r_end); ($cs, $ce) = ($rs, $re); } else { if ($rs == $ce + 1) { $cur_end = $r_end; $ce = $re; } else { print join "\n", range2cidr("$cur_start-$cur_end"), ""; ($cur_start, $cur_end) = ($r_start, $r_end); ($cs, $ce) = ($rs, $re); } } } continue { print STDERR "$. records processed\n" if $. % 1000 == 0; } print join "\n", range2cidr("$cur_start-$cur_end"), "" if defined $cur_start; sub inet_to_n { unpack "N", pack "C4", split /\./, shift(); }
I ran your program on and waited three minutes. Then I started my program. My program finished first.

Of course, I might have made a mistake in the benchmarking somewhere.

Mark Dominus
Perl Paraphernalia

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Re: Re: Merge CIDRs
by merlyn (Sage) on Oct 15, 2001 at 05:44 UTC
    You need to sort by start address. You're lucky that your input data was already sorted by such.

    Also, you have to look for $rs <= $ce + 1 rather than $rs == $ce + 1, or you end up not coalescing things like 0-7 (0.0/3), 4-7 (4.0/2), which should just get swallowed.

    -- Randal L. Schwartz, Perl hacker

      Says merlyn:
      You need to sort by start address. You're lucky that your input data was already sorted by such.
      No, I'm not. My original problem specification guaranteed sorted input.

      Anyway, those changes wouldn't slow down the program so much that I'd prefer to use the code you posted above. But you said the code above was an order of magnitude faster, not an order of magnitude slower, so I wonder what's up? Someone made a mistake, and I'm less than 50% confident that it was you.

      Mark Dominus
      Perl Paraphernalia

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