Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl: the Markov chain saw
 
PerlMonks  

comment on

( [id://3333]=superdoc: print w/replies, xml ) Need Help??
Conjuring on an adjacency matrix (thanks to Math::MatrixReal), this snippet finds every couple of nodes (i, j) such that there's a path from i to j. The matrix $sum is called transitive closure of the graph $graph.
#!/usr/bin/perl # Transitive closure of a directed graph use strict; use Math::MatrixReal; my $n = 4; # Matrix' size my $graph = Math::MatrixReal->new_from_string( <<'MATRIX' ); [ 0 1 0 1 ] [ 0 0 1 0 ] [ 0 0 0 0 ] [ 1 1 0 0 ] MATRIX my $sum = $graph->shadow(); my $p = $graph->shadow(); $p->one(); # "One Ring to rule them all, One Ring to find them..." # Sum of A^i, for i = 0..n-1 (A is the adjacency matrix of our graph) foreach (0 .. ($n - 1)) { $p = $p * $graph; $sum = $sum + $p; } # Finished. # Now we print every couple (i, j) such that # there's a path from i to j. foreach my $i (1..$n) { foreach my $j (1..$n) { print "There's a path from $i to $j.\n" if $sum->element( $i, +$j ); } }

In reply to Transitive closure by larsen

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or How to display code and escape characters are good places to start.
Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Chatterbox?
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others browsing the Monastery: (3)
As of 2024-04-20 01:35 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found