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Algorithm::Munkres.3pm

NAME

     Algorithm::Munkres - Perl extension for Munkres' solution to 
     classical Assignment problem for square and rectangular matrices 
     This module extends the solution of Assignment problem for square
     matrices to rectangular matrices by padding zeros. Thus a rectangular 
     matrix is converted to square matrix by padding necessary zeros.
 
 

SYNOPSIS

use Algorithm::Munkres;

     @mat = (
          [2, 4, 7, 9],
          [3, 9, 5, 1],
          [8, 2, 9, 7],
          );
 
 

assign(\@mat,\@out_mat);

     Then the @out_mat array will have the output as: (0,3,1,2),
     where 
     0th element indicates that 0th row is assigned 0th column i.e value=2
     1st element indicates that 1st row is assigned 3rd column i.e.value=1
     2nd element indicates that 2nd row is assigned 1st column.i.e.value=2
     3rd element indicates that 3rd row is assigned 2nd column.i.e.value=0
 
 

DESCRIPTION

     Assignment Problem: Given N jobs, N workers and the time taken by 
     each worker to complete a job then how should the assignment of a 
     Worker to a Job be done, so as to minimize the time taken. 
 
         Thus if we have 3 jobs p,q,r and 3 workers x,y,z such that:
             x  y  z             
          p  2  4  7
          q  3  9  5
          r  8  2  9
         
         where the cell values of the above matrix give the time required
         for the worker(given by column name) to complete the job(given by 
         the row name) 
     
         then possible solutions are:    
                          Total
          1. 2, 9, 9       20
          2. 2, 2, 5        9
          3. 3, 4, 9       16
          4. 3, 2, 7       12
          5. 8, 9, 7       24
          6. 8, 4, 5       17
 
     Thus (2) is the optimal solution for the above problem.
     This kind of brute-force approach of solving Assignment problem 
     quickly becomes slow and bulky as N grows, because the number of 
     possible solution are N! and thus the task is to evaluate each 
     and then find the optimal solution.(If N=10, number of possible
     solutions: 3628800 !)
     Munkres' gives us a solution to this problem, which is implemented 
     in this module.
 
     This module also solves Assignment problem for rectangular matrices 
     (M x N) by converting them to square matrices by padding zeros. ex:
     If input matrix is:
          [2, 4, 7, 9],
          [3, 9, 5, 1],
          [8, 2, 9, 7]
     i.e 3 x 4 then we will convert it to 4 x 4 and the modified input 
     matrix will be:
          [2, 4, 7, 9],
          [3, 9, 5, 1],
          [8, 2, 9, 7],
          [0, 0, 0, 0]
 
 

EXPORT

     "assign" function by default.
 
 

INPUT

     The input matrix should be in a two dimensional array(array of 
     array) and the 'assign' subroutine expects a reference to this 
     array and not the complete array. 
     eg:assign(\@inp_mat, \@out_mat);
     The second argument to the assign subroutine is the reference 
     to the output array.
 
 

OUTPUT

     The assign subroutine expects references to two arrays as its 
     input paramenters. The second parameter is the reference to the
     output array. This array is populated by assign subroutine. This 
     array is single dimensional Nx1 matrix.
     For above example the output array returned will be:
      (0,
      2,
      1)
 
     where 
     0th element indicates that 0th row is assigned 0th column i.e value=2
     1st element indicates that 1st row is assigned 2nd column i.e.value=5
     2nd element indicates that 2nd row is assigned 1st column.i.e.value=2
 
 

SEE ALSO

     1. http://216.249.163.93/bob.pilgrim/445/munkres.html
 
     2. Munkres, J. Algorithms for the assignment and transportation 
        Problems. J. Siam 5 (Mar. 1957), 32-38
 
     3. FranA~Xois Bourgeois and Jean-Claude Lassalle. 1971.
        An extension of the Munkres algorithm for the assignment 
        problem to rectangular matrices.
        Communication ACM, 14(12):802-804
 
 

AUTHOR

     Anagha Kulkarni, University of Minnesota Duluth
     kulka020 <at> d.umn.edu
         
     Ted Pedersen, University of Minnesota Duluth
     tpederse <at> d.umn.edu
 
 

COPYRIGHT AND LICENSE

Copyright (C) 2007-2008, Ted Pedersen and Anagha Kulkarni

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.