1## Copyright (C) 2012 Moreno Marzolla 2## 3## This file is part of the queueing toolbox. 4## 5## The queueing toolbox is free software: you can redistribute it and/or 6## modify it under the terms of the GNU General Public License as 7## published by the Free Software Foundation, either version 3 of the 8## License, or (at your option) any later version. 9## 10## The queueing toolbox is distributed in the hope that it will be 11## useful, but WITHOUT ANY WARRANTY; without even the implied warranty 12## of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13## General Public License for more details. 14## 15## You should have received a copy of the GNU General Public License 16## along with the queueing toolbox. If not, see <http://www.gnu.org/licenses/>. 17 18## -*- texinfo -*- 19## 20## @deftypefn {Function File} {[@var{result} @var{err}] =} ctmcchkQ (@var{Q}) 21## 22## @cindex Markov chain, continuous time 23## 24## If @var{Q} is a valid infinitesimal generator matrix, return 25## the size (number of rows or columns) of @var{Q}. If @var{Q} is not 26## an infinitesimal generator matrix, set @var{result} to zero, and 27## @var{err} to an appropriate error string. 28## 29## @end deftypefn 30 31## Author: Moreno Marzolla <moreno.marzolla(at)unibo.it> 32## Web: http://www.moreno.marzolla.name/ 33 34function [result err] = ctmcchkQ( Q ) 35 36 persistent epsilon = 100*eps; 37 38 if ( nargin != 1 ) 39 print_usage(); 40 endif 41 42 result = 0; 43 err = ""; 44 45 if ( !issquare(Q) ) 46 err = "P is not a square matrix"; 47 return; 48 endif 49 50 if (any(Q(~logical(eye(size(Q))))<0) || ... # there is any negative non-diagonal element 51 norm( sum(Q,2), "inf" ) > epsilon ) 52 err = "Q is not an infinitesimal generator matrix"; 53 return; 54 endif 55 56 result = rows(Q); 57endfunction 58%!test 59%! Q = [0]; 60%! [result err] = ctmcchkQ(Q); 61%! assert( result, 1 ); 62%! assert( err, "" ); 63 64%!test 65%! N = 10; 66%! Q = ctmcbd(rand(1,N-1),rand(1,N-1)); 67%! [result err] = ctmcchkQ(Q); 68%! assert( result, N ); 69%! assert( err, "" ); 70 71%!test 72%! Q = [1 2 3; 4 5 6]; 73%! [result err] = ctmcchkQ(Q); 74%! assert( result, 0 ); 75%! assert( index(err, "square") > 0 ); 76 77%!test 78%! N = 10; 79%! Q = ctmcbd(rand(1,N-1),rand(1,N-1)); 80%! Q(2,1) = -1; 81%! [result err] = ctmcchkQ(Q); 82%! assert( result, 0 ); 83%! assert( index(err, "infinitesimal") > 0 ); 84 85%!test 86%! N = 10; 87%! Q = ctmcbd(linspace(1,N-1,N-1),linspace(1,N-1,N-1)); 88%! Q(1,1) += 7; 89%! [result err] = ctmcchkQ(Q); 90%! assert( result, 0 ); 91%! assert( index(err, "infinitesimal") > 0 ); 92