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%    Copyright (c) 2004.  Takayuki Osogami.  All Rights Reserved.   %
%                                                                   %
% Permission to use, copy, modify, and distribute this source code  %
% and its documentation for any purpose, without fee, and without   %
% a written agreement, is hereby granted, provided that the above   %
% copyright notice, this paragraph and the following two paragraphs %
% appear in all copies, modifications, and distributions.           %
% Created by Takayuki Osogami, Department of Computer Science,      %
% Carnegie Mellon University.                                       %
%                                                                   %
% IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR ANY       %
% DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS   %
% SOURCE CODE AND ITS DOCUMENTATION, EVEN IF THE AUTHOR HAS BEEN    %
% ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.                        %
%                                                                   %
% THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,      %
% BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY     %
% AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOURCE CODE AND        %
% ACCOMPANYING DOCUMENTATION, IF ANY, PROVIDED HEREUNDER IS         %
% PROVIDED "AS IS."  THE AUTHOR HAS NO OBLIGATION TO PROVIDE        %
% MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.    %
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%
% Usage: [yes] = isPH2(m2,m3)
%
% Given normalized second and third moments, (m2,m3),
% the function returns if there exist a 2-phase PH distribution
% with the normalized second and third moment.
%
% author: Takayuki Osogami
%         Department of Computer Science
%         Carnegie Mellon University
%         osogami@cs.cmu.edu
% date: June 6, 2004

function [yes] = isPH2(m2,m3)

yes = 0;

%% If the input is not even a PH, return 0;

if( (m2 <= 1) || (m3 <= m2) )

     return;

end

%% Main:

if( m2 > 2 ) 

 if( m3 > 3/2 * m2 )

     yes = 1;

 end

elseif( m2 < 2 )

 if( (m2 >= 3/2) && (m3 <= 6*(m2-1)/m2) && (m3 >= (9*m2-12+3*(2-m2)*sqrt(2*(2-m2)))/m2) )

     yes = 1;

 end

end