Error in dual simplex algorithm

5 次查看（过去 30 天）

SUSHMA MB 2015-6-20

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/224634-error-in-dual-simplex-algorithm

评论： cwshep 2015-6-20

I have a code for dual simplex algorithm, given below. But i am not able to rectify the error shown by this code. I want to run the code for the following constraints, type = 'min'; c = [-2 3 4]; A = [-1 –1 –1;2 2 2]; b = [-1;4]; "subs = dsimplex(type, c, A, b)" . Please help me to sort the error.

 function varargout = dsimplex(type, c, A, b)
% The Dual Simplex Algorithm for solving the LP problem
% min (max) z = c*x
% Subject to Ax >= b
% x >= 0
%
if type == 'min'
 mm = 0;
else
 mm = 1;
 c = -c;
end
str = 'Would you like to monitor the progress of computations?';
A = -A;
b = -b(:);
c = c(:)';
[m, n] = size(A);
A = [A eye(m) b];
A = [A;[c zeros(1,m+1)]];
question_ans = questdlg(str,'Make a choice Window','Yes','No','No');
if strcmp(question_ans,'Yes')
 p1 = 'y';
else
 p1 = 'n';
end
if p1 == 'y'
 disp(sprintf('\n\n Initial tableau'))
 A
  disp(sprintf(' Press any key to continue ...\n\n'))
 pause
end
subs = n+1:n+m;
[bmin, row] = Br(b);
tbn = 0;
while ~isempty(bmin) & bmin < 0 & abs(bmin) > eps
 if A(row,1:m+n) >= 0
 disp(sprintf('\n\n Empty feasible region\n'))
 varargout(1)={subs(:)};
 varargout(2)={A};
 varargout(3) = {zeros(n,1)};
 varargout(4) = {0};
 return
 end
 col = MRTD(A(m+1,1:m+n),A(row,1:m+n));
 if p1 == 'y'
 disp(sprintf(' pivot row-> %g pivot column-> %g',... 
     row,col))
 end
 subs(row) = col;
 A(row,:)= A(row,:)/A(row,col);
 for i = 1:m+1
 if i ~= row
 A(i,:)= A(i,:)-A(i,col)*A(row,:);
 end
 end
 tbn = tbn + 1;
 if p1 == 'y'
 disp(sprintf('\n\n Tableau %g',tbn))
 A
 disp(sprintf(' Press any key to continue ...\n\n'))
 pause
 end
 [bmin, row] = Br(A(1:m,m+n+1));
end
x = zeros(m+n,1);
x(subs) = A(1:m,m+n+1);
x = x(1:n);
if mm == 0
 z = -A(m+1,m+n+1);
else
 z = A(m+1,m+n+1);
end
disp(sprintf('\n\n Problem has a finite optimal solution\n\n'))
disp(sprintf('\n Values of the legitimate variables:\n'))
for i=1:n
 disp(sprintf(' x(%d)= %f ',i,x(i)))
end
      disp(sprintf('\n Objective value at the optimal point:\n'))
      disp(sprintf(' z= %f',z))
disp(sprintf('\n Indices of basic variables in the final tableau:'))
varargout(1)={subs(:)};
varargout(2)={A};
varargout(3) = {x};
varargout(4) = {z};