Attempt to extract field 'iterations' from 'mxArray'

Hello! I need help. My problem is in Title. I use codegen for translate .m-code in mex.

    [xopt,zmin,exitflag,output,lambda] = linprog(C1,A,B,[],[],LB1,[],[],options);
    fprintf(1,Out1,xopt,zmin);
    fprintf(1,'ExitFlag= %d\nIterats= %d\n',exitflag,output.iterations);

How can I solve this problem?

Answer 1

[Grek Vardugin]

I solve it. First, I created a new structure with fields that exist in the output structure.

output = struct('iterations', 0, 'constrviolation', 0, 'message', '', 'algorithm', '', 'firstorderopt', 0);

Then I added the coder.varsize function for text fields.

coder.varsize('output.message', [1,100]);
coder.varsize('output.algorithm', [1,100]);

After

[xopt,zmin,exitflag,output,lambda] = linprog(C,A,B,Aeq,Beq,lb,ub,[],options);
fprintf(1,Out1,xopt,zmin);
fprintf(1,'\nExitFlag = %d\nIterats = %d\n',exitflag,num2str(output.iterations));

Answer 2

[Joh Hag]

hi, is output a struct? the mxArray is just the bare data and does not have such a field. have you tried to put the value in a separate variable such num_iterations = output.iterations? and then use this one in the fprintf command. this could help codegen to sort things out.

[Grek Vardugin]

Hi, Jon! Thank you for your answer! Yes, output is a struct, where output.iterations is integer type. My goal is to execute the linprog function and write some of its results to a file. In this case, write output.iterations.

[Joh Hag]

Did you try the trick with the temporary variable? where does the compilation actually fail? at the fprintf's or when you call linprog?

[Grek Vardugin]

Compilation failed then I use fprintf. If I use the disp function instead of fprintf, I get a similar error.