coder.ceva​l('printf'​,....) does not print a message instantaneously

Hi! I need to print a message every few iterations during a simulation to control current state of the simulation. Since the m-file is designated for C-code generation using codegen, I use coder.ceval('printf',...) method. When I verify the compiled C-code using .mex function, none of the messages is printed during the simulation. Instead, all messages are printed at once after the simulation finishes. How can I force codegen to print a message instanteneously? Does anything similar to drawnow exist for coder.ceval('printf',..)? Anyone's help is appreciated!

Answer 1

[Friedrich]

Hi,

as long you stay with mex you can do a

mexEvalString("drawnow");

So a

coder.ceval('mexEvalString', '"drawnow"')

This will give the MATLAB Thread enough time to flush the buffer and to display the data.

In the case you want to generate code not for mex only you can use the coder.target to differentiate between those cases during the code generation process:

if strcmp('mex',coder.target)

    coder.ceval('mexEvalString', '"drawnow"')
end

[Tomas Jurena]

Thank you for your answer, but unfortunately this did not help. Here is my code:

matlab_run = isempty(coder.target);
mex_run = strcmp('mex',coder.target);
.       .       .       .      .
.       .       .       .      .
.       .       .       .      .
if matlab_run
  fprintf('some message');
else
  coder.ceval('printf',C_formatted_message);
  if mex_run
    coder.ceval('mexEvalString','"drawnow"');
  end
end

It still does not print messages during the simulation. Is anything wrong in the code? Note that when the generated C-code is executed from a main function, messages are printed to the console instantaneously.

Answer 2

[Tomas Jurena]

OK, I've finally figured it out with Friedrich's help. The argument of coder.ceval must be a C-formatted string, i.e.

C_command = ['drawnow' char(0)];
coder.ceval('printf',C_formatted_message);
coder.ceval('mexEvalString',C_command);

[Juan Rojas]

how do you create the C_formatted_message?

In my case I use printf with a file stream as: coder.ceval('printf',fid,s11,s12,int32(i));

Where fid was declared as: fid = coder.opaque('FILE *','NULL');