Variables from a .mat file, loaded with "coder.load" in a mex-file, remain equal when I change the value of the content of the mat.file

Hi everyone!

This is my first time asking a question, so I hope I can give you a good description of my problem so someone can help me.

I have created a mex file from a .m.

The mexfile read a couple of variables from a .mat file using the function coder.load('name.mat') :

DatosInput = coder.load('name');
m_est = DatosInput.mest;
R_est = DatosInput.rs;
L_est_disper = DatosInput.lls;
L_est_mag_1 = DatosInput.lm;
m_rot = DatosInput.m_rot;
R_rot = DatosInput.rpr;
L_rot_disper = DatosInput.mest;
Par_resistenteValor =DatosInput.Tres;
J_inercia = DatosInput.J;
p = DatosInput.p;
fmostens = DatosInput.fmostens;
tfinal = DatosInput.tfinal;
U_aux = DatosInput.U_linea;

The thing is that the value of the variables stored in "name.mat" are not always the same (in size and value), because externaly everytime a different .mat file is generated, however, the amount of variables are always the same.

The problem is that, once I compile the mex-file using MATLAB Coder and change the original values of the name.mat, the mexfile continue operating with the original values which with the mex-file was created during the compiling.

Thank you very much.

[dpb]

More than likely this is a path/file location issue -- I'd guess the location being looked for in the mex file is not the same place as the copy of the file you're changing is located so you're not changing the actual file that is being used.

Try using a fully-qualified file name...

[Jorge Bonet Jara]

Thank you for the reponse. I've tried to used the full path name but still does not work. So, I tested the code with a certain parameters in the .mat file. Then I changed some of those parameters and saved the .mat with the same name and in the same location. Called the mex function (which I've created from a .m) and it is still using the old parameters in the mat.file. It is like, the initial parameters stored in the .mat file at the moment of the creation of the mex file remains permanently in the function.

I don't know if the problem is using coder.load. I use this function because it seemed to give me a quick response when I called the mex function, rather than a simple load.

Maybe the problem is related with that I've found in: https://es.mathworks.com/help/simulink/slref/coder.load.html

Limitations

• Arguments to coder.load must be compile-time constants.

Does it mean that once they are compile, they value remains constant?

Thank you again.

[dpb]

Well, you used the text string 'name' which is compile-time constant so that is OK.

The next step would be to be sure you're actually then executing the code you think you are...what does

which -all yourfunctionname

show? Is that the one you think you're executing?

I don't have Simulink so can't test behavior here but doesn't seem as tho the data should itself be stored, no.

[Jorge Bonet Jara]

I did what you mentioned, and I made it sure that it was the file I was executing. But it seems the problem is not there.

When I execute my function as an .m file, there is no problem, any change I make in the name.mat is reflected when I call the function, nevertheless, this does not happen when instead of calling de .m function I call the mex file, even when the mex file is compile directly without any change from the .m file.

To clarify more, I add an simplified version of my code:

function GeneralCode()
   
   %Anytime the loops makes an increment, new values for the same variables are stored in name.mat
   for n=1:10
   %........
   %.......
   %.......
   % The name.mat is created and saved in C:\Users\Joan\Desktop\Simulador\FASES INDEPENDIENTES\Buenos seguros\Mixto Mejorado
   %......
   % Then the function who makes all the heavy computations is called
   [I,Torque,Omega,I_rot] = heavyComputation();
   end

end

When "heavyComputation" is a .m file, everything works perfect, any change in name.mat is reflected in the function.

When "heavyComputation" is a mex file (created from the "heavyComputation" .m file), any change in name.mat is NOT reflected in the function, so no matter the content of name.mat it always give the same outputs.

Thank you for your time, sir.

[dpb]

Are you sure the compilation process is deleting the old object file(s) when building a new .mex file? No chance it's silently failing the compile step and somehow relinking an old object file or somesuch? Is there a "verbose" option on the build step to watch what occurs?

It's bizarre symptom but there has to be an explanation; just don't see what would cause the particular one.

This one is probably worth a bug/support request to official TMW support at <[e-mail]> or use the link at the top of page for contact.

[Jorge Bonet Jara]

I 99% sure that any old file is deleted, I checked it several times. I am starting thinking that the problem is that mex files compiles throughout MATLAB CODER can't run-time load .mat files. They can the first time is compiled, making the variables stored in the .mat permanentes in the mex code, but once compiled, it seems it doens't call the function load again to get new values.

I will contact with TMW support. Thank you for your help.

[dpb]

After re-reading the documentation link, I see now that is indeed the documented bethavior.

It's not totally clear that's what they mean I think on first reading because one just doesn't really expect that kind of behavior for a function with the name and the way the regular load function works.

To do so at run time will take a different route--not sure what can be used in the environment you're working in, though, for specifics.

[Jorge Bonet Jara]

I agree with you that it is not totally clear. But, anyway, it seems that this is the current behaviour of the function load when you compile the function as a mex file. Whatever, I open a query to the matlab support service, maybe there is another alternative.

pd: I tested with coder.load and load, and both of them have the same behaviour.

Thank you very much for your time.

Edit:

I contacted matlab support and they gave a solution that works:

 %#codegen
coder.varsize('Parametros2.Conexion')
coder.varsize('Parametros2.U_linea')
coder.varsize('Parametros2.tout')
Parametros2=load('C:\Users\Joan\Desktop\Simulador\FASES INDEPENDIENTES\Buenos seguros\SeñalesYDatosSim\Parametros2.mat');

m_est = Parametros2.mest;
R_est = Parametros2.rs;
L_est_disper = Parametros2.lls;
L_est_mag_1 = Parametros2.lm;
m_rot = Parametros2.m_rot;
R_rot = Parametros2.rpr;
L_rot_disper = Parametros2.lplr;
Par_resistenteValor =Parametros2.Tres;
J_inercia = Parametros2.J;
p = Parametros2.p;
fmostens = Parametros2.fmostens;
tfinal = Parametros2.tfinal;
U_aux = Parametros2.U_linea;
Conexion = Parametros2.Conexion;