Invalid file identifier in Parfor loop

How to correct this error when using the parfor loop? Any suggestion to solve this issue? Thanks.

Invalid file identifier. Use fopen to generate a valid file identifier.

filename01 = "D:\...\testParfor"; % filename01 file parth 

parfor j = 1:nk2_node

        % File path
        filename_HD = sprintf('%s%s%d',filename01,"\zone_case0\profile_",j); 
        Cal_cont = HD_Nod_Inf(filename_HD);
        ...
 end
 
    
    

[xiaohuo]

Error using HD_Nod_Inf (line 7)

Invalid file identifier. Use fopen to generate a valid file identifier.

function Cal_water_cont = HD_Nod_Inf(filename_HD)
% Read the values in "Nod.out" file
    filename_Nod_sub = sprintf('%s%s',filename_HD,"\Nod.out");

    fidin_Nod_sub=fopen(filename_Nod_sub,'r+');
    Line_nod_sub=0;
    while ~feof(fidin_Nod_sub)    
        Line_nod_sub=Line_nod_sub+1;
        newtline_Nod_sub{Line_nod_sub}=fgetl(fidin_Nod_sub);  
    end
    fclose(fidin_Nod_sub);
    
    for i=1:199 
        k = i + Line_nod_sub-1-199;
        Cal_cont(i,1:22) = str2num(newtline_Nod_sub{k});
    end

end 

[Walter Roberson]

We recommend that you use fullfile() rather than string concatenation to build file names.

    filename_Nod_sub = fullfile(filename_HD, "Nod.out");

and

    filename_HD = fullfile(filename01, "zone_case0", "profile_"+j); 

[xiaohuo]

Error using HD_Nod_Inf (line 8)

Invalid file identifier. Use fopen to generate a valid file identifier.

The code still does not wrok for "while ~feof(fidin_Nod_sub)"

function ...
    
while ~feof(fidin_Nod_sub) % Invalid file identifier. Use fopen to generate a valid file identifier.
    
    
    ...
end

[Walter Roberson]

Change

    fidin_Nod_sub=fopen(filename_Nod_sub,'r+');

to

    [fidin_Nod_sub, msg] = fopen(filename_Nod_sub,'r+');
    if fidin_Nod_sub < 0
        error('Could not open file "%s" because "%s"', filename_Nod_sub, msg);
    end

[xiaohuo]

I test this funtion seperately, it works well. But the errors occurs ... in parfor loop.

Error using HD_Nod_Inf (line 22)

Array indices must be positive integers or logical values.

function Cal_water_cont = HD_Nod_Inf(filename_HD)
    ...
    for i=1:199 
        k = i + Line_nod_sub-1-199;
        Cal_cont(i,1:22) = str2num(newtline_Nod_sub{k}); %  error
    end
    ...
end'
        

[Walter Roberson]

That code assumes that you were able to read at least 399 lines from the file, and that you want to skip the first 200 lines.

If that is what you are trying to do, then I would suggest you replace your current function, to become:

fopen() like before

fmt = repmat('%f', 1, 22);
Cal_cont = cell2mat(textscan(fidin_Nod_sub, fmt, 'HeaderLines', 200));
fclose(fidin_Nod_sub)

[xiaohuo]

No, I wanted to read the last 199 lines from the end of file (excpet the last line).

============

Line(1)

...

Line( n)

Line (n+1)

...

Line (n +199)

Line 200

[Walter Roberson]

    for i=1:199 
        k = i + Line_nod_sub-1-199;
        Cal_cont(i,1:22) = str2num(newtline_Nod_sub{k}); %  error
    end

Suppose that 50 lines were read, so Line_nod_sub = 50. First iteration of the loop, i is 1, and k = 1 + 50 - 1 - 199 which is 51-200 which is -149 . Out of range.

Suppose that 205 lines were read, so Line_nod_sub = 205. First iteration of the loop, i is 1, and k = 1 + 205-1-199 = 6, which is okay. Last iteration of the loop, i is 199, and k = 199 + 205 - 1 - 199 = 204, which looks okay.

So I guess your loop might be okay -- but not until after you enforce that Line_nod_sub is at least 200.

[xiaohuo]

Yes, I also think so.

The reason why the code does not work is that the exe fails to run the model. So there is no output values in that file.

Thanks for your help and time.