MATLAB: Fopen and fprintf do not work within parfor or smpd running on grid

Question

Hello everyone,

I met a problem to use fopen and fprintf within parfor or smpd when I run my codes on grid. Here are my codes:

    spmd
fid = fopen(sprintf( 'worker_%d.csv', labindex ),'w');
fprintf(fid,'%s\r\n',vector1);
fclose(fid);
...
end

OR

parfor i=1:100
t = getCurrentTask(); 
fid = fopen(sprintf( 'worker_%d.csv', t.ID ),'w');
fprintf(fid,'%s\r\n',vector1);
fclose(fid);
...
end

Neither one would work, and both of them will generated the similar error messages:

spmd:

??? Error using ==> spmd_feval at 8
Error detected on lab(s) 2 15 16
Error in ==> BruteForce2>(spmd) at 103
spmd
Error in ==> BruteForce2 at 103
spmd
Caused by:
      Invalid file identifier.  Use fopen to generate a valid file identifier.
      Error stack:
      BruteForce2>(spmd body) at 105
      Invalid file identifier.  Use fopen to generate a valid file identifier.
      Error stack:
      BruteForce2>(spmd body) at 105
      Invalid file identifier.  Use fopen to generate a valid file identifier.
      Error stack:
      BruteForce2>(spmd body) at 105

PARFOR:

??? Error using ==> parallel_function at 598
Error in ==> BruteForce2>(parfor body) at 146
Invalid file identifier.  Use fopen to generate a valid file identifier.
Error in ==> BruteForce2 at 105
parfor i = 1:g

The problem is my fopen, fid returns -1. The codes are running ok with local workers. So would it be some writing permission issues? I would like to know what the problem is, and where our admin should change on his side. Could anyone give me any suggestion? Thanks a lot!

Rui

Answer 1

fname = sprintf( 'worker_%d.csv', t.ID );
[fid, message] = fopen(fname, 'w');
if fid < 0;
 fprintf(2, 'failed to open "%s" because "%s"\n', fname, message);
 %and here, get out gracefully
end