matlab parallel computing : the variable in a parfor is not classified

Question

All,

I met a very interesting situation on my parfor run on matlab, and following is my question.

fid = 'test.nc';
temp = ncread(fid,'temp');
[s1,s2,s3] = size(temp);

for m = 1 : 100
   parfor xid = 1 : s1
      for yid = 1 : s2
         output = struct;
         output.t = squeeze(temp(xid,yid,:));
         if ~isnan(temp(xid,yid,37))
            output.t(:) = 1;
         else
            output.t(:) = nan;
         end
         temp(xid,yid,:) = output.t;
      end
   end
end

In this case, I got the error message...

"Error using pwp_parallel (line 238) Error: The variable temp in a parfor cannot be classified.See Parallel for Loops in MATLAB, "Overview"."

However, if my code is looking like this...

fid = 'test.nc';
temp = ncread(fid,'temp');
[s1,s2,s3] = size(temp);

for m = 1 : 100
   parfor xid = 1 : s1
      for yid = 1 : s2
         output = struct;
         output.t = squeeze(temp(xid,yid,:));
         output.t(:) = 1;
         temp(xid,yid,:) = output.t;
      end
   end
end

The code is running.
Could someone help me to deal with this error?

Franke Hsu Franke Hsu · Accepted Answer · 2016-10-28T19:52:08

I figured it out by myself after I posted it lol

The question now is the if condition within the parfor doesn't recognize what the variable temp is. However, the if condition does recognize the variable output.t.

So, in this case, I just need to replace the variable "temp(xid,yid,37)" in the if condition by "output.t(37)", then the question is solved.

matlab parallel computing : the variable in a parfor is not classified

1 Answers