Transparency violation

Hi,

I have this code segment within a parfor ... end loop. Error flagged off, complaining about the way LT is used, so the code would not run.

% I have 8 workers

matlabpool open local 8

parfor n=1:100

.

. % other codes here

.
yt = UT + round ((Long(n)/15)*60);

      for i=1:1440

          if yt(i) <= 1440;
              LT(i) = yt(i);
              elseif yt(i) > 1440
              LT(i) = yt(i)-1440;
          end;
       end; 

.

. % other codes here too

.

end % parfor end

matlabpool close

I read some helpful note, transparency error and variable classification error were referred to, but could still not resolve the problem.

So, I may need to slice the variable LT or so. Kindly help to fix this code.

Felix

Answer 1

[Walter Roberson]

Perhaps use logical indexing?

yt = UT + round ((Long(n)/15)*60);
LT = yt;
LT(LT>1440) = LT(LT>1440)-1440;

Answer 2

[Edric Ellis]

You're not indexing 'LT' with the loop variable, so it can never be 'sliced'. Are you calculating the whole of 'LT' each time around your main PARFOR loop? If so, it might help to pre-allocate it so that PARFOR knows you're not trying to use it in an order-dependent way. Something like

parfor n = 1:100
  LT = zeros(1,1440);
  for i = 1:1440
     % do stuff
  end
end

[Facosoft]

I thank you. The solution provided would cause unnecessary communication overhead when dividing the work among the lab workers...Indexing is just not enough but would at least handle the error. Thanks