Converting FOR to PARFOR Code

Hello!

I am a bit confused about why I am having a particular error while converting a small and simple piece of my code form a FOR LOOP to a PARFOR LOOP. If someone could help me understand what I am missing I would be very thankful:

The original code is:

close all; clear all; clc;

slots = 3;
OutputV = '';
for j=1:2^slots
    if rand < 0.5
       strng = '0';
    else
       strng = '1';
    end
    OutputV = strcat(OutputV,strng);
end

OutputV = fliplr(OutputV);

Av = sym('a',[1,2^slots]);   % We require 2^slots variables
Eq = sym('eq',[1,2^slots]);  % We require 2^slots equations     
for ctr = 0:2^slots-1
    ctr
    S = dec2bin(ctr,4);
    S = fliplr(S); % Matlab reads from left to right so flip.

      A = strfind(S,'1');
      N = numel(A);
      L = length(S);
      Eq(1+ctr) = 0;

      for j=1:N
          B = combnk(A,j);
          coeff = sum(2.^(B-1),2);
          for k=1:numel(coeff)
              Eq(1+ctr) = Eq(1+ctr) + Av(1,coeff(k)+1); 
          end
      end
      % Need to substract constant term & output value
      Eq(1+ctr) = Eq(1+ctr) - Av(1,1) - OutputV(1+ctr);
  end

The modified code is:

    close all; clear all; clc;

slots = 5;

OutputV = '';
for j=1:2^slots
    if rand < 0.5
       strng = '0';
    else
       strng = '1';
    end
    OutputV = strcat(OutputV,strng);
end

OutputV = fliplr(OutputV);

Av = sym('a',[1,2^slots]);   % We require 2^slots variables
Eq = sym('eq',[1,2^slots]);  % We require 2^slots equations     

% Conver to parfor

parfor ctr = 0:2^slots-1
       S{1+ctr} = dec2bin(ctr,4);
       S{1+ctr} = fliplr(S{1+ctr});

         A{1+ctr} = strfind(S{1+ctr},'1');
         N{1+ctr} = numel(A{1+ctr});
         L{1+ctr} = length(S{1+ctr});

         Eq{1+ctr} = 0;

         for j = 1:N{1+ctr}
             B{1+ctr} = combnk(A{1+ctr},j);           % < --- Error here or
             coeff{1+ctr} = sum(2.^(B{1+ctr}-1),2);   % < --- Error here?
  %          for k=1:numel(coeff{1+ctr})
  %              Eq{1+ctr} = Eq{1+ctr} + Av(1,coeff(k)+1); 
  %          end
         end
         %  Need to substract constant term & output value
         %     Eq(1+ctr) = Eq(1+ctr) - Av(1,1) - OutputV(1+ctr);
  end

The error I get is: Error using LinearP3Parallel1>(parfor supply) An UndefinedFunction error was thrown on the workers for 'B'. This might be because the file containing 'B' is not accessible on the workers. Use addAttachedFiles(pool, files) to specify the required files to be attached. See the documentation for 'parallel.Pool/addAttachedFiles' for more details. Error in LinearP3Parallel1 (line 22) parfor ctr = 0:2^slots-1 Caused by: Undefined function 'B' for input arguments of type 'double'

Answer 1

[Walter Roberson]

Initialize B as a cell array of appropriate size before the parfor.

Someone else came across the same problem about a week ago.

[dsmalenb]

Thank you. I knew it was something stupid.