parfor for double iteration??

Dear, I want to make a matrix G(m, n) as follows:

gamma = sqrt(sqrt(k/(E*I))); % gamma

G = zeros(length(x),length(qusi));

parfor n1 = 1:length(x)

    for n2 = 1:length(qusi)

        qua = gamma*abs(qusi(n2)-x(n1))/sqrt(2);

        G(n1,n2) = (gamma/(2*k))*exp(-qua)*sin(qua + pi/4);   % G(x,qusi)

    end

end

However, the error come up as follows:

Error using testsquare_test (line 53)

Error: The variable G in a parfor cannot be classified.

 See Parallel for Loops in MATLAB, "Overview".

I can't understand it. How should I do?

Could you please help me?

[Khoo]

Are you using the parallel computing from matlabpool? parfor is same as for-loop but it's in parallel computing.

Answer 1

[Edric Ellis]

Unfortunately, PARFOR doesn't understand how you're accessing 'G' even though you are using it in an order-independent way. What you need to do is build up a temporary row, and then assign it to the row of 'G' all in one go:

parfor n1 = 1:length(x)
  tempRow = zeros(1, length(qusi));
  for n2 = 1:length(qusi)
    qua = gamma*abs(qusi(n2)-x(n1))/sqrt(2);
    tempRow(n2) = (gamma/(2*k))*exp(-qua)*sin(qua + pi/4);
  end
  G(n1, :) = tempRow;
end

[Jinsoo]

Thank you very much.

Answer 2

[Madhura Suresh]

You will need to slice/classify your variables in parfor loops. Look at this blog:

http://blogs.mathworks.com/loren/2009/10/02/using-parfor-loops-getting-up-and-running/

[Jinsoo]

Thank you very much.