parfor loop variable cannot be classified

Hi all, I'm trying to use parfor instead of for to deal with 3 minimizations (for now, it should increase a lot) that are independent of each other in everything but the initial values. I have the data corresponding to each minimization in a different structure and the parameters over which I want to minimize, defined as scalars out of the structure. In particular, the code looks as follows (matlabpool is open before what follows).

p0=rand(3,1); % Initial guess for parameters, common to all %minimizations

for i=1:3,
    mk(i).param=zeros(3,1);
    mk(i).obj=zeros(1,1);
end
mk(1).mc=[2;3;4];
mk(2).mc=[1;3;2];
mk(3).mc=[2;4;1];

mk(1).n=6;
mk(2).n=8;
mk(3).n=15;

mk(1).id=1;
mk(2).id=2;
mk(3).id=3;

parfor i=1:3,
    [mk(i).param mk(i).obj]=fminsearch(@(p) prFOCv1(p,a;mk(i).mc,mk(i).n,mk(i).id),P0,Options);
end

So, every struct has components labeled mc, n and id and the values of each of these correspond to the values specified above and are independent of each other. If I use for instead of parfor, it works ok, but executes one minimization after the other, while I would like to do all simultaneusly. When I use parfor I get the message ???Error: The variable mk in a parfor cannot be classified. See Parallel for Loops in MATLAB, "Overview". I have read the "Overview" section, but I just don't understand what's the mistake that I'm making.

Any help would be appreciated. Thanks,

Fernando

Answer 1

[Walter Roberson]

Why is there a semi-colon in the call to prFOCv1 ?

Answer 2

[Fernando]

by mistake...but without the semi-colon I get the same error message.

I did a couple of changes to see what is causing the error. In particular, I decided to just evaluate the function prFOCv1 at the initial values, using parfor. This works OK.

parfor i=1:3,
    mk(i).obj=prFOCv1(p0,a,mk(i).mc,mk(i).n,mk(i).id);
end

So I guess that the problem is related to the way the output of the minimization is defined ( [mk(i).param mk(i).obj]=...).

[Walter Roberson]

You still have a semi-colon right after the "a" and before the "mk(i)" ??

[Fernando]

Sorry, that was a typo when writing the code (I didn't copy and paste). It is a , not a ;

[Walter Roberson]

You could try outputting to cell arrays indexed at "i", and put the structure back together afterwards.

[Fernando]

Great, that worked. Thanks.