problem with parfor variable

Hello,

i have a large code. I am summarizing the problem using a simple code.

parfor it=1:30
  for jt=1:30
    a(it,jt)=some_value;
  end
end

an error is shown."The variable a in a parfor cannot be classified." why cant matlab classify the variable? why does the variable 'a' fail to become a sliced variable?

Is there any other indexing scheme that can serve my purpose in the above mentioned code?

THANKS IN ADVANCE.

-OBLI

Answer 1

[Thomas]

the above code in its simple form works: just preallocate for speed

 a=zeros(30,30);    % preallocate variable a
 parfor it=1:30
  for jt=1:30
  a(it,jt)=rand(1);
  end
  end

the error in slicing the variable might come in from the part you probably left out..

[oblivious]

Have you checked your code? It does not run as well. The variable 'a' is not classified in your code too.

[Thomas]

It runs just fine for me.. with and without the matlabpool open..

running locally as well as on a cluster...

so apparently your pool is not set up right..

[Walter Roberson]

Thomas and oblivious: which MATLAB versions are you using? Different versions might diagnose differently.

[oblivious]

im using 7.10.0(R2010a)

[Thomas]

I have tested on 2011a,b,12 a.. Though the way matlabpool classifies variables was probably changed form 2011a.. and might be an issue in older ones..

[Thomas]

I believe if you make the parfor the inner most loop it might work in older versions..

for it=1:30

parfor jt=1:30

a(it,jt)=rand(1);

end

end

[oblivious]

Thanks Thomas

[Thomas]

is the problem with the sliced variable solved?

[oblivious]

nope, im trying it in another way

[Thomas]

I assume you are using Matlab older than R2011a..

[oblivious]

this problem was resolved in r2011a. i found in the release notes