global variables - call function - parfor

Hi all,

I am trying to parallelize my code which basically solve odes with different boundary condition. The problem is that my equations need global variable which seems to be reset when calling a parfor loop. I use matlab R2014a and here is an example of code that (I think) should work :

Main program :

global a

a=8;
b=zeros(10,1);
parfor i=1:10
    b(i,1)=pluss(i);
end
b

function pluss :

function val=pluss(x)

global a
whos a
val=x+a;

It works fine with a for loop however with parfor the

who's a

gives as an answer

    Name      Size            Bytes  Class     Attributes

    a         0x0                 0  double    global

so the program stop running.

Does somebody has an idea how could I make this variable 'a' a 'real' global variable ?

thank you in advance,

Hugo P.

Answer 1

[Edric Ellis]

Global variables are not synchronized between the desktop MATLAB and the workers, as described in the documentation. You should aim to refactor your code to remove the need for globals. (Perhaps you could post a simple reproduction showing why you currently need to use globals).

Answer 2

[Hugo]

Hi,

Thank you for your answer. At the beginning of the code I calcul a huge matrix then use its coefficients in my differential equation. The problem is that calculate the matrix takes time however it will remain a constant during the for loop. This is why a global variable would be great...!

Any idea ? I was wondering if I can put more than t and y as parameter in my equation ?

Thank you,

Hugo

[Edric Ellis]

You can avoid transferring the data multiple times by taking advantage of the Worker Object Wrapper.

Answer 3

[Hugo]

Yeah it works, I can put my matrix as a variable of my ode.

thank you,