Using Arrays inside arrayfun()

I'm using gpuArrays with arrayfun to speed up calculations, and I would need to pass an array inside the call, as such

    [Zn] = arrayfun( @iterFuncDelta,Xo,Yo,orbit)

function [Zn] = iterFuncDelta(xdelta0,ydelta0,refOrbit)
maxIterations=2^15;
delta=complex(xdelta0,ydelta0);
delta0=delta;
n=2;
Zn=refOrbit(1,1)+delta;

while ( n <= maxIterations )
    Zn=refOrbit(n,1)+delta;
    delta=2*refOrbit(n,1)*delta+delta^2+delta0;
    n=n+1;
end
end

How could I pass the array 'orbit' so that it is not treated as a single point (like Xo and Yo) ?

Thanks.

Answer 1

[Matt J]

According to this example, it should be possible with a nested function. Not sure how fast it's likely to be, though.

function Outer(Xo,Yo,orbit) %EDIT

        refOrbit=orbit;

        function [Zn] = iterFuncDelta(xdelta0,ydelta0)

            maxIterations=2^15;
            delta=complex(xdelta0,ydelta0);
            delta0=delta;
            n=2;
            Zn=refOrbit(1,1)+delta;
            while ( n <= maxIterations )
                Zn=refOrbit(n,1)+delta;
                delta=2*refOrbit(n,1)*delta+delta^2+delta0;
                n=n+1;
            end
        end

        [Zn] = arrayfun( @iterFuncDelta,Xo,Yo);

 end

[Maxime Rivard]

But in that case, how does the arrayfun() call get access to the arrays Xo and Yo?

[Matt J]

You would pass that to Outer() as well (see edit). I of course can't know what other variables you actually have in your workspace, nor how they got there. The inclusion of Outer() was just an example to show the nested context needed for iterFuncDelta.

Answer 2

[Walter Roberson]

http://www.mathworks.com/help/matlab/math/parameterizing-functions.html

[Maxime Rivard]

This seems to be the other way around than what I need: your article explains how to have extra parameters from the parent function, but I need to have parameters coming from the nested function. From the previous response:

function Outer(orbit)
        refOrbit=orbit;
        function [Zn] = iterFuncDelta(xdelta0,ydelta0)
         [code]
        end
        [Zn] = arrayfun( @iterFuncDelta,Xo,Yo);
 end

Calling Outer(orbit) does not work (the arrayfun() call doesn't see Xo and Yo from the workspace). What am I doing wrong?

[Walter Roberson]

[Zn] = arrayfun( @(x,y) iterFuncDelta(x,y,orbit), Xo, Yo )

[Matt J]

I don't think this will work on the GPU.

Answer 3

[Joss Knight]

You can't do any array or matrix operations in a GPU arrayfun kernel. You can access the contents of an array that is present as an up-level variable such as has been demonstrated in the comments. You can then loop over the contents of the array one element at a time, to emulate array operations such as a dot product. This blog article gives an example of doing this for a simple 3-vector.