Using Arrays inside arrayfun()

Question

Maxime Rivard 2017-12-23

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https://ww2.mathworks.cn/matlabcentral/answers/374334-using-arrays-inside-arrayfun

回答： Joss Knight 2017-12-26

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.

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Answer 1

Matt J 2017-12-23

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https://ww2.mathworks.cn/matlabcentral/answers/374334-using-arrays-inside-arrayfun#answer_297527

编辑：Matt J 2017-12-23

在 MATLAB Online 中打开

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

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Maxime Rivard 2017-12-23

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

Matt J 2017-12-23

编辑：Matt J 2017-12-23

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.

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Answer 2

Walter Roberson 2017-12-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/374334-using-arrays-inside-arrayfun#answer_297530

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

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Walter Roberson 2017-12-23

在 MATLAB Online 中打开

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

Matt J 2017-12-24

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

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Answer 3

Joss Knight 2017-12-26

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https://ww2.mathworks.cn/matlabcentral/answers/374334-using-arrays-inside-arrayfun#answer_297758

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.