How to vectorize the evaluation of a kernel function.

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Jingyu 2022-11-27

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1864753-how-to-vectorize-the-evaluation-of-a-kernel-function

评论： Jingyu 2022-12-5

采纳的回答： Matt J

在 MATLAB Online 中打开

I have a kernal function

which is defined for

. And now I have to compute a matrix

for m points

and n points

, where K is given by

. It is direct when using two for loop. But how can I vectorize the evaluation? For example, I tried

k_fun = @(x, y) 1 / norm(x - y);
d = 2;  % Make d = 1 if you want it runs correctly.
m = 100;
n = 100;
x_points = rand(m, d);
y_points = rand(n, d);
% The following code is the two for loop version.
K = zeros(m, n);
for i = 1 : m
    for j = 1 : n
        K(i, j) = k_fun(x_points(i,:), y_points(j, :));
    end
end
% The folloing code works when d = 1, but when d > 1 it failes.
K = k_fun(x_points, y_points');
% When d > 1, the error is "Arrays have incompatible sizes for this
% operation."

When

, it gives the result I want, But for

, it failes. How can I improve it?

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Jan 2022-12-5

@Jingyu: "I have told you the code will occur error" - yes, you did. Please insert the error message also in future questions.

While your code is vectorized already, you let the readers guess, what you want to achieve. All we know, is that your kernal function is "special" and the not working code.

Jingyu 2022-12-5