How to make this loop faster?

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Oliver Lestrange 2020-12-27

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评论： Jesús Zambrano 2020-12-28

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Hello,

The following code takes 30 seconds to execute. I can't make it any faster.

Any suggestion?

Thanks!

function [ at] = obstacleAttenuation( Ant, Movel, Obstaculo,mapa )
    tic
    fprintf('\nInside obstacleAttenuation function!\n');
    at = zeros(mapa.xlength, mapa.ylength);
    for xi=1:mapa.xlength
        for yi=1:mapa.ylength
            att = 0;
            [x, y] = bresenham(Ant.Antena_x, Ant.Antena_y, Movel.x(xi), Movel.y(yi));
            for i = 1:length(x)
                Obs = Obstaculo(x(i), y(i));
                att = att + Obs;
            end
            at(xi, yi) = att; 
%             Obs = Obstaculo(x(1:length(x)), y(1:length(x)));
%             att = sum(sum(Obs));
%             at(xi, yi) = att;
        end
    end
    
 fprintf('\nExit obstacleAttenuation function!\n');
 toc
end

NOTE: I am using R2016a version.

回答（1 个）

Jesús Zambrano 2020-12-27

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Is it possible to enter vectors as arguments in the function Obstaculo and get a vector as result? If so, then you could try replacing:

for i = 1:length(x)
    Obs = Obstaculo(x(i), y(i));
    att = att + Obs;
end

By:

i=1:length(x);
att = sum(Obstaculo(x(i), y(i)));

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Oliver Lestrange 2020-12-28

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Actually don't...

The difference between the two variables it's expected.

"at" gets 887x897 because it's the size of the image. Obstaculo gets the same dimension of the image because represents the obstacles of the map (image). Obstaculo function has the attenuation of each position of the map.

When I do

i=1:length(x);
att = sum(Obstaculo(x(i), y(i)));

I get a row vector like you said, and not a number.

But then, I should keep the attenuation in each part of the map.

In the following code, "att" gets just a number, not a row vector. I need that in order of at(xi, yi) = att; be possible. Because "att" is the sum of the obstacles on each path, and "Obstaculo" has the number of the attenuation in each part of the map. x and y are the path.

So, at the end of this function I need to have all the attenuations considering that bresenham each is a path.

function [ at] = obstacleAttenuation( Ant, Movel, Obstaculo,mapa )
    at = zeros(mapa.xlength, mapa.ylength);
    for xi=1:mapa.xlength
        for yi=1:mapa.ylength
            att = 0;
            [x, y] = bresenham(Ant.Antena_x, Ant.Antena_y, Movel.x(xi), Movel.y(yi));
            for i = 1:length(x)
                Obs = Obstaculo(x(i), y(i));
                att = att + Obs;
            end
            at(xi, yi) = att; 
        end
    end
end