Question

这是我的matlab代码。它运行得太慢，我不知道如何改进它。

你能帮助我提高速度吗？

我想做的是创建一些随机点，然后移除随机点，使它们与我的目标点相似。

syms Dx Dy p q;

a = 0;

num = 10;
x = rand(1,num);
y = rand(1,num);
figure(1)
scatter(x,y,'.','g')

%num_x = xlsread('F:\bin\test_2');% num 1024
%figure(2)
%scatter(num_x(:,1),num_x(:,2),'.','r');

q = 0;
num_q = 10;

x_q = randn(1,num_q);
y_q = randn(1,num_q);

%figure(2)
hold on;
scatter(x_q,y_q,'.','r')

for i = 1:num_q;
    for j = 1:num_q;
        qx(i,j) = x_q(i) - x_q(j);
        qy(i,j) = y_q(i) - y_q(j);       
        %qx(i,j) = num_x(i,1) - num_x(j,1);
        %qy(i,j) = num_x(i,2) - num_x(j,2);
        %d~(s(i),s(j))
        if ((qx(i,j))^2+(qy(i,j)^2))> 0.01 % find neighbours
            qx(i,j) = 0;
            qy(i,j) = 0;
        end  
    end
end

for i = 1:num_q;
    for j = 1:num_q;
        if qx(i,j)>0&&qy(i,j)>0
        q = q + exp(-(((Dx - qx(i,j))^2)+((Dy - qy(i,j))^2))/4);%exp(-(((Dx - qx(i,j))^2)+((Dy - qy(i,j))^2))/4);
        end
    end
end

%I = ones(num,num); % I(s) should from a grayscale image
%r = 1./sqrt(I);
for s = 1:100;

for i = 1:num;
    for j = 1:num;
        dx(i,j) = x(i) - x(j);
        dy(i,j) = y(i) - y(j);
        %d~(s(i),s(j))
        if ((dx(i,j))^2+(dy(i,j)^2))> 0.05 % delta p, find neighbours
            dx(i,j) = 0;
            dy(i,j) = 0;
        end  
    end
end

p = 0;
for i = 1:num;
    for j = 1:num;
        if dx(i,j)>0&&dy(i,j)>0
        p = p + exp(-(((Dx - dx(i,j))^2)+((Dy - dy(i,j))^2))/4);
        end
    end
end

p = p - q;
sum = 0;
for i = 1:num;
    for j = 1:num;
        if dx(i,j)>0&&dy(i,j)>0;
        kx(i,j) = (1/2)*(Dx-dx(i,j))*exp((-(Dx-dx(i,j))^2+(Dy-dy(i,j))^2)/4);
        ky(i,j) = (1/2)*(Dy-dy(i,j))*exp((-(Dx-dx(i,j))^2+(Dy-dy(i,j))^2)/4);
        end
    end
end

sum_x = ones(1,num);% 1行N列0矩阵
sum_y = ones(1,num);

%fx = zeros(1,num);


for i = 1:num;
    for j = 1:num;
        if dx(i,j)>0&&dy(i,j)>0;
            fx(i) = p*kx(i,j);% j is neighbour to i
            fy(i) = p*ky(i,j);

            %fx(i) = matlabFunction(fx(i));
            %fy(i) = matlabFunction(fy(i));
            %P =quad2d(@(Dx,Dy) fx,0,0.01,0,0.01);
            %fx =quad(@(Dx) fx,0,0.01);
            %fx(i) =quad(@(Dy) fx(i),0,0.01);
            %Q =quad2d(@(Dx,Dy) fy,0,0.01,0,0.01);

            fx(i) = double(int(int(fx(i),Dx,0,0.01),Dy,0,0.01));
            fy(i) = double(int(int(fy(i),Dx,0,0.01),Dy,0,0.01));

            %fx(i) = vpa(p*kx(i,j));
            %fy(i) = vpa(p*ky(i,j));



            %fx(i) = dblquad(@(Dx,Dy)fx(i),0,0.01,0,0.01);
            %fy(i) = dblquad(@(Dx,Dy)fy(i),0,0.01,0,0.01);        
            sum_x(i) = sum_x(i) + fx(i);
            sum_y(i) = sum_y(i) + fy(i);
        end
    end
end

for i = 1:num;
sum_x = 4.*sum_x./num;
sum_y = 4.*sum_y./num;
x(i) = x(i) - 0.05*sum_x(i);
y(i) = y(i) - 0.05*sum_y(i);
end

a = a+1

end
hold on;
scatter(x,y,'.','b')

Answer 1

你的循环的快速版本应该是这样的：

qx = bsxfun(@minus, x_q.', x_q);
qy = bsxfun(@minus, y_q.', y_q);

il     = (qx.^2 + qy.^2 >= 0.01);
qx(il) = 0;
qy(il) = 0;

il  = qx>0 && qy>0;
q   = sum(exp(-((Dx-qx(il)).^2 + (Dy-qy(il)).^2)/4));

%// etc. for vectorization of the inner loops

如何提高matlab的速度

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