the script works normally for few data but if it accepts a table with a lot of data it takes too long time (>1hr........give a result but in a long time)

Question

Fotis Tsolakidis 2021-1-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/716443-the-script-works-normally-for-few-data-but-if-it-accepts-a-table-with-a-lot-of-data-it-takes-too-lon

回答： SaiDileep Kola 2021-1-19

the script works normally for few data but if it accepts a table with a lot of data it takes too long time (>1hr........give a result but in a long time)
clear;clc;close all;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
pref=input('Please enter file prefix: ','s');
    fn=[pref '.mhk'];
    fr=fopen(fn,'r');
    k=0;
error = false;
t = fgetl(fr);
XTH = [];
Yed = [];
while ~feof(fr)
    t = fgetl(fr);
    [temp,~]=sscanf(t,'%f');
    if ~error
        k = k + 1;
        XTH(k) = temp(1);
        Yed(k) = temp(2);
    end
end
x = [XTH(1)];
y = [Yed(1)];
XTH=[x XTH];
Yed = transpose([y Yed]);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
n = length(XTH); 
l = 0;
k = 0;
Vmin = 100000000;
r=0;
for u1 = 1:XTH(end) 
    l = l + 1;
    
    if ismember(u1,XTH)==1
        u1 = u1 + 0.1;
    end
        
    if u1>=XTH(1)+1 && u1< XTH(end)-1
        for u2 = u1:XTH(end)
            k = k + 1;
            
            if u2 == u1
               u2 = u2 + 1;
            end
            
            if ismember(u2,XTH)
               u2 = u2 + 1;
            end
   
            XTH = [(XTH) u1 u2];
            XTH = sort(XTH);
            num1 = find(XTH==u1);
            num2 = find(XTH==u2);
            XTH = XTH(XTH~=u1);
            XTH = XTH(XTH~=u2);
            a11 = XTH(1:num1);
            a12 = repelem(u1,length(XTH)-num1);
            a1 = transpose([a11, a12]); 
            a2 = ones(n,1);
            a31 = transpose(zeros(num1,1));
            a32 = XTH(num1+1:num2-1)-u1;
            a33 = repelem(u2-u1,length(XTH(num2:end)));
            a3 = transpose([a31 a32 a33]);
            a41 = transpose(zeros(num2-1,1));
            a42 = XTH(num2:end)-u2;
            a4 = transpose([a41 a42]);
            A = [a1 a2 a3 a4];
            AtA = transpose(A)*A;
            B = Yed;
            AtB = transpose(A)*B;
            if det(AtA)==0 
               continue 
            end
            if det(AtA)<1e-3
               continue
            end
            solution = linsolve(AtA, AtB);
            alpha1 = solution(1,1);
            beta1 = solution(2,1);
            alpha2 = solution(3,1);
            alpha3 = solution(4,1);
            beta2 = (alpha1*u1) + beta1 - (alpha2*u1);
            beta3 = (alpha1*u1) + beta1 + alpha2*(u2-u1) - (alpha3*u2);
            dy1 = 0;
            dy2 = 0;
            dy3 = 0;
            Dx = XTH(end)-XTH(1);
            width = 10;
            for j = 1:num1
                dy1 = dy1 + abs((Yed(j)-(alpha1*XTH(j)+beta1)));
            end
            for j = num1:num2-1
                dy2 = dy2 + abs((Yed(j) - (alpha2*XTH(j)+beta2)));
            end
            for j = num2:n
                dy3 = dy3 + abs((Yed(j) - (alpha2*XTH(j)+beta2)));
            end
             V(l+k) = Dx*width*(1/length(Yed))*(dy1+dy2+dy3);
             if V(l+k) < Vmin && V(l+k)~=0
                 aa1 = alpha1;
                 aa2 = alpha2;
                 aa3 = alpha3;
                 bb1 = beta1;
                 bb2 = beta2;
                 bb3 = beta3;
                 U1 = u1;
                 U2 = u2;
                 Vmin = V(l+k);
             end
        end
    end
end
bar(V(l+k),XTH)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
plot(transpose(XTH), Yed, 'k')
daspect([10,1,1]);
% ax = gca;
% ax.XLim = [XTH(1) XTH(end)];
hold on;
grid on;
x11 = XTH(1);
x21 = U1;
y11 = aa1*x11 + bb1;
y21 = aa1*x21 + bb1;
plot([x11,x21],[y11,y21], 'r')
x21 = U1;
x22 = U2;
y21 = aa2*x21 + bb2;
y22 = aa2*x22 + bb2;
plot([x21,x22],[y21,y22], 'r')
x31 = U2;
x32 = XTH(end);
y31 = aa3*x31 + bb3;
y32 = aa3*x32 + bb3;
plot([x31,x32],[y31,y32], 'r')
%line(U1,aa1*U1 + bb1)
disp('Line equation 1:')
line1 = ['y = ', num2str(aa1),'*x + ',num2str(bb1)];
disp(line1)
disp('Line equation 2:')
line2 = ['y = ', num2str(aa2),'*x + ',num2str(bb2)];
disp(line2)
line3 = ['y = ', num2str(aa3),'*x + ',num2str(bb3)];
disp(line3);
vol = [num2str(Vmin),' m^3'];
disp('Minimum volume achieved:')
disp(vol)

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Answer 1

SaiDileep Kola 2021-1-19

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/716443-the-script-works-normally-for-few-data-but-if-it-accepts-a-table-with-a-lot-of-data-it-takes-too-lon#answer_601169

Decent way to do is know which parts of the code are taking long time by profiling, check link for profile documentation here, then check for optimisation or alternative snippets for that part.

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the script works normally for few data but if it accepts a table with a lot of data it takes too long time (>1hr........give a result but in a long time)

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the script works normally for few data but if it accepts a table with a lot of data it takes too long time (>1hr........give a result but in a long time)

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