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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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Fotis Tsolakidis
Fotis Tsolakidis on 13 Jan 2021
Answered: SaiDileep Kola on 19 Jan 2021
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)

Answers (1)

SaiDileep Kola
SaiDileep Kola on 19 Jan 2021
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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