## While loop with for loop problem

Asked by José Everardo Baldo Junior

### José Everardo Baldo Junior (view profile)

on 19 Apr 2019
Latest activity Commented on by José Everardo Baldo Junior

on 23 Apr 2019

### Stephen Cobeldick (view profile)

Hello everyone!
I have a situation here trying to solve a while loop inside a for loop.
As you can see in the code, I want to calculate "xn", varying "omega" and then, evaluate which "omega" gives the minor number of iterations (nite), storing in a vector (nite_vec) the each "nite" for each "omega" used in the looping.
But the counte "i" does not to up date inside the "while".
%% Iterations
D = [3 0 0; 0 2 0; 0 0 1];
b = [0; 1; 0];
L = [0 0 0; 1 0 0; 0 1 0];
U = [0 1 0; 0 0 1; 0 0 0];
tol = 10^-7;
nite_max = 100;
n = length(b);
x0 = zeros(n,1);
omega = (1:0.05:2)';
nite = 0;
xn = 1;
xi = x0;
for i = 1:length(omega)
while norm(xn-xi) >= tol && nite <= nite_max
xn = (D-omega(i)*L)\((1-omega(i))*D+omega(i)*U)*x0+omega(i)*((D-omega(i)*L)\b);
xi = x0;
x0 = xn;
nite = nite+1;
end
nite_vec(i) = nite;
end
Could anyone help me with this!
Many thanks!

### Stephen Cobeldick (view profile)

on 19 Apr 2019
Edited by Stephen Cobeldick

### Stephen Cobeldick (view profile)

on 19 Apr 2019

Perhaps you meant something like this:
D = [3 0 0; 0 2 0; 0 0 1];
b = [0; 1; 0];
L = [0 0 0; 1 0 0; 0 1 0];
U = [0 1 0; 0 0 1; 0 0 0];
tol = 10^-7;
n = numel(b);
nite_max = 100;
omega = 1:0.05:2;
for k = 1:numel(omega)
nite = 0;
x0 = zeros(n,1);
xn = 1;
xi = x0;
while norm(xn-xi)>=tol && nite<=nite_max
xn = (D-omega(k)*L)\((1-omega(k))*D+omega(k)*U)*x0+omega(k)*((D-omega(k)*L)\b);
xi = x0;
x0 = xn;
nite = nite+1;
end
nite_vec(k) = nite;
end
Giving:
>> nite_vec
nite_vec = 41 36 32 28 24 19 16 17 20 22 25 29 34 40 48 58 75 101 101 101 101

#### 1 Comment

José Everardo Baldo Junior

### José Everardo Baldo Junior (view profile)

on 23 Apr 2019
Hello Stephen!
That's it! Many thankls for your help!!!
Kind regards,
Junior.