How to arrange correctly with a loop

Hello,

I have created a matrix and need to get a result of a vector using by the Gauss Diesel method.

This gives me an error because of the large iterations. What did I do wrong here ..

Thanks for the helpers

x = zeros(1,4^2);
x_new=x;   %x_new is the k+1 step
epsilon = 1e-3;
flag = 0;
counter = 0;

while flag == 0
    counter = counter + 1;
    if counter > 10000
        error('Too many iterations');
    end
end
f=4*ones(1,4^2);
m=diag(f);

j=0;
while j~=4^2
    [m(j+1,j+2)]=-1;
    [m(j+1,j+4)]=-1;
    [m(j+2,j+1)]=-1;
    [m(j+4,j+1)]=-1;
    j=j+1 ;
end
A=m(1:4^2,1:4^2);

b=zeros(1,4^2);
b(1)=1;
b(4^2)=1;

    for i = 1:4^2
        x_new(i) = (b(i) - sum(A(i,1:i-1).*x_new(1:i-1)) - sum(A(i,i+1:4^2).*x((i+1):4^2)))/A(i,i);
    end
    
    if max(abs(x_new-x)./abs(x_new)) < epsilon
        flag = 1;
    end
      
VectorOut=x_new';

Answer 1

[Walter Roberson]

The only thing you do in your while loop is increment the counter and test to see if it has become too large.

You need to extend your while loop to include more of the code.

j=0;
while j~=4^2
    [m(j+1,j+2)]=-1;
    [m(j+1,j+4)]=-1;
    [m(j+2,j+1)]=-1;
    [m(j+4,j+1)]=-1;
    j=j+1 ;
end

That looks like you programmed your code in C originally and converted it to MATLAB.

for j = 1 : 16
    m(j, j+1) = -1;
    m(j, j+3) = -1;
    m(j+1, j) = -1;
    m(j+3, j) = -1;
end

or

    j = 1 : 16;
    m(j, j+1) = -1;
    m(j, j+3) = -1;
    m(j+1, j) = -1;
    m(j+3, j) = -1;

[Emilia]

I did not understand can please show me a small example.

Does that mean my code here is not good?

j=0;
while j~=4^2
    [m(j+1,j+2)]=-1;
    [m(j+1,j+4)]=-1;
    [m(j+2,j+1)]=-1;
    [m(j+4,j+1)]=-1;
    j=j+1 ;
end

[Walter Roberson]

Either of the two sections I posted should work.

Your existing code for that section should work, but it is not well written.

The end you have just before

f=4*ones(1,4^2);

needs to be moved to the bottom of your code.

[Emilia]

I tried to make this code not work, returns an error.