the loop is not terminated it keeps on going

clear variables

close all

clc

A = [1 1 2; 1 2 4; 1 2 5];

x = [1; 2; 3];

Error = 0.000001;

Diff = ones(size(x));

iterCount = 0;

while Diff>Error

x1=(A*x);

Diff=norm(abs(x1-x));

x=x1./(x1(1,1));

iterCount = iterCount + 1;

end

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Answer 1

[Allen]

It is not clear why you initialize Diff as a vector whos size is equal to x. After you first compute Diff using the norm function, it becomes a scalar value whos size is a single element. Also, Diff converges to 18.6918 in about six iterations and will assume a value less than what you have defined by your Error variable. Assuming you are trying to determine when the difference of Diff between iterations is less than Error, try some similar to the following. Also, it is safe practice in while loops to add an additional break, such as a max number of iterations (included below) or a total lapsed duration exceeding a defined limit.

A = [1 1 2; 1 2 4; 1 2 5];
x = [1; 2; 3];
Diff = 1;
prevDiff = 0;
Error = 1e-6;
iterCount = 0;
maxIter = 1e5;
while iterCount<maxIter && abs(Diff-prevDiff)>Error
    x1 = (A*x);
    prevDiff = Diff;
    Diff = norm(abs(x1-x));
    x = x1./(x1(1,1));
    iterCount = iterCount+1;
end