# How to get this while cycle?

4 views (last 30 days)
Elia Paini on 16 Aug 2021
Commented: Elia Paini on 16 Aug 2021
Hi, I'm trying to get a while cycle which checks convergence every iteration.
Within the cycle, I'm solving a system which returns each iteration 3 types of solutions: a (vector), B, C (matrices).
Subscript "0" is related to the (l-1) iteraton, the other refers to the (l) iteration.
I wrote this code:
while (abs(a_0-a) > 1e-6) & (abs(B_0-B) > 1e-6) & (abs(C_0-C) > 1e-6)
....
end
It starts, but it do only one iteration, I don't know why.
It should iterate until ALL residues are lower than 1e-6.
Probably it's wrong, maybe due to parentheses or logical operators. I've already tried to change them, but in the other cases it doesn't work.
What should I do?

Fabio Freschi on 16 Aug 2021
if B and C are matrices, make them vectors using :
while any(abs(a_0-a) > 1e-6) || any(abs(B_0(:)-B(:)) > 1e-6) || any(abs(C_0(:)-C(:)) > 1e-6)
Elia Paini on 16 Aug 2021
Great, it works! Thank you!

Walter Roberson on 16 Aug 2021
while (abs(a_0-a) > 1e-6) || (abs(B_0-B) > 1e-6) || (abs(C_0-C) > 1e-6)
Elia Paini on 16 Aug 2021
I checked, the couples have the same dimension and orientation.
a_0 and a are (4x1), B_0 and B are (4x2), C_0 and C are (4x3)