OptimizationTechniques/Work2/scripts/gamma_armijo.m

function [gamma] = gamma_armijo(f, grad_f, x0)
    % Calculates the best step based on amijo method
    %
    % f(xk​− γk*∇f(xk)) ≤ f(xk) − σ*γk*∥∇f(xk)∥^2
    %
    % f:        Objective function
    % x0:       Initial (x,y) point
    
    
    % beta:     beta factor in (0, 1)
    % signam:   sigma factor in (0,1)
    global amijo_beta
    global amijo_sigma

    gamma = 1; % Start with a step size of 1

    grad = grad_f(x0(1), x0(2));

    % Perform Armijo line search
    while f(x0(1) - gamma * grad(1), x0(2) - gamma * grad(2)) > ...
          f(x0(1), x0(2)) - amijo_sigma * gamma * norm(grad)^2
        gamma = amijo_beta * gamma; % Reduce step size
    end

end