function [x,y,z] = minimumSearch(u)
global del g;
del = 10e-6;
tol = 10e-4;
delta = tol +1;
nmax = 10;
n = 0;
x = 0;
y = 0;
z = 0;
g = u;
    
fprintf('\n Iteration %d : error = %14.7e, objective = %14.7e ',n,max(abs(delta)),u(x,y,z))

while abs(norm(delta)) >= tol & n <= nmax
    n = n+1;
    delta = -f(x,y,z) / dfdx(x,y,z);
    x = x + delta(1);
    y = y + delta(2);
    z = z + delta(3);
    fprintf('\n Iteration %d : error = %14.7e, objective = %14.7e ',n,max(abs(delta)),u(x,y,z))
end
end


function f = f(x,y,z)
global del g;
gg = g(x,y,z);
f(1) = (g(x+del,y,z) - gg)/del; 
f(2) = (g(x,y+del,z) - gg)/del; 
f(3) = (g(x,y,z+del) - gg)/del; 
end      

function dfdx = dfdx(x,y,z)
global del g;
ff = f(x,y,z);
dfdx(1,:) = (f(x+del,y,z) - ff)/del; 
dfdx(2,:) = (f(x,y+del,z) - ff)/del; 
dfdx(3,:) = (f(x,y,z+del) - ff)/del; 
end