a problem with implementing Gradient descent

Hi

I wrote the following programm implementation of gradient descent. But when I run the programm it works really slow . I guess it is because of the symbolic differentiation or maybe there is another problem in the implementaion . Can, you tell me what is wrong ?

function y = grad(x0,y0,z0,f,m1,m2)

syms a;

symsb;

symc c;

n=0;

if  (length(symvar(diff(f,a))==3)&& length(symvar(diff(f,b))==3) && length(symvar(diff(f,c))==3))

f_a = matlabFunction(diff(f,a),[a,b,c]);

f_b=matlabFunction(diff(f,b),[a,b,c]);

f_c=matlabFunction(diff(f,c),[a,b,c]);

else 

y= 0;    

return;

end

delta = -1*[f_a(x0,y0,z0), f_b(x0,y0,z0), f_c(x0,y0,z0)];

phi = @(t) ( f(x0+t*delta(1), y0+t*delta(2), z0+t*delta(3)) );

min = GRSMethod( phi,m1,m2 );

while ( abs ( min * ( delta(1)^2+delta(2)^2+delta(3)^2 ))> 10^ (-5) || n<100)

x0=x0+min*delta(1);

y0= y0+min*delta(2);

z0=z0+min*delta(3);

delta = -1*[f_a(x0,y0,z0), f_b(x0,y0,z0), f_c(x0,y0,z0)];

min = GRSMethod( phi,m1,m2 ); 

n=n+1;    
end 
y = [ x0,y0,z0];
end

Sincerely, Maria

[Walter Roberson]

Do not use "min" as the name of a variable: it interferes with using "min" as the name of the MATLAB and MuPAD routine.