gradient_descent2 ( f(), fp(), x, r, dxtol, fptol, itmax  )

# gradient descent for a function of multiple parameters

  it = 0

  Loop1:

    if ||fp(x)|| < fptol ) return

    xold = x
    beta = 1.0
    Loop2:
      it = it + 1
      if ( itmax < it ) return
      dx = - beta * r * fp(xold)
      if ( ||dx|| < dxtol ) return
      x = xold + dx
      if f(x) < f(xold) break Loop2
      beta = beta / 2
    Loop2 end

  Loop1 end

  Return x

gradient_descent2 end