rivative
              ## 		        0 - one-sided derivative computed automatically
              ## 		        1 - one-sided derivative (f(x+h) - f(x)  )/h
              ## 		       -1 - one-sided derivative (f(x)   - f(x-h))/h
              ## 		        2 - two-sided derivative (f(x+h) - f(x-h))/(2*h)
              ## 			3 - user-computed analytical derivatives
              ## 
  deriv_debug*: cint ## Derivative debug mode: 1 = Yes; 0 = No;
                     ## 
                     ##                 