Gradient

gradient

Parameters

step=real

(default: 0.000001)

cutoff=real

(default: -1.0)

Description

This function computes the gradient, i.e. the partial derivatives of the target function against the torsion angle, numerically and compares the result with the gradient computed by the (normal) analytic method. The numerical derivatives are calculated with the step size given by the step parameter, as well as by using a 10 times smaller and a 10 times larger step size. The deviation of the analytical gradient from the three numerically calculated gradient values are reported for all torsion angles for which the maximal absolute deviation exceeds the value set by the cutoff parameter.

This command is useful to check the analytical gradient calculation for correctness after a change of the target function and gradient calculation.