def _dsdt()

in gym/gym/envs/classic_control/acrobot.py [0:0]

• 30 lines of code
• 3 McCabe index (conditional complexity)

    def _dsdt(self, s_augmented, t):
        m1 = self.LINK_MASS_1
        m2 = self.LINK_MASS_2
        l1 = self.LINK_LENGTH_1
        lc1 = self.LINK_COM_POS_1
        lc2 = self.LINK_COM_POS_2
        I1 = self.LINK_MOI
        I2 = self.LINK_MOI
        g = 9.8
        a = s_augmented[-1]
        s = s_augmented[:-1]
        theta1 = s[0]
        theta2 = s[1]
        dtheta1 = s[2]
        dtheta2 = s[3]
        d1 = m1 * lc1 ** 2 + m2 * \
            (l1 ** 2 + lc2 ** 2 + 2 * l1 * lc2 * np.cos(theta2)) + I1 + I2
        d2 = m2 * (lc2 ** 2 + l1 * lc2 * np.cos(theta2)) + I2
        phi2 = m2 * lc2 * g * np.cos(theta1 + theta2 - np.pi / 2.)
        phi1 = - m2 * l1 * lc2 * dtheta2 ** 2 * np.sin(theta2) \
               - 2 * m2 * l1 * lc2 * dtheta2 * dtheta1 * np.sin(theta2)  \
            + (m1 * lc1 + m2 * l1) * g * np.cos(theta1 - np.pi / 2) + phi2
        if self.book_or_nips == "nips":
            # the following line is consistent with the description in the
            # paper
            ddtheta2 = (a + d2 / d1 * phi1 - phi2) / \
                (m2 * lc2 ** 2 + I2 - d2 ** 2 / d1)
        else:
            # the following line is consistent with the java implementation and the
            # book
            ddtheta2 = (a + d2 / d1 * phi1 - m2 * l1 * lc2 * dtheta1 ** 2 * np.sin(theta2) - phi2) \
                / (m2 * lc2 ** 2 + I2 - d2 ** 2 / d1)
        ddtheta1 = -(d2 * ddtheta2 + phi1) / d1
        return (dtheta1, dtheta2, ddtheta1, ddtheta2, 0.)