kernels.py 文件源码

def K(self, X, X2=None, presliced=False):
        if not presliced:
            X, X2 = self._slice(X, X2)

        X_denominator = tf.sqrt(self._weighted_product(X))
        if X2 is None:
            X2 = X
            X2_denominator = X_denominator
        else:
            X2_denominator = tf.sqrt(self._weighted_product(X2))

        numerator = self._weighted_product(X, X2)
        cos_theta = numerator / X_denominator[:, None] / X2_denominator[None, :]
        jitter = 1e-15
        theta = tf.acos(jitter + (1 - 2 * jitter) * cos_theta)

        return self.variance * (1. / np.pi) * self._J(theta) * \
               X_denominator[:, None] ** self.order * \
               X2_denominator[None, :] ** self.order