features.py 文件源码

def Kuu(self, kern, jitter=0.0):
        if isinstance(kern, kernels.RBF):
            with decors.params_as_tensors_for(kern):
                Zmu, Zlen = kern._slice(self.Z, self.scales)
                idlengthscales2 = tf.square(kern.lengthscales + Zlen)
                sc = tf.sqrt(
                    tf.expand_dims(idlengthscales2, 0) + tf.expand_dims(idlengthscales2, 1) - tf.square(
                        kern.lengthscales))
                d = self._cust_square_dist(Zmu, Zmu, sc)
                Kzz = kern.variance * tf.exp(-d / 2) * tf.reduce_prod(kern.lengthscales / sc, 2)
                Kzz += jitter * tf.eye(len(self), dtype=settings.float_type)
            return Kzz
        else:
            raise NotImplementedError(
                "Multiscale features not implemented for `%s`." % str(type(kern)))