svgd.py 文件源码

def svgd_kernel(self, theta, h = -1):
        sq_dist = pdist(theta)
        pairwise_dists = squareform(sq_dist)**2
        if h < 0: # if h < 0, using median trick
            h = np.median(pairwise_dists)  
            h = np.sqrt(0.5 * h / np.log(theta.shape[0]+1))

        # compute the rbf kernel
        Kxy = np.exp( -pairwise_dists / h**2 / 2)

        dxkxy = -np.matmul(Kxy, theta)
        sumkxy = np.sum(Kxy, axis=1)
        for i in range(theta.shape[1]):
            dxkxy[:, i] = dxkxy[:,i] + np.multiply(theta[:,i],sumkxy)
        dxkxy = dxkxy / (h**2)
        return (Kxy, dxkxy)