mmd.py 文件源码

def _mix_rbf_kernel(X, Y, sigmas, wts=None):
    if wts is None:
        wts = [1] * len(sigmas)

    XX = tf.matmul(X, X, transpose_b=True)
    XY = tf.matmul(X, Y, transpose_b=True)
    YY = tf.matmul(Y, Y, transpose_b=True)

    X_sqnorms = tf.diag_part(XX)
    Y_sqnorms = tf.diag_part(YY)

    r = lambda x: tf.expand_dims(x, 0)
    c = lambda x: tf.expand_dims(x, 1)

    K_XX, K_XY, K_YY = 0, 0, 0
    for sigma, wt in zip(sigmas, wts):
        gamma = 1 / (2 * sigma**2)
        K_XX += wt * tf.exp(-gamma * (-2 * XX + c(X_sqnorms) + r(X_sqnorms)))
        K_XY += wt * tf.exp(-gamma * (-2 * XY + c(X_sqnorms) + r(Y_sqnorms)))
        K_YY += wt * tf.exp(-gamma * (-2 * YY + c(Y_sqnorms) + r(Y_sqnorms)))

    return K_XX, K_XY, K_YY, tf.reduce_sum(wts)