contrastive.py 文件源码

def backward(self, inputs, gy):
        xp = cuda.get_array_module(*inputs)
        x0, x1, y = inputs

        x_dim = x0.shape[1]
        y = xp.repeat(y[:, None], x_dim, axis=1)
        alpha = gy[0] / y.shape[0]
        dist = xp.repeat(self.dist[:, None], x_dim, axis=1)
        # similar pair
        gx0 = alpha * y * self.diff
        # dissimilar pair
        mdist = xp.repeat(self.mdist[:, None], x_dim, axis=1)
        mdist_p = xp.array(mdist > 0, dtype=xp.int32)
        gx0 += alpha * (1 - y) * mdist_p * mdist * -(self.diff / dist)
        gx0 = gx0.astype(xp.float32)

        return gx0, -gx0, None