Many real world data, particularly in the natural sciences and computer vision, lie on known Riemannian manifolds such as spheres, tori or the group of rotation matrices. The predominant approaches to learning a distribution on such a manifold require solving a differential equation in order to sample from the model and evaluate densities. The resulting sampling times are slowed down by a high number of function evaluations. In this work, we propose an alternative approach which only requires a single function evaluation followed by a projection to the manifold. Training is achieved by an adaptation of the recently proposed free-form flow framework to Riemannian manifolds. The central idea is to estimate the gradient of the negative log-likelihood via a trace evaluated in the tangent space. We evaluate our method on various manifolds, and find significantly faster inference at competitive performance compared to previous work. We make our code public at https://github.com/vislearn/FFF.

我们提出了一种在Riemannian流形上进行分布学习的替代方法，该方法只需要一次函数评估，然后将结果投影到流形上。通过在切空间中评估的迹来估计负对数似然的梯度，我们在各种流形上评估了我们的方法，并发现相比之前的工作，推断速度显著提高且具有竞争性的性能。我们在该网址上公开了我们的代码。

使用自由形式流形学习流分布