to run than doing the actual filtering because well maxing you can run gradient descendant maybe at least find the local maximum whereas if you need to do an integration it kind of to sum over everything in the space and can be less tractable very often now one special case is the common filter or the linear Gaussian setting so summations become integral sure can't enumerate the overall associations but we can find solutions efficiently we know that when we have because we have multivariate gaussians everywhere the the crazy thing