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Bayesian Neural Networks

cs.toronto.edu

21–30 of 60 posts

Re: Bayesian Neural Networks

#21

Author here! What a surprise. This was an abandoned project from 2019, that we never linked or advertised anywhere as far as I know. Anyways, happy to answer questions.

Somewhat related — I’d love to hear your thoughts on dex-Lang and Haskell for array programming?

Re: Bayesian Neural Networks

#22

Author here! What a surprise. This was an abandoned project from 2019, that we never linked or advertised anywhere as far as I know. Anyways, happy to answer questions.

why (if) was this not picked for further research? i know that oatml did quite amount of work on this front as well and it seems the direction is still being worked on. want to get ur 2 cent on this approach.

Re: Bayesian Neural Networks

#23

Bayesian Neural Networks just seem like a failed approach, unfortunately. For one, Bayesian inference and UQ fundamentally depends on the choice of the prior, but this is rarely discussed in the Bayesian NN literature and practice, and is further compounded by how fundamentally hard to interpret and choose these priors are (what is the intuition behind a NN's parameters?). Add to that the fact that the Bayesian infer…

> For one, Bayesian inference and UQ fundamentally depends on the choice of the prior, but this is rarely discussed in the Bayesian NN literature and practice, and is further compounded by how fundamentally hard to interpret and choose these priors are (what is the intuition behind a NN's parameters?).

I agree that, computationally, it is hard to justify the use of Bayesian methods on large-scale neural networks when stochastic gradient descent (and friends) is so damn efficient and effective.

On the other hand, the fact that there's a dependence on (subjective) priors is hardly a fair critique: non-Bayesian training of neural networks also depends on the use of (subjective) loss functions with (subjective) regularization terms (in fact, it can be shown that, mathematically, the use of priors is precisely equivalent to adding regularization to a loss function). Non-Bayesian training of neural networks is not "a failed approach" just because someone can arbitrarily choose L1 regularization (i.e., a Laplacian prior) over L2 regularization (i.e., a Gaussian prior).

Furthermore, we do have some intuition over NN parameters (particularly when inputs and outputs are properly scaled): a value of 10^15 should be less likely than a value of 0. Note that, in Bayesian practice, people often use weakly-informative priors (see, e.g., http://www.stat.columbia.edu/~gelman/presentations/weakprior...) to encode such intuitive statements while ensuring that (for all practical purposes) the data will effectively overwhelm the prior (again, this is equivalent to adding a minimal amount of regularization to a loss function, to make a problem well-posed when e.g. you have more parameters than data points).

Re: Bayesian Neural Networks

#24

Bayesian Neural Networks just seem like a failed approach, unfortunately. For one, Bayesian inference and UQ fundamentally depends on the choice of the prior, but this is rarely discussed in the Bayesian NN literature and practice, and is further compounded by how fundamentally hard to interpret and choose these priors are (what is the intuition behind a NN's parameters?). Add to that the fact that the Bayesian infer…

I’m not an expert in BNNs but the prior does not need to be justified in terms of each parameter. Bayesian analysis frequently uses hyperparameters to set the overall tightness or looseness of the parameters (a la Minnesota priors in the econometric literature for example). This would be a similar regularisation intuition as, eg, L1 and L2 regularisation in traditional NN training. This is of course just one example.

Re: Bayesian Neural Networks

#25

Bayesian Neural Networks just seem like a failed approach, unfortunately. For one, Bayesian inference and UQ fundamentally depends on the choice of the prior, but this is rarely discussed in the Bayesian NN literature and practice, and is further compounded by how fundamentally hard to interpret and choose these priors are (what is the intuition behind a NN's parameters?). Add to that the fact that the Bayesian infer…

I agree that Bayesian neural networks haven't been worth it in practice for many applications, but I think the main problem is that it's usually better to spend your compute training a single set of weights for a larger model, rather than doing approximate inference over weights in a smaller model. The exception is probably scientific applications where you mostly know the model, but then you don't really need a neur…

I disagree with one conceptual point; if you are truly Bayesian you don’t “choose” a prior, by definition you “already have” a prior that you are updating with data to get to a posterior.

Re: Bayesian Neural Networks

#26

Bayesian Neural Networks just seem like a failed approach, unfortunately. For one, Bayesian inference and UQ fundamentally depends on the choice of the prior, but this is rarely discussed in the Bayesian NN literature and practice, and is further compounded by how fundamentally hard to interpret and choose these priors are (what is the intuition behind a NN's parameters?). Add to that the fact that the Bayesian infer…

What is 'UQ', I assume some measure of uncertainty over your model outputs?

Re: Bayesian Neural Networks

#27
post #26

Bayesian Neural Networks just seem like a failed approach, unfortunately. For one, Bayesian inference and UQ fundamentally depends on the choice of the prior, but this is rarely discussed in the Bayesian NN literature and practice, and is further compounded by how fundamentally hard to interpret and choose these priors are (what is the intuition behind a NN's parameters?). Add to that the fact that the Bayesian infer…

What is 'UQ', I assume some measure of uncertainty over your model outputs?

Unbiased quantifier

Re: Bayesian Neural Networks

#28
post #25

Earlier quoted context omitted.

I agree that Bayesian neural networks haven't been worth it in practice for many applications, but I think the main problem is that it's usually better to spend your compute training a single set of weights for a larger model, rather than doing approximate inference over weights in a smaller model. The exception is probably scientific applications where you mostly know the model, but then you don't really need a neur…

I disagree with one conceptual point; if you are truly Bayesian you don’t “choose” a prior, by definition you “already have” a prior that you are updating with data to get to a posterior.

At some level, you have to choose something. You can't know every level in your hierarchy.

Re: Bayesian Neural Networks

#29
post #25

Earlier quoted context omitted.

I agree that Bayesian neural networks haven't been worth it in practice for many applications, but I think the main problem is that it's usually better to spend your compute training a single set of weights for a larger model, rather than doing approximate inference over weights in a smaller model. The exception is probably scientific applications where you mostly know the model, but then you don't really need a neur…

I disagree with one conceptual point; if you are truly Bayesian you don’t “choose” a prior, by definition you “already have” a prior that you are updating with data to get to a posterior.

100% correct, but there are ways to push Bayesian inference back a step to justify this sort of thing.

It of course makes the problem even more complex and likely requires further approximations to computing the posterior (or even the MAP solution).

This stretches the notion that you are still doing Bayesian reasoning but can still lead to useful insights.

Re: Bayesian Neural Networks

#30
post #29
post #25

Earlier quoted context omitted.

I disagree with one conceptual point; if you are truly Bayesian you don’t “choose” a prior, by definition you “already have” a prior that you are updating with data to get to a posterior.

100% correct, but there are ways to push Bayesian inference back a step to justify this sort of thing. It of course makes the problem even more complex and likely requires further approximations to computing the posterior (or even the MAP solution). This stretches the notion that you are still doing Bayesian reasoning but can still lead to useful insights.

Probably should just call it something else then; though, I gather that the simplicity of Bayes theorom belies the complexity of what it hides.
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