字幕表 動画を再生する 英語字幕をプリント [MUSIC PLAYING] MAYA GUPTA: Hey, good morning. I'm Maya from Google AI. And I'm excited to share with you about TF Lattice. This is the same technology that we use at Google for many, dozens really, of our production models, where we care about the model behavior and we need to make sure that we can guarantee it's working sensibly everywhere. In particular, we're going to show how you can control your models to have monotonicity. So let me just dive into an example. An example I'm going to use here is a benchmark dataset from UCI, so you could play with this at home. And we have plenty of data here, 24,000 training examples. And there's more features in the dataset. We're just going to look at two, so that we can visualize what's happening. And what I'm showing here is the actual training data. So the two features are, are you single or are you married? And how many months has it been since you paid your bills? We're trying to solve the regression problem of predicting are you going to default on your credit. So what you can see is that while there's 24,000 samples, there's not that many people who haven't paid their bills for six months or more. So we're starting to get a bit sparse in that part of the region space. And what you're seeing here is the training data, in the mean and the confidence interval of the actual training data. So what happens when we go and train a model? Sort of visualize what's going to happen. Is a going to turn out to be important if you're single or married? Not really. It doesn't matter if you're single or married, it really matters how long it's been since you paid your bills. But the big surprise here is the model believes that it's better if you've not paid your bills for seven months than six months that you're going to get a higher credit score. So this is sad. This is bad AI behavior. And this is one of the reasons that some people don't like AI. And here we're just looking at this in a two-dimensional space. If we had the full 24 dimensional features or 30 or 100 features, there's going to be pockets of the space where this sort of thing may be happening and we may not even realize that we're getting this sort of bad, strange, possibly unethical behavior from our model. So what can we do? Well, we say, well, this is overfitting. Let's just regularize. But any of your standard regularization techniques are going to be problematic. It's going to be hard to really fix this without hurting your model accuracy. And it's going to be hard to even check if you really fixed it. So what the TF Lattice package does is it hits this problem exactly, and it lets you have monotonicity as a regularizer. You can say when you put together your features, for this feature it should only hurt my model, it should only hurt my score if I haven't paid my bills for a longer time. And so you can see here, this fixes that trend in the high number of months. And we get the same flexibility model. We actually get slightly better test accuracy, but we've solved the exact problem that we need to solve and we now have a guarantee on what the model is doing. And if we had 100 features, it would similarly guarantee that in all those pockets of 100 dimensional space, this was working correctly. So how does TF Lattice package do it? Well, under the hood, the kind of function class it's using are lattices, and these are just interpolated lookup tables. This is possibly the oldest way humanity has for representing function, right? You've seen these in the back of your math textbooks. You can find them in tables from actuary in 1960s, et cetera. So in a one-dimensional space, these are simply piecewise linear functions. But with the TF Lattice package, you can represent high dimensional functions also with these multidimensional lattices, multidimensional lookup tables. Here's an example with just two features. We're building a function with 10 lookup table parameter values there. And the lookup table parameter values are trained using empirical risk minimization. It's all the same training that you would see with DNN. It's just the parameters now represent what's happening with our function. And so it's much easier to control from monotonicity because there's a lot of structure to the function space. And with the TF Lattice package, you can kind of check and choose how much flexibility you want. So on the one extreme, you can just make a linear model. Very easy to make a linear model monotonic. You can generalized additive models, where you're using those 1D lattices. You can do these multidimensional lattice models. If you have a lot of features, you may want an ensemble of lattices. And we've set this up with layers, so you can mix and match and plug the players with other TF layers and create sort of cascade of deep lattice networks. Everything in the package it gives you smoothness. So compared to decision trees, you won't have this sort of piecewise constant behavior. You get smooth models and the monoticity guarantees that you select. And here's an example of five-layer deep lattice network where these squares are these 1D calibraters. And with the launch of TF 2.0, TF Lattice 2.0 will also be coming out in a month or two, and we'll support Keras layers as well. OK, so there's a GitHub link that you can get to. And there's a nice set of tutorials that walks through sort of all the complexity of what you might want to do. Also shows you how to like layer these things on top of DNNs for later layers, et cetera. The tutorials are sort of standalone. You can just work with them and figure out how to use this stuff. If you want to dig into the technical details, we have a series of papers. I'll just point you to this most recent paper and you can track back through some of the literature from that. All right, thank you very much. [APPLAUSE] [MUSIC PLAYING]
B1 中級 TFラティス。単調性でMLを制御する (TF Dev Summit '19) (TF Lattice: Control Your ML with Monotonicity (TF Dev Summit '19)) 1 0 林宜悉 に公開 2021 年 01 月 14 日 シェア シェア 保存 報告 動画の中の単語