# Tag Info

14

Dropout essentially introduces a bit more variance. In supervised learning settings, this indeed often helps to reduce overfitting (although I believe there dropout is also already becoming less.. fashionable in recent years than in the few years before that; I'm not 100% sure though, it's not my primary area of expertise). In Reinforcement Learning, ...

8

Dropout means that every individual data point is only used to fit a random subset of the neurons. This is done to make the neural network more like an ensemble model. That is, just as a random forest is averaging together the results of many individual decision trees, you can see a neural network trained using dropout as averaging together the results of ...

7

Neural Networks have other short comings as well. It takes much longer and far more resources to train a neural network than something like a random forest. So if you need speed of training or are resource constrained in anyway, you probably should not look at Neural Networks first. Evaluation of a trained deep NN can be much more expensive than competing ...

7

In some iterative learning methods the more iterations you apply the more specific your model becomes about the training set. If there are too many iterations, your model will become too specifically trained for the training samples and will score less on other samples that are not seen during the training phase. This is call over-fitting, though over-...

6

The auto-encoder (AE) can be used to learn a compressed representation (a vectorised hash value) of each observation in the training dataset, $z$, which can then be used to later retrieve the original (or similar) observation. The variational auto-encoder (VAE), a statistical variation of AE, can also be used to generate objects similar to the observations (...

6

Typically the ramification of overfitting is poor performance on unseen data. If you're confident that overfitting on your dataset will not cause problems for situations not described by the dataset, or the dataset contains every possible scenario then overfitting may be good for the performance of the NN.

6

Generalization error is the error obtained by applying a model to data it has not seen before. So, if you want to measure generalization error, you need to remove a subset from your data and don't train your model on it. After training, you verify your model accuracy (or other performance measures) on the subset you have removed since your model hasn't seen ...

6

The original paper1 that proposed neural network dropout is titled: Dropout: A simple way to prevent neural networks from overfitting. That tittle pretty much explains in one sentence what Dropout does. Dropout works by randomly selecting and removing neurons in a neural network during the training phase. Note that dropout is not applied during testing and ...

6

First of all, as mentioned by @Neil Slater in the comment - you need to have three splits into the train, validation and test set. One sometimes disregards the difference between validation and test set. However they serve for different purposes. Here I would like to cite https://machinelearningmastery.com/difference-test-validation-datasets/ : Validation ...

5

Usually you keep track of training loss and validation loss and apply proper regularization technique (such as L1, L2, dropout, DropConnect, etc.). The more interesting technique is to observe your validation loss with respect to the number of parameters in the network (often controlled by the number of layers/feature maps). If the validation starts ...

5

Just to add to what has been said in @MikeWise's brilliant answer, All things equal, deep learning models generally rank supreme when compared to other algorithms as the size of the dataset increases: Like everything, it all boils down to the dataset at hand, neural networks are good on other datasets but at the same time, they will be bad on other ...

5

tl;dr The safest method I've found is to use cross-validation for hyperparameter selection and a hold-out test set for a final evaluation. Why this isn't working for you... In your case, I suspect you're either running a large number of iterations during for hyperparameter selection or you have a fairly small dataset (or even a combination of both). If you ...

5

Your reasoning isn't wrong. Deep Neural Networks (DNNs) have a much larger capacity than simpler ML algorithms (excluding NNs) and can easily memorize even a very complex dataset and overfit. DNNs, however, are so effective because they usually are applied on tasks that are harder, so it's not as easy to overfit. For example an image classifier might be ...

4

Regularization is one of the important prerequisites for improving the reliability, speed, and accuracy of convergence, but it is not a solution to every problem. Irregularity in data is only one of many root causes for slow or otherwise inadequate learning results, and as the results in the question indicates, it can reduce reliability, speed, or accuracy ...

4

Yes. Usually you would use cross validation to avoid overfitting during parameter tuning. If your dataset is large enough, and you don't try too many parameter combinations, this will work well, because to "get lucky" and overfit, a parameter combination will need to work very well on many variations of the problem, which is less likely than working well on ...

4

K-fold cross-validation is probably preferred in terms of completeness and generalization: you ensure that the system has seen the complete dataset for training. However, in deep learning this is often not feasible due to time and power constraints. They can both be used, and there is not one better than the other. It really depends on the specific case, the ...

3

Both of the solutions you suggest seem to be built around the intuition that it's good to ensure that there is sufficient variety in the experiences that you provide to your RL algorithm. That intuition is good, but it should not come at (too much of) a cost in playing strength of the opponent. I'm afraid that your first solution may break down because of ...

3

Is overfitting always a bad thing? The answer is a resounding yes, every time. The reason being that overfitting is the name we use to refer to a situation where your model did very well on the training data but when you showed it the dataset that really matter(i.e the test data or put it into production), it performed very bad. This can never be good, ...

3

How can data augmentation reduce overfitting? You write that you can already maybe see how data augmentation can help prevent overfitting in general, but it sounds a bit uncertain and it's still asked in the title of the question, so I'll address this first: Generally, when we use Machine Learning for classification problems, we would ideally learn a ...

3

There are some great answers here. The simplest explanation I can give for dropout is that it randomly excludes some neurons and their connections from the network, while training, to stop neurons from "co-adapting" too much. It has the effect of making each neuron apply more generally and is excellent for stopping overfitting for large neural networks.

3

Purely in terms of overfitting, and assuming you train both for equal amounts of time, 70/30 is probably better but performance is not going to be very good. Not training on %30 of data will make both training and test results equally bad (in my opinion). But it won't overfit, that is for sure. Cross validation (you have in mind 90/10, I assume) will take a ...

3

When ever you are buliding a ML Model don't take accuracy seriously(Mistake done by Netflix that cost them alot), you should try to get the hit scores as they will help you to know how many times your model worked on real world users.However, if your model must have to measure the accuracy try it with the RMSE score as it will penalise you more for being ...

3

There are a few issues you need to address first. Normalise your data. You should try and keep your values for each input in a good range, otherwise you're never going to train anything useful. A simple way of doing this could be to divide each value by the maximum value for that input. This will ensure they are between 0 and 1, or you could divide by the ...

3

Essentially, any data you use to train or develop the model shouldn't be used as test data. In principle, "unseen" data gives a good estimate for the generalisation performance of the model; but this is only valid if the data really is unseen and hasn't been used in the model development process. If you've been tuning a model to increase its ...

2

I'll try to answer your questions using Geoffrey Hinton's ideas in dropout paper and his Coursera class. What purpose does the "dropout" method serve? Deep neural nets with a large number of parameters are very powerful machine learning systems. However, overfitting is a serious problem in such networks. Large networks are also slow to use, making ...

2

Additional features can also cause overfitting if they have low or misleading information. Consider the following problem: $X = [1, 3, 3, 4, 5]$, $Y = [1, 3, 4, 4, 5]$. Suppose that the real dataset was generated from the relationship: $Y = X$, with a probability of 0.2 of adding or subtracting 1. A reasonable model estimate is $Y = X$. Note that no ...

2

The Problem of Overfitting In most cases, when you increase a lot the number of epochs your model finally overfits. This is because your model reaches the point that it does not learn anymore but tries to remember what it has seen before. This is overfitting. So there is often a trade-off between the number of epochs and overfitting. In general a good way to ...

2

It might be that your dataset of images is to small. Your discriminative network might hardlearn these images at which point your generative network can only produce good images if it copies the same images of your dataset.

2

Yes this looks a lot like overfitting. The clue is in the low and slowly decreasing training loss compared to the large increases in validation loss. One simple fix would be to stop training around epoch 50, taking the best cross validation result to select the most general network at that point. However, anything that works to improve stable generalisation ...

2

Overfitting refers to a model being stuck in a local minimum while trying to minimise a loss function. In Reinforcement Learning the aim is to learn an optimal policy by maximising (not always but almost) a reward function rather than minimising a loss function, so you can't really talk of overfitting as in the supervised scenario, but you can definitely ...

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