What does one validate that a trained NN has learned a correct method?
The Neural Net Tank Urban Legend
51–60 of 67 posts
Re: The Neural Net Tank Urban Legend
#52The whole "Could it happen"? section is a bit strange. On the one hand, it focuses on CNNs when it's clear we're talking about a binary classifier (the article itself points that out). If Fredkin was really the originator of the story, then discussing CNNs is an anachronism (they were 30 years away at the time). More importantly, it's obvious that "it" could definitely happen and in fact happens a lot- "it" being ove…
> One way or another, overfitting is no joke and it's definitely no urban legend. Can you give an example of where overfitting happened and was successfully corrected for?
That's why testing and validation sets exists. Overfitting is prevented by ending learning process when error on validation set starts growing. It is a standard procedure, so it's unlikely there's a recent case of overfitting slipping into production.
If irrelevant feature is present in all class samples, then it is not a fault of NN to use it as a class feature, it's bad data.
Re: The Neural Net Tank Urban Legend
#53Earlier quoted context omitted.
> One way or another, overfitting is no joke and it's definitely no urban legend. Can you give an example of where overfitting happened and was successfully corrected for?
That's why testing and validation sets exists. Overfitting is prevented by ending learning process when error on validation set starts growing. It is a standard procedure, so it's unlikely there's a recent case of overfitting slipping into production. If irrelevant feature is present in all class samples, then it is not a fault of NN to use it as a class feature, it's bad data.
So you would agree overfitting is not a real issue and talking about it is distracting from NN?
My question is are people using overfitting as an excuse of a what is instead a badly made NN.
If you are smart enough to create a NN that can tell if it's sunny or not then tanks would also be possible. But if your NN just sucks than blaming overfitting is a convenient out.
Re: The Neural Net Tank Urban Legend
#54Why is it called an urban legend, it seems to accurately depict how NNs work.
Re: The Neural Net Tank Urban Legend
#55> a common preprocessing step in computer vision (and NNs in general) is to whiten the image by standardizing or transforming pixels to a normal distribution; this would tend to wipe global brightness levels, promoting invariance to illumination Is there anybody still doing this?
No, it's not widely used anymore, although I wouldn't call it rare either. The most popular image CNNs don't use them: ResNets, Inception, VGG, fully convolutional nets, etc.
The Google query gwern cites is highly misleading because "normalize" in the context of neural nets for computer vision almost always means "subtract the average and then divide by the standard deviation."
Re: The Neural Net Tank Urban Legend
#56> a common preprocessing step in computer vision (and NNs in general) is to whiten the image by standardizing or transforming pixels to a normal distribution; this would tend to wipe global brightness levels, promoting invariance to illumination Is there anybody still doing this?
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Re: The Neural Net Tank Urban Legend
#57I've always liked this story better, it's in a somewhat similar vein: https://www.damninteresting.com/on-the-origin-of-circuits/
Re: The Neural Net Tank Urban Legend
#58I first encountered this idea in a sci-fi story (I want to say it was one of Peter Watts' "Rifters" novels, but I can't find it now). The idea was that someone trained a neural network to look at live video feeds of passengers moving through a subway station, and control the station's ventilation system. Unfortunately, the movements of individual people were fairly random, whereas the large-scale traffic patterns wer…
I thought i had a bleak outlook on life, until i started reading Watts novels and blog.
BTW, did he stop releasing his writing as creative commons?
Re: The Neural Net Tank Urban Legend
#59Makes me think of the story of soviet soldiers training dogs to carry explosives under tanks during WW2. Only they used their own tanks to train the dogs. So when deployed to the battlefield, well...
Re: The Neural Net Tank Urban Legend
#60Earlier quoted context omitted.
But ensuring correct datasets is a problem that people new to machine learning have to be made aware of. It's easy for people to see that NNs are good with 'noisy' data and incorrectly assume they can throw any data at it and get good results. And I think the quote is a false dilemma -- its not like we can't have multiple different stories for different problems. Make up / find a "truthy" story to spread for misoptim…
If a failure mode has never been reported in the wild, why is it so important to tell a juicy story about it, at the expense of attention to empirically observed failure modes?
Google's image tech confusing black people and gorillas?