  Estimating the relative importance of each sample in a training set has
important practical and theoretical value, such as in importance sampling or
curriculum learning. This kind of focus on individual samples invokes the
concept of sample-wise learnability: How easy is it to correctly learn each
sample (cf. PAC learnability)? In this paper, we approach the sample-wise
learnability problem within a deep learning context. We propose a measure of
the learnability of a sample with a given deep neural network (DNN) model. The
basic idea is to train the given model on the training set, and for each
sample, aggregate the hits and misses over the entire training epochs. Our
experiments show that the sample-wise learnability measure collected this way
is highly linearly correlated across different DNN models (ResNet-20, VGG-16,
and MobileNet), suggesting that such a measure can provide deep general
insights on the data's properties. We expect our method to help develop better
curricula for training, and help us better understand the data itself.
