Yekun's Note

Machine learning notes and writeup.

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It is wasteful to store zeros elements in a sparse matrix, especially for incrementally data. When constructing tf-idf and bag-of-words features or saving graph ajacent matrix, non-efficient sparse matrix storage might lead to the memory error. To circumvent this problems, efficient sparse matrix storage is a choice.

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The brain has about 1014 synapses and we only live for about 109 seconds. So we have a lot more parameters than data. This motivates the idea that we must do a lot of unsupervised learning since the perceptual input (including proprioception) is the only place we can get 105 dimensions of constraint per second.
(Geoffrey Hinton)

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