week10

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stochastic gradient descent : for dealing with large datasets - where batch gradient descent will be slower; because batch uses all 'm' examples in each iteration;

randomly shuffle dataset

then use below algorithm : use 1 data set for each iteration

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mini-batch gradient descent:

for m = 300,000,000 (say US population data)

use : b =10 and perform batch gradient

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how to monitor stochastic gradient?

plot cost (thetai , xi) averaged over last 1000 examples

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online learning: learning based on user data through online

find p(y=1 |x) ;

repeat forever {

given x, y corresponding to user;

update theta;

}

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application:

predicted click thru rate:

for customer search say a phone :

show 10 best guesses that user may like :

find p(y=1|x ; theta) : how many links user clicked that was shown

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Map reduce:

divide training set data into equal proportions

send each data set to a computer for computing the cost

then combine all the cost in a single server

use this approach to speed up the computation

can be used within a single computer with mulitple cores