mapreduce - Mappers, Reducers, FIlters -


I know that using the function to map / reduce the algorithm and its use, which is called Mapper and Reduce But I think people use the word filter.

Is the filter equal to the mappers or is there a significant difference?

A filter is like a map for which the passed function is always a "function function" The function which is "yes" or "does not give" for the question "is it here?"

In other words, defined as a set {x | X and ISIN; X and p (x) }. The filter sets the base, to see that P (x) is correct, and only returns the members to whom this is true.

then { x | x is a natural number and weird ( x )} {1,3,5,7 ...}

A map performs an arbitrary task, so you can think of it as if it was {y. X and ISIN; X and y = f (x) }.

then { y | x is a natural number and y = x and sup2; } is {1,4,9,16, ...}.


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