Shuffle process on the map side
Partitioning, sorting, merging
Merging and merging are different operations
. Merging overflow write files
Merging: <“a”, 1>, <“a”, 1> Get <“a”, 2>
Merge: < "A", <1,1 >>
There is a local disk in the map
, only put it on the disk if it cannot be stored in the map
MapReduce execution process:
slice 0 ~ M
Example: wordcount
input: words
output: words, word frequency
Reduce is
a multiplication of matrix and vector
