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Daniel Lemire commented on SPARK-11583: --------------------------------------- [~Qin Yao] The RoaringBitmap library is able to store a set containing all integers in an arbitrary range like [0,200000) using only a few bytes, orders of magnitude less than a Java BitSet. > Make MapStatus use less memory uage > ----------------------------------- > > Key: SPARK-11583 > URL: https://issues.apache.org/jira/browse/SPARK-11583 > Project: Spark > Issue Type: Improvement > Components: Scheduler, Spark Core > Reporter: Kent Yao > > In the resolved issue https://issues.apache.org/jira/browse/SPARK-11271, as I > said, using BitSet can save ≈20% memory usage compared to RoaringBitMap. > For a spark job contains quite a lot of tasks, 20% seems a drop in the ocean. > Essentially, BitSet uses long[]. For example a BitSet[200k] = long[3125]. > So if we use a HashSet[Int] to store reduceId (when non-empty blocks are > dense,use reduceId of empty blocks; when sparse, use non-empty ones). > For dense cases: if HashSet[Int](numNonEmptyBlocks).size < > BitSet[totalBlockNum], I use MapStatusTrackingNoEmptyBlocks > For sparse cases: if HashSet[Int](numEmptyBlocks).size < > BitSet[totalBlockNum], I use MapStatusTrackingEmptyBlocks > sparse case, 299/300 are empty > sc.makeRDD(1 to 30000, 3000).groupBy(x=>x).top(5) > dense case, no block is empty > sc.makeRDD(1 to 9000000, 3000).groupBy(x=>x).top(5) -- This message was sent by Atlassian JIRA (v6.3.4#6332) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org