Larry Xiao created SPARK-2981: --------------------------------- Summary: PartitionStrategy: VertexID hash overflow Key: SPARK-2981 URL: https://issues.apache.org/jira/browse/SPARK-2981 Project: Spark Issue Type: Bug Components: GraphX Affects Versions: 1.0.2 Reporter: Larry Xiao
In PartitionStrategy.scala a PartitionID is calculated by multiplying VertexId with a mixingPrime (1125899906842597L) then cast to Int, and mod numParts. The Long is overflowed, and when cast to Int: {quote} scala> (1125899906842597L*1).toInt res1: Int = -27 scala> (1125899906842597L*2).toInt res2: Int = -54 scala> (1125899906842597L*3).toInt res3: Int = -81 {quote} As the cast produce number that are multiplies of 3, the partition is not useable when partitioning to multiples of 3. for example when you partition to 6 or 9 parts: {quote} 14/08/12 09:26:21 INFO GraphXPartition: GRAPHX: psrc Array((0,4347084), (1,0), (2,0), (3,3832578), (4,0), (5,0)) 14/08/12 09:26:21 INFO GraphXPartition: GRAPHX: pdst Array((0,4347084), (1,0), (2,0), (3,3832578), (4,0), (5,0)) 14/08/12 09:21:46 INFO GraphXPartition: GRAPHX: psrc Array((0,8179662), (1,0), (2,0), (3,0), (4,0), (5,0), (6,0), (7,0), (8,0)) 14/08/12 09:21:46 INFO GraphXPartition: GRAPHX: pdst Array((0,8179662), (1,0), (2,0), (3,0), (4,0), (5,0), (6,0), (7,0), (8,0)) {quote} I think solution is to cast after mod. {quote} scala> (1125899906842597L*3) res4: Long = 3377699720527791 scala> (1125899906842597L*3) % 9 res5: Long = 3 scala> ((1125899906842597L*3) % 9).toInt res5: Int = 3 {quote} -- This message was sent by Atlassian JIRA (v6.2#6252) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org