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[Minor] Fix comments for GraphX 2D partitioning strategy #3904

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[Minor] Fix comments for GraphX 2D partitioning strategy #3904

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6 changes: 3 additions & 3 deletions graphx/src/main/scala/org/apache/spark/graphx/PartitionStrategy.scala
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Expand Up @@ -32,9 +32,9 @@ trait PartitionStrategy extends Serializable {
object PartitionStrategy {
/**
* Assigns edges to partitions using a 2D partitioning of the sparse edge adjacency matrix,
* guaranteeing a `2 * sqrt(numParts)` bound on vertex replication.
* guaranteeing a `2 * sqrt(numParts) - 1` bound on vertex replication.
*
* Suppose we have a graph with 11 vertices that we want to partition
* Suppose we have a graph with 12 vertices that we want to partition
* over 9 machines. We can use the following sparse matrix representation:
*
* <pre>
Expand All @@ -61,7 +61,7 @@ object PartitionStrategy {
* that edges adjacent to `v11` can only be in the first column of blocks `(P0, P3,
* P6)` or the last
* row of blocks `(P6, P7, P8)`. As a consequence we can guarantee that `v11` will need to be
* replicated to at most `2 * sqrt(numParts)` machines.
* replicated to at most `2 * sqrt(numParts) - 1` machines.
*
* Notice that `P0` has many edges and as a consequence this partitioning would lead to poor work
* balance. To improve balance we first multiply each vertex id by a large prime to shuffle the
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