I have a graph and am trying to take a random sample of vertices without
replacement, using the RDD.sample() method

verts are the vertices in the graph

>  val verts = graph.vertices

and executing this multiple times in a row 

>  verts.sample(false, 10000.toDouble/v1.count.toDouble,
> System.currentTimeMillis).count

yields different results roughly each time (albeit +/- a small % of the
target)

why does this happen? Looked at PartionwiseSampledRDD but can't figure it
out

Also, is there another method/technique to yield the same result each time? 
My understanding is that grabbing random indices may not be the best use of
the RDD model



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