Github user woshilaiceshide commented on the pull request:
https://github.com/apache/spark/pull/1544#issuecomment-49959853
@mateiz, because in spark-v1.0.1, "spark.default.parallelism" is not
considered in class LocalBackend, which is assigned to totalCores, and
totalCores is derived from "local[N]". In spark-v1.0.1, if I want to increase
the default parallelism(p), I should increase N in "local[N]", which increases
the number(t) of tasks that can be launched in the only local executor, so
"spark.task.cpus"(c) comes in. Finally, I make the equation: p-(t-1)+1 = c*2 ,
which will be true when the split factor is big enough. Be sure to refer to
https://github.com/apache/spark/blob/v1.0.1/core/src/main/scala/org/apache/spark/scheduler/local/LocalBackend.scala
But, this bug is revised in the current master:
https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/scheduler/local/LocalBackend.scala
We use "local[N]" in our production, so we paied more attention to
"local[N]".
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