apache/spark — pull request #3799 by XuTingjun (2014-12-25 08:22:20+00:00)
Title: [SPARK-1507][YARN]specify num of cores for AM

I add some configurations below.
spark.yarn.am.cores/SPARK_MASTER_CORES/SPARK_DRIVER_CORES for yarn-client mode;
spark.driver.cores for yarn-cluster mode.