What is wrong with ps when the number of data is large?

[cstur4]

=========== model distributed ==============
executor removed: 19
==== [INFO] [12/07/2016 14:35:46.305] [PSManager] parameter server terminated: -1, null
==== [INFO] [12/07/2016 14:35:46.307] [Monitor] Monitor stopped
[ERROR] [07/12/2016 14:35:46.306] [monitor-system-akka.actor.default-dispatcher-4] [akka://monitor-system/user/monitor] -1
java.lang.ArrayIndexOutOfBoundsException: -1
at com.intel.distml.platform.PSManager.serverTerminated(PSManager.java:141)
at com.intel.distml.platform.PSManager.serverTerminated(PSManager.java:136)
at com.intel.distml.platform.MonitorActor.onReceive(MonitorActor.java:356)
at akka.actor.UntypedActor$$anonfun$receive$1.applyOrElse(UntypedActor.scala:167)
at akka.actor.Actor$class.aroundReceive(Actor.scala:467)
at akka.actor.UntypedActor.aroundReceive(UntypedActor.scala:97)
at akka.actor.ActorCell.receiveMessage(ActorCell.scala:516)
at akka.actor.ActorCell.invoke(ActorCell.scala:487)
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:238)
at akka.dispatch.Mailbox.run(Mailbox.scala:220)
at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397)
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

==== [INFO] [12/07/2016 14:35:46.309] [Monitor] Monitor created, psCount:20