Quiz Questions ITCS 4145/5145 Parallel Programming MPI ITCS 4/5145 Parallel Programming, UNC-Charlotte, B. Wilkinson, 2012, QuizQuestions2a.ppt June 15, 2012

What is the name of the default MPI communicator? DEF_MPI_COMM_WORLD It has no name. DEFAULT_COMMUNICATOR COMM_WORLD MPI_COMM_WORLD

What does the MPI routine MPI_Comm_rank() do? It compares the supplied process ID with that of the process and returns TRUE or FALSE. It returns an integer that is number of processes in the specifed communicator. The number is returned as an agument. It converts the Linux process ID to a unique integer from zero onwards. It returns an integer that is the rank of the process in the specifed communicator. The integer is returned as an agument. It returns the priority number of the process from highest (0) downwards.

Name one MPI routine that does not have a named communicator as a parameter (argument). MPI_Send() MPI_Bcast() MPI_Init() MPI_Barrier() None - they all have a named communicator as a parameter. none of the other answers

What is the purpose of a message tag in MPI? To provide a mechanism to differentiate between message-passing routines written by different programmers To count the number of characters in a message To indicate the type of message To provide a matching mechanism differentiating between message sent from one process to another process

When does the MPI routine MPI_Recv() return? After the arrival of the message the routine is waiting for but before the data has been collected. Never Immediately After a time specified in the routine. After the arrival of message the routine is waiting for and the data collected.

What is meant by a blocking message passing routine in MPI? The routine returns when all the local actions are complete but the message transfer may not have completed. The routine returns immediately but the message transfer may not have completed. The routine returns when the message transfer has completed. The routine blocks all actions on other processes until it has completed its actions. None of the other answers.

What is meant by a non-blocking (or asynchronous) message passing routine in MPI? The routine returns when all the local actions are complete but the message transfer may not have completed. The routine returns immediately but the message transfer may not have completed. The routine returns when the message transfer has completed. The routine blocks all actions on other processes until it has completed its actions. None of the other answers.

In the routine: MPI_Send(message,13,MPICHAR,x,10, MPI_COMM_WORLD); when can x be altered without affecting the message being transferred? Never. After the routine returns, i.e. in subsequent statements Anytime When the message has been received None of the other answers

What does the routine MPI_Wtime() do? Waits a specific time before returning as given by an argument. Returns the elapsed time from some point in the past, in seconds. Returns the elapsed time from the beginning of the program execution, in seconds. Returns the time of the process execution. Returned the actual time of day None of the other answers.

Under what circumstance might an MPI_Send() operate as an MPI_Ssend()? If the available message buffer space becomes exhausted. If you specify more than a thousand bytes in the message. If the tags do not match. When the "synch" parameter is set in the parameter list of MPI_Send() Never

What does the MPI routine MPI_Barrier() do? Waits for all messages to be sent and received. Will cause processes to wait for all processes within the specific communicator to call the routine. Then all processes send a message to the master process and continue. Makes a process to execute slower to allow debugging Waits for a specified amount of time. Will cause processes after calling MPI_Barrier() to wait for all processes within the specific communicator to call the routine. Then all processes are released and are allowed to continue.