Exercises

1

Modify program greetings discussed in section 5.2.2 so that the master process receives the messages not out of order but in the order that agrees with the ranking of the senders.

2

Write an MPI program in which processes fill their send buffers with random integers instead of greeting strings. Make the send buffers (and the corresponding receive buffer of the master process) 1,048,576 integers long. Make the master process append the received strings of random integers to an external file, the way that the program mkrandfile discussed in section 3.4.3worked.

Hint

You will have to replace MPI_CHAR with MPI_INT in MPI_Send and MPI_Recv. Remember that the length of send and receive buffers must be given in terms of the number of items of a type specified by the next argument, not in bytes.

Hint

Use the process rank number so that a different seed for function srand is generated within each MPI process. Otherwise they will all generate identical strings of pseudo-random integers.

Hint

Do not make the master process generate any numbers. It will be busy enough collecting data and writing the file.