34 lines
763 B
Plaintext
34 lines
763 B
Plaintext
|
|
||
|
|
Exercise 'ping pong'
|
||
|
|
~~~~~~~~~~~~~~~~~~~~
|
||
|
|
|
||
|
|
- Write a program in which two processes repeatedly pass a message back and
|
||
|
|
forth.
|
||
|
|
|
||
|
|
- Insert timing calls to measure the time taken for one message
|
||
|
|
(send+receive).
|
||
|
|
|
||
|
|
- Investigate how the time taken varies with the size of the message.
|
||
|
|
|
||
|
|
- Use message sizes 1, 2, 4, 8, 16, 32, ..., ~1 million
|
||
|
|
or 1, 10, 100, 1000, ..., 1 million
|
||
|
|
|
||
|
|
- Loop over message sizes
|
||
|
|
|
||
|
|
- In the loop time this block of code with MPI_Wtime()
|
||
|
|
|
||
|
|
MPI_Send(...);
|
||
|
|
MPI_Recv(...);
|
||
|
|
|
||
|
|
- Print out a table: message_size transfer_time
|
||
|
|
|
||
|
|
- Extra task: produce a graphical plot with double logarithmic axes for
|
||
|
|
transfer_time(message_size)
|
||
|
|
|
||
|
|
- Timers:
|
||
|
|
|
||
|
|
C : double MPI_Wtime(void);
|
||
|
|
Fortran : real(8), external :: mpi_wtime()
|
||
|
|
|
||
|
|
see also: MPI_Wtick()
|