Introduction to Programming with MPI
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Practical Exercise 15 (One-Sided Communication)
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For general instructions, see the introduction to the collective
practicals.



Question 1
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1.1 Write a program that creates an integer array of length 3 in each
process with the following data:

        Process 0:    11, 12, 13
        Process 1:    21, 22, 23
        Process 2:    31, 32, 33
        Process 3:    41, 42, 43

Use one-sided communication (MPI_Put) with collective synchronisation
(i.e. MPI_Fence) to copy the first element of the array to the current
process, rotate the second element of the array to the next process
(with the last going to the first) and the third element to the previous
process (with the first process going to the last).  I.e. the result
should be:

        Process 0:    11, 42, 23
        Process 1:    21, 12, 33
        Process 2:    31, 22, 43
        Process 3:    41, 32, 13


1.2 Change the program to use MPI_Get.


1.3 Change the program to do a transposing reduction, with the first
process receiving the product of the first elements of the array on each
process, and so on.  I.e. the result should be:

        Process 0:    293601    [ = 11*21*31*41 ]
        Process 1:    354816    [ = 12*22*32*42 ]
        Process 2:    424281    [ = 13*23*33*43 ]
        Process 3:    1


Question 2
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2.1 Take a copy of the program you wrote in question 3.1 in practical
exercise 4, that was called 'Daggoo', and change it to use one-sided
communication.  This is simply repeating 1.1 in practical exercise 7, in
a one-sided communication variant.  The result should be functionally
equivalent.

There are no specimen answers to this question.

2.2 Take a copy of the program you wrote in question 5.1 in practical
exercise 3, that was called 'Stubb', and write a replacement for
MPI_Alltoall, using one-sided communication.  This is simply repeating
exercise 5.1 in practical exercise 4 and exercise 2.1 in practical
exercise 7, in a one-sided communication variant.  The result should be
functionally equivalent.

There are no specimen answers to this question.