Hands-on: Collective operations

In this exercise we test different routines for collective communication.

Source code for this exercise is located in mpi/collectives/

First, write a program where rank 0 sends an array containing numbers from 0
to 7 to all the other ranks using collective communication.

Next, we continue with four MPI tasks with following initial data vectors:

Task 0:	0	1	2	3	4	5	6	7
Task 1:	8	9	10	11	12	13	14	15
Task 2:	16	17	18	19	20	21	22	23
Task 3:	24	25	26	27	28	29	30	31

In addition, each task has a receive buffer for eight elements and the values
in the buffer are initialized to -1. Implement a program that sends and
receives values from the data vectors to receive buffers using a single
collective communication routine for each case, so that the receive buffers
will have the following values. You can start from the skeleton file
skeleton.py.

Case 1

Task 0:	0	1	-1	-1	-1	-1	-1	-1
Task 1:	2	3	-1	-1	-1	-1	-1	-1
Task 2:	4	5	-1	-1	-1	-1	-1	-1
Task 3:	6	7	-1	-1	-1	-1	-1	-1

Case 2

Task 0:	-1	-1	-1	-1	-1	-1	-1	-1
Task 1:	0	1	8	9	16	17	24	25
Task 2:	-1	-1	-1	-1	-1	-1	-1	-1
Task 3:	-1	-1	-1	-1	-1	-1	-1	-1

Case 3

Task 0:	8	10	12	14	16	18	20	22
Task 1:	-1	-1	-1	-1	-1	-1	-1	-1
Task 2:	40	42	44	46	48	50	52	54
Task 3:	-1	-1	-1	-1	-1	-1	-1	-1

Tip: create two communicators