Lexxeous's MPI Ring:

Summary and Semantics:

This is a simple parallel processing program that creates a ring of communicative processes using C and MPI. It creates a ring, of user defined size Pn, between 3 and 8, inclusive (3 ≤ n ≤ 8). The ring is 0-indexed, therefore, the master process is labeled as P0, while the worker processes are labeled as P1 through Pn-1. The master process P0 will initiate the message ring by passing the original string and integer to its next immediate worker P1. The worker processes, P1 through Pn-1, will pass the string and the integer to their next neighbors after appending their rank and incrementing the integer. The master process P0 will receive the modified string and integer from Pn-1, append its rank, and increment the integer, one last time.

Expectations and Execution:

The program only expects 3 command line arguments. The first command line argument expects the executable. The second command line argument expects a user input string of length ≤ 100. The third command line argument expects an numeric, integer value. The steps for program execution are as follows:

• Reserve Pn processes on a computing node (I used a university hosted HPC server).
  • hpcshell --tasks-per-node=<Pn>
• Use make to call the comp target from Makefile for compilation.
  • make comp -> mpicc -o <executable> mpi_ring.c
• Use make to call the run target from Makefile for execution. Make sure to follow the expectations for the command line arguments, match Pn, and match the executable name.
  • make run -> mpirun -np <Pn> ./<executable> <string> <integer>
• Use make to call the clean target from Makefile to remove the executable from the current directory.
  • make clean -> rm <executable>

Result with 8 Processes:

Execution Commands:

>> hpcshell --tasks-per-node=8
>> make comp
   mpicc -o mpi_ring mpi_ring.c
>> make run
   mpirun -np 8 ./mpi_ring testing_ring 1

Output:

Starting MPI ring of size 8...
Original message: testing_ring
Original value: 8675309

Message at process 1: testing_ring1
Value at process 1: 8675310

Message at process 2: testing_ring12
Value at process 2: 8675311

Message at process 3: testing_ring123
Value at process 3: 8675312

Message at process 4: testing_ring1234
Value at process 4: 8675313

Message at process 5: testing_ring12345
Value at process 5: 8675314

Message at process 6: testing_ring123456
Value at process 6: 8675315

Message at process 7: testing_ring1234567
Value at process 7: 8675316

Message at process 0: testing_ring12345670
Value at process 0: 8675317

Result with 5 Processes:

Execution Commands:

>> hpcshell --tasks-per-node=5
>> make comp
   mpicc -o mpi_ring mpi_ring.c
>> make run
   mpirun -np 5 ./mpi_ring ring 5000

Output:

Starting MPI ring of size 5...
Original message: ring
Original value: 5000

Message at process 1: ring1
Value at process 1: 5001

Message at process 2: ring12
Value at process 2: 5002

Message at process 3: ring123
Value at process 3: 5003

Message at process 4: ring1234
Value at process 4: 5004

Message at process 0: ring12340
Value at process 0: 5005

Result with 3 Processes:

Execution Commands:

>> hpcshell --tasks-per-node=3
>> make comp
   mpicc -o mpi_ring mpi_ring.c
>> make run
   mpirun -np 3 ./mpi_ring string 80

Output:

Starting MPI ring of size 3...
Original message: string
Original value: 80

Message at process 1: string1
Value at process 1: 81

Message at process 2: string12
Value at process 2: 82

Message at process 0: string120
Value at process 0: 83

Result with 9 Processes:

Execution Commands:

>> hpcshell --tasks-per-node=9
>> make comp
   mpicc -o mpi_ring mpi_ring.c
>> make run
   mpirun -np 9 ./mpi_ring string 80

Output:

ERR:9:WRLDSZ >> Number of processes must be between 3 and 8 for ./mpi_ring.
--------------------------------------------------------------------------
MPI_ABORT was invoked on rank 0 in communicator MPI_COMM_WORLD
with errorcode 9.

NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes.
You may or may not see output from other processes, depending on
exactly when Open MPI kills them.
--------------------------------------------------------------------------
make: *** [run] Error 9

Result with 2 Processes:

Execution Commands:

>> hpcshell --tasks-per-node=2
>> make comp
   mpicc -o mpi_ring mpi_ring.c
>> make run
   mpirun -np 2 ./mpi_ring string 80

Output:

ERR:2:WRLDSZ >> Number of processes must be between 3 and 8 for ./mpi_ring.
--------------------------------------------------------------------------
MPI_ABORT was invoked on rank 0 in communicator MPI_COMM_WORLD
with errorcode 2.

NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes.
You may or may not see output from other processes, depending on
exactly when Open MPI kills them.
--------------------------------------------------------------------------
make: *** [run] Error 2

Result with too many command line arguments:

Execution Commands:

>> hpcshell --tasks-per-node=5
>> make comp
   mpicc -o mpi_ring mpi_ring.c
>> make run
   mpirun -np 5 ./mpi_ring ring 100 test

Output:

ERR:3:ARGC >> Wrong number of command line arguments.
Use ./<executable> <string> <integer> as format.
-------------------------------------------------------
Primary job  terminated normally, but 1 process returned
a non-zero exit code.. Per user-direction, the job has been aborted.
-------------------------------------------------------
--------------------------------------------------------------------------
mpirun detected that one or more processes exited with non-zero status, thus causing
the job to be terminated. The first process to do so was:

  Process name: [[17468,1],0]
  Exit code:    253
--------------------------------------------------------------------------

Result with an exceedingly long input string:

Execution Commands:

>> hpcshell --tasks-per-node=7
>> make comp
   mpicc -o mpi_ring mpi_ring.c
>> make run
   mpirun -np 7 ./mpi_ring s0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789 1

Output:

ERR:0:STR >> The second command line argument must be a string of size ≤ 100.
--------------------------------------------------------------------------
MPI_ABORT was invoked on rank 0 in communicator MPI_COMM_WORLD
with errorcode 0.

NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes.
You may or may not see output from other processes, depending on
exactly when Open MPI kills them.
--------------------------------------------------------------------------
make: *** [run] Error 0