EE451 - Parallel and Distributed Computation -  PA4   - Solved

1.    Examples

Copy example files to your home directory.

1.    Login to HPC

2.    Copy

cp -r /project/xuehaiqi_652/examples .

3.    Goto examples cd examples

The openmp_example.c contains the OpenMP implementation of matrix vector multiplication.

1.    Login to HPC

2.    Compile

gcc -O3 -fopenmp openmp_example.c

3.    Run

srun -c8 ./a.out

The option -c specifies the number of CPUs allocated for a task. By default, the value is 1. For OpenMP program, the number of threads should equal the number of CPUs.

The mpi_examples folder includes the source codes used in discussions. To run an mpi

program, for example, the ‘scatter.c’, follow the steps:

1.    Login to HPC

2.    Setup MPI toolchain:

module purge module load intel/19.0.4 intel-mpi

3.    Compile

mpicc -O3 scatter.c

4.    Run

 
srun --exclusive --mpi=pmi2 -n4 ./a.out


The option -n specifies the number of tasks (processes). By default, the value is 1. There is 1 task per node (machine), but note that the -c option will change this default.

2.    Parallel Matrix Multiplication[50 points]

Parallelize the naive matrix multiplication which you implemented in PA 1 using OpenMP. Name the program as openmp.c. Take a screenshot.

•    The matrix size is 4K × 4K. Print out the execution time and the value of C[100][100] in your program.

•    Pass the number of threads p as a command line parameter [1].

•    Report the execution time for p = 1, 2, 4.

3.    Pass Message in a Ring [50 points]

Write an MPI program that passes a value around 4 processes using the following steps.

Name this program as mpi.c. Take a screenshot.

1.    Process 0 initializes Msg = 451 and prints value of Msg

2.    Process 0 sends the value of Msg to Process 1

3.    Process 1 receives the value of Msg, increases it by 1, prints the value and sends the current value of Msg to Process 2

4.    Process 2 receives the value of Msg, increases it by 1, prints the value and sends the current value of Msg to Process 3

5.    Process 3 receives the value of Msg, increases it by 1, prints the value and sends the current value of Msg to Process 0

6.    Process 0 receives the value of Msg from Process 3 and prints the value

The output messages look like (Note that your code is still correct if the order of messages is different):

•    Process 0: Initially Msg = 451

•    Process 1: Msg = 452

•    Process 3: Msg = 454

•    Process 2: Msg = 453

•    Process 0: Received Msg = 454. Done!