heat-conduction-solver

Parallel using MPI and OpenMP

Compiling and Running

Step 1. Compile rbbreakup.c utility that splits the input file into files with subgrids:

cc -Wall rbbreakup.c -o rbb -O

Step 2. Run rbb on an input file with desired number of i- and j- chunks:

./rbb -ichunk 2 -jchunk 2 -in input.txt

This will generate four files, input.txt.0, input.txt.1, input.txt.2 and input.txt.3, that will be processed by four MPI ranks.

Here, -ichunk specifies in how many "columns" we split the grid, -jchunk – in how many "rows". When ichunk = 1 and jchunk = 2, the grid stays the same.

When ichunk = 1 and jchunk = 2, the division will look like this:

input.txt.0
input.txt.1

When ichunk = 2 and jchunk = 2, the division will look like this:

input.txt.0	input.txt.1
input.txt.2	input.txt.3

Step 3. Compile stencil.c:

mpicc -fopenmp -o s stencil.c

Step 4. Run:

mpirun --bind-to none -n 4 ./s -inp input.txt -res output.txt -threads 4 -ichunk 2 -jchunk 2

Here, -n specifies the number of cores used by MPI, which should be equal to the number of subgrids (= files), and ichunk * jchunk = n. -threads is the number of threads used by OMP. ichunk and jchunk is the number of blocks. Best performance is achieved when threads == n.