# deqn – a simple 2D heat diffusion simulation
`deqn` is a program that solves the 2D diffusion equation on a structured mesh.?deqn????????????????
Three different schemes are provided:
1. A simple explicit update scheme,
2. An iterative (matrix-free) Jacobi scheme, and
3. A scheme that uses the HYPRE library to solve the system of linear equations.
## Building
– To build the first two schemes, just type `make`.
– To build `deqn` with HYPRE, set the variable `HYPRE_DIR` in the Makefile, and
ensure that the `CXXFLAGS` variable defines `HAVE_HYPRE`.
## Running
Using your favourite MPI flavour:
mpirun -n 4 ./deqn
## Input Files
The file `test/square.in` demonstrates the supported input parameters, most importantly:
– `scheme
– `vis_frequency
– `subregion