Add `README.md`

README.md

+# fmpi
+
+[![license](https://img.shields.io/badge/license-0BSD-blue)](LICENSE)
+
+fmpi is an easy-to-use C library to create simple parallel programs from a
+sequential code written in a high-level functional language called Futhark.
+
+## Table of Contents
+
+- [Quick overview](#quick-overview)
+- [Getting Started](#getting-started)
+  - [Prerequisites](#prerequisites)
+  - [Installation](#installation)
+- [Documentation](#documentation)
+- [License](#license)
+
+## Quick overview
+
+Game of Life implemented with `fmpi`:
+
+Sequential code for Game of Life is written in Futhark in a file named `gol.fut`
+
+```ml
+entry gol [y][x] (xs: [y][x]u64): [][]u64 =
+    let res = tabulate_2d (y) (x) (\i j ->
+        if(i > 0 && i < (y-1) && j > 0 && j < (x-1)) then
+            let cnt =
+                xs[(i-1), (j-1)] + xs[(i-1), j] + xs[(i-1), (j+1)] +
+                xs[  i  , (j-1)] +       0      + xs[  i  , (j+1)] +
+                xs[(i+1), (j-1)] + xs[(i+1), j] + xs[(i+1), (j+1)]
+            in u64.bool ((cnt == 3) || ((xs[i, j] == 1) && (cnt == 2)))
+        else xs[i,j]
+    )
+    in res[1:(y-1), 1:(x-1)]
+```
+
+Futhark function is called inside a C program with the help of `fmpi`.
+
+```c
+#include <stdio.h>
+#include <stdlib.h>
+#include <fmpi.h> // Header to include to use fmpi
+#include "gol.h"  // gol.fut => gol.h
+
+#define STEP_CNT 20 // Number of Game of Life steps
+#define X_LEN 8     // Width of `in`
+#define Y_LEN 8     // Height of `in`
+
+// Declare the futhark `gol` function which has 1 input parameter
+FMPI_TASK_FUTHARK(gol, 1)
+
+int main(int argc, char * argv[])
+{
+    // fmpi initialization
+    struct fmpi_ctx * ctx = fmpi_init(&argc, &argv);
+    // Initial state of the Game of Life simulation
+    u64 in[] = {
+        0,1,0,0,0,0,0,0,
+        0,0,1,0,0,0,0,0,
+        1,1,1,0,0,0,0,0,
+        0,0,0,0,0,0,0,0,
+        0,0,0,0,0,0,0,0,
+        0,0,0,0,0,0,0,0,
+        0,0,0,0,0,0,0,0,
+        0,0,0,0,0,0,0,0,
+    };
+    // Number of elements in the in `in` array
+    #define in_size (sizeof(in)/sizeof(T))
+    // Array which will contain the result
+    u64 out[in_size] = {0};
+    // Register the `gol` task which has a square stencil of size 1 in each
+    // direction, a 2D array of size (X_LEN * Y_LEN) output parameter named `out`
+    // and a 2D array of of size (X_LEN * Y_LEN) output parameter named `in`
+    struct fmpi_task gol_task = FMPI_REGISTER_SYNC_TASK(
+        ctx, gol, fmpi_stencil_square(1),
+        fmpi_data_2d_out(ctx, out, X_LEN, Y_LEN),
+        fmpi_data_2d_in(ctx, in, X_LEN, Y_LEN)
+    );
+    // The task is run STEP_CNT times
+    for(size_t i = 0; i < STEP_CNT; i++) {
+        fmpi_run_task(ctx, &gol_task);
+    }
+    // Gather the results on the root node once the task is done
+    fmpi_task_finalize(ctx, &gol_task, FMPI_TASK_OP_GATHER);
+    // Final result is printed by the root node
+    if(fmpi_is_root(ctx)) {
+        for(size_t i = 0; i < in_size; i++) {
+            printf("%lu", out[i]);
+            if((i+1) % X_LEN == 0) {
+                printf("\n");
+            }
+        }
+    }
+    // Exit fmpi and then the program
+    fmpi_exit(&ctx);
+    return EXIT_SUCCESS;
+}
+```
+
+## Getting Started
+
+### Prerequisites
+
+- A `C11` compliant compiler is needed to compile the code due to the use of
+`_Generic` by `fmpi`.
+- MPI(e.g., [OpenMPI](https://www.open-mpi.org/), [MPICH](https://www.mpich.org/), [MVAPICH](https://mvapich.cse.ohio-state.edu/))
+- [Futhark](https://futhark-lang.org/)
+
+### Installation
+
+[Download](https://githepia.hesge.ch/raphael.bach/fmpi/-/archive/master/fmpi-master.zip) or
+clone the repository:
+
+```console
+git clone https://gitedu.hesge.ch/raphael.bach/fmpi.git
+```
+
+Install the library to the standard default location `/usr/local/include/fmpi`:
+
+```console
+make install
+```
+
+Or install them to a different path `/my/custom/path/include/fmpi`:
+
+```console
+make install prefix=/my/custom/path
+```
+
+Add `/usr/local/include/fmpi` or `/my/custom/path/include/fmpi` to your include
+paths.
+
+## Documentation
+
+Require Doxygen.
+
+```console
+make doc
+```
+
+Documentation will be available in `doc/doxygen`
+
+## License
+
+This project is licensed under the _very_ permissive [BSD Zero Clause License](LICENSE).