README update

README.md

@@ -1,3 +1,21 @@
 # NOAA/NASA Domain Specific Language middleware
 
-Use `git clone --recurse-submodule` to pull all vetted versions of the submodules used by `ndsl`
+NDSL is a middleware for climate and weather modelling developped conjointment by NOAA and NASA. The middleware brings together [GT4Py](https://github.com/GridTools/gt4py/) (the `cartesian` flavor), an ETH CSCS's stencil DSL, and [DaCE](https://github.com/spcl/dace/), an ETH SPCL's data flow framework, both developped for high-performance and portability. On top of those pillars, NDSL deploys a series of optimized APIs for common operations (Halo exchange, domain decomposition, MPI...) and a set of bespoke optimizations for the models targeted by the middleware.
+
+## Battery-included for FV-based models
+
+Historically NDSL was developed to port the FV3 dynamical core on the cube-sphere. Therefore, the middleware ships with ready-to-execute specilization for models based on cube-sphere grid and FV-based model in particular.
+
+## Quickstart
+
+NDSL submodules `gt4py` and `dace` to point to vetted versions, use `git clone --recurse-submodule`.
+
+NDSL is __NOT__ available on `pypi`. Installation of the package has to be local, via `pip install ./NDSL` (`-e` supported). The packages has a few options:
+
+- `ndsl[test]`: installs the test packages (based on `pytest`)
+- `ndsl[develop]`: installs tools for development and tests.
+
+Tests are available via:
+
+- `pytest -x test`: running CPU serial tests (GPU as well if `cupy` is installed)
+- `mpirun -np 6 pytest -x test/mpi`: running CPU parallel tests (GPU as well if `cupy` is installed)