done readme

Author: nicola-giuliani

README.md

@@ -2,7 +2,7 @@
 
 [![Build Status](https://travis-ci.org/mathLab/pi-BEM.svg?branch=master)](https://travis-ci.org/mathLab/pi-BEM)
 
-The library represents a parallel solver for the Laplace equation through Boundary Element Methods. We have developed the software on top of the deal.II library. 
+The library represents a parallel solver for the Laplace equation through Boundary Element Methods. We have developed the software in C++ on top of the [deal.II](https://github.com/dealii/dealii) library. 
 
 ## Provided features
 
@@ -15,15 +15,46 @@ We provide the following capabilities
 - Distributed memory (MPI) parallelisation of the standard collocation BEM for the Laplace equation.
 - Coupling with a FMM to get a performance improvement.
 - Hybrid Distributed (MPI) - Shared (TBB) memory parallelisation for the BEM-FMM code
+- Recovery of both primal (potential) and dual (potential normal derivative) unknowns.
+- L2 projection  of the full 3D potential gradient for post processing.
+- Extensive tuning via parameter file using the [deal2lkit](https://github.com/mathLab/deal2lkit) library 
+
 
 ## Code Structure
+We have subdivided the code in main classes to handle the many different aspects of a complete BEM simulation.
+
+- Driver. This class is in charge of organising the overall BEM simulation. It has interfaces with all the other classes in order to have a complete simulation.
+- ComputationalDomain. This class handles, and provides to the other classes, ONLY the geometry of the problem. In particular
+ - it handles the domain decomposition using a graph partitioning tool (METIS);
+ - it reads the domain from an external file.
+- BoundaryCondition. The class handling the boundary conditions. In particular
+	- it reads the boundary conditions for the potential and its normal derivative; 
+	- given the peculiarities of the BEM the boundary conditions represent the actual unknowns, thus it creates the vector containing the variables and fills them with the proper data;
+	- it performs the error analysis on both unknowns.
+
+- BEMProblem. This class is the core of the BEM simulation
+	- it receives the variables vector filled in with the proper boundary condition;
+	- it creates the codimension 1 functional space setting up the BEM;
+	- it solves the system using a preconditioned parallel GMRES solver;
+	- it eventually interacts with the FMM accelerator.
+- BEMFMA. This class handles the accelerator, in particular
+	- it sets up an hierarchical 3D space subdivision (octree);
+	- it receives two distributed vectors representinf the unknowns and performs a full FMM matrix vector product.
 
 ## Install Procedure
 In order to successfully compile the code you need 
 
 - to install the [deal.II](https://github.com/dealii/dealii) library allowing both for multiprocessors and multithreaded environment.
 - to install the Trilinos and Metis wrappers of the library, see the official [instructions](https://www.dealii.org/developer/readme.html) 
-- to install the pi-BEM library.
+
+Then you can clone the repository and compile it
+
+	git clone https://github.com/mathLab/pi-BEM.git
+	cd pi-BEM
+	mkdir build
+	cd build
+	cmake ../
+	make -j4
 
 After you have compiled your application, you can run