message: adjust the content of README in miniapps/solvers
diff: -This miniapp implements some solvers for the discrete saddle point problems
  -arised from mixed finite element discretization of the Darcy's flow, and
  -compares the relative performance of the solvers.
  + Finite Element Discretization Library
  + __
  + _ __ ___ / _| ___ _ __ ___
  + | '_ ` _ \ | |_ / _ \| '_ ` _ \
  + | | | | | || _|| __/| | | | | |
  + |_| |_| |_||_| \___||_| |_| |_|
  -The saddle point problem has a block structure of the form
  - [ M B^T ] [u] = [f]
  - [ B 0 ] [p] = [g]
  + https://mfem.org
  -The solvers included:
  +This directory contains some sophisticated solvers for discrete problems
  +generated by MFEM.
  -1. The divergence free solver.
  +The miniapp block-solvers compares the relative performance of some solvers for
  +the discrete saddle point problems arised from the mixed finite element
  +discretization of the second order scalar elliptic problem
  + -div(K grad p) = r.h.s.
  +The user can customize the problem settings by providing the mesh, the
  +coefficient K, and the essential/natrual boundary assignment.
  +
  +The discrete saddle point problem has a block structure of the form
  + [ M B^T ] [u] = [g]
  + [ B 0 ] [p] = [f]
  +The solvers for the above block system include:
  +
  +1. The divergence free solver (both coupled and decoupled modes).
  The idea of the solver is to exploit a multilevel decomposition of the
  Raviart-Thomas finite element space to find a particular flux solution
  satisfying the divergence constraint B u_p = f, and then solve the remaining
  @@ -19,10 +33,10 @@ The solvers included:
  The multilevel decompositions of the Raviart-Thomas and discrete L2 space are
  given by DFSData, see the documentation in div_free_solver.hpp for more
  - details. In block_solver_comparison.cpp, the data are generated geometrically
  - through mesh refinement and collection of "TransferOperators" of the spaces,
  - This process is done in DFSSpaces. In general, the multilevel decompositions
  - can also be obtained via element agglomeration (e.g., use ParElag).
  + details. In block-solvers.cpp, the data are generated geometrically through
  + mesh refinement and collection of "TransferOperators" of the spaces, This
  + process is done in DFSSpaces. In general, the multilevel decompositions can
  + also be obtained via element agglomeration (e.g., use ParElag).
  For more details see
  [1]. Vassilevski, Multilevel Block Factorization Preconditioners (Appendix F.3),
  