amg4psblas/README

This directory contains  the MLD2P4 set of preconditioners, version 2.1

WHAT'S NEW

Version 2.1
   1. The multigrid preconditioner now include fully general V- and W-
      cycles. We also support K-cycles, intended to be used in
      conjunction with Flexible CG available in PSBLAS 3.5.
   2. The smoothers now include popular 
      variants such as Jacobi, forward and backward  hybrid
      Gauss-Seidel (intra-process Gauss-Seidel, inter-process
      block-Jacobi).
   3. The  PRE and POST specification for smoothers can now be 
      specified independently of each other: you can even specify
      different  smoothers for PRE and POST (e.g. forward Gauss-Seidel
      PRE with backward Gauss-Seidel POST). The default is to
      have the specs apply to both PRE and POST. 


Version 2.0.

   Finally moved to F2003, with the support of PSBLAS3.
   There are a few minor differences at user level: 
   1. In the configure step, you should specify the INSTALL directory
      of PSBLAS version 3.4, not the source directory;
   2. In the various makefiles, libmld_prec.a should now be used in
      addition (and in front of) libpsb_prec.a, and no longer in
      place of it.
   3. As for the basic usage, this is practically identical to the
      previous version(s).  
   
   You should use the same MPI/serial compilers that were used for the
   PSBLAS installation. 
   The Fortran 2003 support means that it is far easier to develop and
   integrate new solvers and smoothers; you need to take one of the
   existing solvers/smoothers as a model, develop your own by
   changing/replacing the model contents, and then pass the new object
   to the PREC%SET() method which will copy into the internals, as per
   the PROTOTYPE design pattern. Take a look at the test/newslv
   directory to see an example. It's easier done than said!

   Versions known to work: 
   UMFPACK:      5.4
   SuperLU:      4.3 and 5.0
   SuperLU_Dist: 3.3 and 4.2
   Note that with SuperLU_Dist you will probably need to add further
   link options, e.g. the ParMetis library or the openmp runtime;
   you can do this using the configure option --with-extra-libs

In version 1.1:
-  The MLD_SIZEOF() function has been redefined to be INTEGER(8), so
   as to be able to measure large data sets.
-  The internals of the multilevel preconditioner have been repackaged
   in a more structured fashion; no changes are needed in the user
   code.
-  Note that we now need version 2.3.1 of PSBLAS.
   

To compile:
0. Unpack the tar file in a directory of your choice (preferrably
   outside the main PSBLAS directory).
1. run configure --with-psblas=<ABSOLUTE path of the PSBLAS install directory>
   adding the options for SuperLU, SuperLU_Dist, UMFPACK as desired.
2. Tweak Make.inc if you are not satisfied.

3. make; 

4. Go into the test subdirectory and build the examples of your choice.

Notes:

- The single precision version is  supported only by SuperLU; thus, even
  if you specify at configure to use UMFPACK or SuperLU_Dist, the
  corresponding preconditioner options will be available only from the
  double precision version.

- A program that was using the PSBLAS precoditioners needs no source
  code changes, but should be recompiled. If the new preconditioner
  (or preconditioner options, such as ILU(N) factorization) are
  required, only the type of the preconditioner object and its
  setup/build/free calls should be updated; the rest of the
  application continues to make use of the PSBLAS existing
  interfaces. 



CREDITS

developed by 
Salvatore  Filippone 
Pasqua     D'Ambra
Daniela    di Serafino
Alfredo    Buttari