This directory contains  the PSBLAS library, version 2.0
Version 1.0 of the library is described in:
S. Filippone, M. Colajanni
PSBLAS: A library for parallel linear algebra computation on sparse matrices
ACM Trans. on Math. Software, 26(4), Dec. 2000, pp. 527-550.

PLATFORMS: 

For the F77 compiler, we assume it supports DOUBLE COMPLEX and DO WHILE/ENDDO.
Practically all compilers do nowadays.  
The compilation process relies on the choice of an appropriate
Make.inc file; we have tested with AIX XLF, Intel ifc/Linux, Lahey
F95/Linux  and  Nag f95/Linux. If you succeed in compiling with other
compiler/operating systems please let us know. 

IBM SP2.
The library has been tested on an IBM SP2 with XLC and XLF
compilers, and a version of the BLACS based on MPI.
The rather baroque setting 
 F90=xlf90 -qsuffix=f=f90
in Make.inc.rs6k takes care of the f90 extension. 
WARNING: xlf 8.1 introduced a performance bug, whereas a Fortan 90
code calling a  Fortan 77 code would incur spurious array copies;
please make sure your system has the PTF xlf 8102 installed. 


LINUX:

There finally exist a GNU Fortran 95 implementation: we are using the
development snapshots from GCC 3.5.0 since July 2004, and it appears
to work. This is on its way to become the reference platform. 

We compiled with egcs G77/GCC and mpich-1.2.0, 1.2.1,  1.2.2 and 1.2.4.
With some versions of GCC, g77 chokes on SRC/SERIAL/dcsdp.f; this
problem seems to have disappeared in recent GCC distributions. 



Vast F90/Linux and PGI f90/Linux are now obsolete, in that we have a
NULL() initialization for pointers that is outsied strict F90; they
cannot be used any longer.
For the PGI compilers, we used them in conjunction with gcc, NOT
pgcc. Note that with pgi 3.6 we have horrible performance, due to
spurious array copies when calling Fortran 77 codes from Fortran 90;
this is fixed in version 4. 

The Lahey version we got access to (6.0 and 6.1) seems to suffer from
the same extra copies problem; this is most apparent in the matrix
build process.  

For the Intel compilers, we used ifc version 7.0 and 7.1; with version 6.0 
you need to change the way modules are handled, but we recommend to migrate
to the new version anyway. Moreover, with versions prior to 7.1, there
is a strange error in pargen/ppde90: the compiler did not like the
INTERFACE for the dummy argument subroutine PARTS, it wanted an
EXTERNAL specification. Again, please move to 7.1.


Testing of  NAG f95 versions is still incomplete.  



DOCUMENTATION

See userguidef90.ps. 
Please consult the sample programs, especially TEST/pargen/ppde90.f90. 


OTHER SOFTWARE CREDITS 

We include our modified implementation of some of the Sparker (serial
sparse BLAS)  material,  e.g. Jagged diagonal, plus a number of
extensions of our own design. The original file spblas.f can be
downloaded from matisa.cc.rl.ac.uk; of course any bugs in our
implementation are our own to fix.  The main reference for the serial
sparse BLAS is: 
Duff, I., Marrone, M., Radicati, G., and Vittoli, C.
Level 3 basic linear algebra subprograms for sparse matrices: a user 
level interface
ACM Trans. Math. Softw., 23(3), 379-401, 1997.

We have had good results with  the METIS library, which can be
obtained from
http://www-users.cs.umn.edu/~karypis/metis/metis/main.html 



NEW: 

- Reviewed the interfaces: in the tools section we really need the
  POINTER attribute for dense vectors, but not in the computational
  routines; taking it  out allows more flexibility. Besides, this acts
  as a workaround for a bug on Linux/VAST: as of version 
  "vf90  Personal   V3.4N5" the DOT and NRM functions had to be
  transformed into subroutines whenever the vectors had the POINTER
  attribute; now both subroutine and function versions work.  

- Added more methods: CGS, BiCGSTAB(L), BiCG

- We now have a new Preconditioner F90 routine; diagonal scaling works
  with COO, CSR and JAD; ILU works with JAD, but is more expensive in terms 
  of memory space

- We added some extensions to compute multiple DOTs and AMAXs at once;
  they can be useful in solving vector equations (e.g. momentum
  equation in fluid dynamics).   
- Halo data exchange in F90_PSHALO can now be applied to integer data;

- There is an update capability for cases where the same sparsity
  pattern is reused (e.g.  multiple time steps over a discretization
  mesh which maintains a constant topology) 

- We added a test program to read and solve sparse matrices from files in
  Matrix-Market format (for details see http://math.nist.gov/MatrixMarket/) 




TODO:


1. Extend the C/F77 interface for character data (some Fortran
   compilers don't just pass a pointer and a hidden length!) 

2. Provide more general factorizations. 




The PSBLAS team. 


Credits:
Salvatore  Filippone
Michele    Colajanni
Alfredo    Buttari
Fabio      Cerioni
Stefano    Maiolatesi
Dario      Pascucci