README_charm

Authors: Jonathan Lifflander and Phil Miller

Compilation:
============
Set the CHARMC environment variable to point at
charm_installation/bin/charmc, and run make. This will build the
sequential, MPI, and Charm++ versions.

Guide to the Charm++ code:
==========================

- hpccg.ci:

Describes the main parallel control flow of the CG algorithm,
including the sparse matrix-vector multiplication with exchange of x
elements, and the reduction of residuals from global dot
products. Equivalent to main.cpp, HPCCG.cpp, and
exchange_externals.cpp from the sequential/MPI code.

- charmHpccg.cpp:

Contains the code for exchanging information of which chares will need
which elements of x for the SpMV in each iteration, as well the
mainchare constructor called at startup. Equivalent to
make_local_matrix.cpp from the MPI code, and part of main.cpp.

- charmHpccg.h:

Contains class and data structure declarations for the chares used in
the algorithm.

Sequential code used from the original:
=======================================

- HPC_Sparse_matrix.hpp: defines the CSR matrix data structure

- HPC_sparsemv.{hpp,cpp}: implements the sequential sparse
  matrix-vector multiplication on HPC_Sparse_matrix and a simple
  contiguous vector

- make_local_matrix.cpp: factored-out identify_externals() function
  for identifying needed elements of x that are not also kept locally.

- ddot.cpp, waxpby.cpp: sequential vector dot-product and addition
  kernels