Efficient parallel algorithms for Sparse Direct LLT Solvers are complex
and involve many tradeoffs. In this paper, we compare two solvers
called PSPASES and VPPdLLT on a
(virtual) AP3000, which is UltraSPARC-based. Both of these involve 4
stages: a reordering stage to minimize fill-in, a symbolic factorization
stage to determine the non-zero structure of the factored matrix, a
numerical factorization stage to compute the values of the non-zeroes,
and a triangular systems solution stage.
An overview of the algorithms and software structure of the two solvers
will be given, together with an analysis on the suitability of both for
machines such as the AP3000. VPPdLLT's performance compares favorably
on a 2-node virtual AP3000. An outline of how to tune and extend
VPPdLLT to larger processor configurations will then be presented.