|
CMU-CS-97-133
Computer Science Department
School of Computer Science, Carnegie Mellon University
CMU-CS-97-133
Parallel Gaussian Elimination for Linear Work and Fill
Claudson Bornstein, Bruce Maggs, Gary Miller, Ramomoorthi Ravi*
May 1997
CMU-CS-97-133.ps
Keywords: Linear fill, height, parallel, interval graphs,
chordal graphs, gaussian elimination
This paper presents an algorithm for finding parallel
elimination orderings for Gaussian elimination. Viewing a system of
equations as a graph, the algorithm can be applied directly to
interval graphs and chordal graphs. For general graphs, the algorithm
can be used to parallelize the ordering produced by some other
heuristic such as minimum degree. In this case, the algorithm is
applied to the chordal completion that the heuristic generates from
the input graph. In general, the input to the algorithm is a chordal
graph G with n nodes and m edges. The algorithm
produces an ordering with height at most O(log3 n)
times optimal, fill at most O(m), and work at most
O(W*(G)), where W * (G) is the
minimum possible work over all elimination orderings for G.
Experimental results show that when applied after some other heuristic,
the increase in work and fill is usually small. In some instances the
algorithm obtains an ordering that is actually better, in terms of work
and fill, than the original one. We also present an algorithm that
produces an ordering with a factor of log n less height, but
with a factor of O(\/log n) more fill.
34 pages
*Graduate School of Industrial Administration,
Carnegie Mellon University
|