|   | 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 |