IMPROVING SOLVE TIME OF AGGREGATION-BASED ADAPTIVE AMG

This paper proposed improving the solve time of the bootstrap AMG proposed previously by the authors. This is achieved by incorporating the information, set of algebraically smooth vectors, generated by the bootstrap algorithm, in a single hierarchy by using sufficiently large aggregates, and these aggregates are compositions of aggregates already built throughout the bootstrap algorithm. The modified AMG method has comparable convergence properties to the original bootstrap one, however with better efficiency. The improvement in solve time with respect to the original bootstrap AMG is illustrated on some difficult linear systems arising from discretization of vector function elliptic Partial Differential Equations (PDEs) in both 2d and 3d.