A POSTERIORI ERROR ESTIMATORS FOR 2ND-ORDER ELLIPTIC-SYSTEMS .2. AN OPTIMAL ORDER PROCESS FOR CALCULATING SELF-EQUILIBRATING FLUXES

We present full details of an algorithm which can be used to obtain self-equilibrating fluxes for arbitrary h-p finite element approximations. All of the calculations axe performed on a local scale, yielding an optimal order process-O(n), where n is the number of elements in the mesh. Owing to the local nature of the process, the algorithm is perfectly suited to parallel implementation. The algorithm can be applied in both two and three dimensions for unstructured, k-irregular meshes and elements of non-uniform degree. Finally, it is shown that the implementation of the flux equilibration algorithm can take advantage of calculations already performed in obtaining the finite element approximation itself.