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 se lf-equilibrating fluxes for arbitrary h-p finite element approximation s. 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 perfe ctly suited to parallel implementation. The algorithm can be applied i n both two and three dimensions for unstructured, k-irregular meshes a nd elements of non-uniform degree. Finally, it is shown that the imple mentation of the flux equilibration algorithm can take advantage of ca lculations already performed in obtaining the finite element approxima tion itself.