“…For clarity of presentation, we assume that the partitions are of equal size m and that each overlap is of size τ . Thus, we can rewrite (1) as two linear systems (4) (5) where we choose the adjustment vector y such that the solution of the lower part of (4) coincides with the upper part of (5), in other words, (6) Let us assume, for now, that each overlapped partition is nonsingular, and that (7) Thus, using (4), (5) and (6) we obtain the balance system (8) (9) (10) Notice that once the balance system (8) is solved for y, linear systems (4) and (5) can be solved independently in parallel. Since the coefficient matrix M is not available explicitly, we use a modified iterative method to solve the balance system (8), where we compute the residual and matrix-vector products as described below.…”