“…ILUTP Mem allows the user to set the values of 3 parameters that together control the memory required, and the accuracy provided, by the preconditioner; we used a range of values for lfil (0,1,2,3,4,5), droptol (0,.001,.01,.1), and pivtol (0,.1,1). In addition, before computing the ILU factorization, matrices were first permuted and scaled using MC64 [10,11] for stability, and then using COLAMD [12,13] for sparsity. Note that by using value-based ILU preconditioners, instead of the level-based ILU preconditioners used in [5], we are working with a much larger number of parameter values.…”