T2SOLV: An enhanced package of solvers for the TOUGH2 family of codes

T2SOLV is an enhanced package of matrix solvers for the TOUGH2 family of codes.T2SOLV includes all the Preconditioned Conjugate Gradient (PCG) solvers used in T2CG1, the current solver package, as well as LUBAND, a new direct solver, and DLUSTB, a PCG solver based on the BiCGSTAB method. Additionally, T2SOLV includes the D4 grid numbering scheme and two sets of preprocessors. Results from test problems indicate that LUBAND is faster, more reliable and requires less storage than MA28, the BiCGSTAB solver is superior to the other PCG methods in T2SOLV, and that the preprocessors improve the performance of the PCG solvers and allow the solution of previously intractable problems.