Multi-Frontal Direct Solver Algorithm for Tri-Diagonal and Block-Diagonal One-Dimensional Problems. One-Dimensional Non-Stationary Problems. Multi-Frontal Direct Solver Algorithm for Multi-Diagonal One-Dimensional Problems. Multi-Frontal Direct Solver Algorithm for Two-Dimensional Grids with Block Diagonal Structure of the Matrix. Multi-Frontal Direct Solver Algorithm for Three-Dimensional Grids with Block Diagonal Structure of the Matrix. Multi-Frontal Direct Solver Algorithm for Two-Dimensional Isogeometric Finite Element Method. Expressing Partial LU Factorization by BLAS Calls. Multi-Frontal Solver Algorithm for Arbitrary Mesh-Based Computations. Elimination Trees. Reutilization and Reuse of Partial LU Factorizatons. Numerical Experiments.