lu_fact_2 Subroutine

  1. lu_implementation.F90
  2. lu_implementation
  3. lu_fact_2

subroutine lu_fact_2(a, ipiv, info)

Uses

  • proc~~lu_fact_2~~UsesGraph proc~lu_fact_2 lu_fact_2 module~class_psblas class_psblas proc~lu_fact_2->module~class_psblas module~class_stopwatch class_stopwatch module~class_psblas->module~class_stopwatch module~tools_psblas tools_psblas module~class_psblas->module~tools_psblas module~class_stopwatch->module~tools_psblas psb_base_mod psb_base_mod module~class_stopwatch->psb_base_mod psb_prec_mod psb_prec_mod module~tools_psblas->psb_prec_mod module~tools_psblas->psb_base_mod psb_krylov_mod psb_krylov_mod module~tools_psblas->psb_krylov_mod

Arguments

Type IntentOptional AttributesName
real(kind=psb_dpk_), intent(inout) :: a(2,2)
integer, intent(out) :: ipiv(2)
integer, intent(out) :: info

Called by

proc~~lu_fact_2~~CalledByGraph proc~lu_fact_2 lu_fact_2 proc~lu_fact lu_fact proc~lu_fact->proc~lu_fact_2 interface~lu_fact lu_fact interface~lu_fact->proc~lu_fact interface~factorize factorize interface~factorize->interface~lu_fact proc~alloc_plane alloc_plane proc~alloc_plane->interface~factorize interface~alloc_plane alloc_plane interface~alloc_plane->proc~alloc_plane proc~alloc_surface alloc_surface proc~alloc_surface->interface~alloc_plane interface~alloc_surface alloc_surface interface~alloc_surface->proc~alloc_surface

Contents

Source Code

lu_fact_2

Source Code

    SUBROUTINE  lu_fact_2(a,ipiv,info)
        USE class_psblas, ONLY : psb_dpk_
        REAL(psb_dpk_), INTENT(INOUT) :: A(2,2)
        INTEGER, INTENT(OUT) :: ipiv(2)
        INTEGER, INTENT(OUT) :: info
        !
        REAL(psb_dpk_) ::tmp, swp(2)
        INTEGER :: j, k, jp
        REAL(psb_dpk_), PARAMETER :: tol = 1.d-20
        info = 0

        IF (.FALSE.) THEN
            DO j = 1, 2
                jp = j - 1 + MAXLOC(ABS(a(j:,j)),dim=1)
                ipiv(j) = jp
                IF (jp /= j) THEN
                    DO k=1,2
                        tmp     = a(j,k)
                        a(j,k)  = a(jp,k)
                        a(jp,k) = tmp
                    END DO
                END IF

                IF(ABS(a(j,j)) < tol) THEN
                    info = j
                ELSE
                    a(j+1:,j) = a(j+1:,j) * (1.d0/a(j,j))
                END IF


                DO k = j + 1, 2
                    a(j+1:,k) = a(j+1:,k) - a(j,k) * a(j+1:,j)
                END DO

            END DO

        ELSE

            jp = 1 - 1 + MAXLOC(ABS(a(1:,1)),dim=1)
            ipiv(1) = jp
            IF (jp /= 1) THEN
                swp(1:2) = a(1,1:2)
                a(1,1:2) = a(jp,1:2)
                a(jp,1:2) = swp(1:2)
            END IF

            IF(ABS(a(1,1)) < tol) THEN
                info = 1
            ELSE
                a(1+1:,1) = a(1+1:,1) * (1.d0/a(1,1))
            END IF

            DO k = 1 + 1, 2
                a(1+1:,k) = a(1+1:,k) - a(1,k) * a(1+1:,1)
            END DO

            ipiv(2) = 2

            IF(ABS(a(2,2)) < tol) THEN
                info = 2
            END IF

        ENDIF
    END SUBROUTINE lu_fact_2