dvsol Subroutine

private subroutine dvsol(me, wm, iwm, x, iersl)

This routine manages the solution of the linear system arising from a chord iteration. it is called if miter /= 0:

  • if miter is 1 or 2, it calls dgesl to accomplish this.
  • if miter = 3 it updates the coefficient h*rl1 in the diagonal matrix, and then computes the solution.
  • if miter is 4 or 5, it calls dgbsl.

Type Bound

dvode_t

Arguments

Type IntentOptional Attributes Name
class(dvode_t), intent(inout) :: me
real(kind=wp), intent(inout) :: wm(*)

real work space containing the inverse diagonal matrix if miter = 3 and the lu decomposition of the matrix otherwise. storage of matrix elements starts at wm(3). wm also contains the following matrix-related data: wm(1) = sqrt(uround) (not used here), wm(2) = hrl1, the previous value of h*rl1, used if miter = 3.
integer :: iwm(*)

integer work space containing pivot information, starting at iwm(31), if miter is 1, 2, 4, or 5. iwm also contains band parameters ml = iwm(1) and mu = iwm(2) if miter is 4 or 5.
real(kind=wp), intent(inout) :: x(*)

the right-hand side vector on input, and the solution vector on output, of length n.
integer, intent(out) :: iersl

output flag. iersl = 0 if no trouble occurred. iersl = 1 if a singular matrix arose with miter = 3.

Calls

proc~~dvsol~~CallsGraph proc~dvsol dvode_module::dvode_t%dvsol proc~dgbsl dvode_linpack_module::dgbsl proc~dvsol->proc~dgbsl proc~dgesl dvode_linpack_module::dgesl proc~dvsol->proc~dgesl proc~daxpy dvode_blas_module::daxpy proc~dgbsl->proc~daxpy proc~ddot dvode_blas_module::ddot proc~dgbsl->proc~ddot proc~dgesl->proc~daxpy proc~dgesl->proc~ddot

Called by

proc~~dvsol~~CalledByGraph proc~dvsol dvode_module::dvode_t%dvsol proc~dvnlsd dvode_module::dvode_t%dvnlsd proc~dvnlsd->proc~dvsol proc~dvstep dvode_module::dvode_t%dvstep proc~dvstep->proc~dvnlsd proc~dvode dvode_module::dvode_t%dvode proc~dvode->proc~dvstep

Source Code

   subroutine dvsol(me,wm,iwm,x,iersl)

      class(dvode_t),intent(inout) :: me
      real(wp),intent(inout) :: wm(*) !! real work space containing the inverse diagonal matrix if
                                      !! miter = 3 and the lu decomposition of the matrix otherwise.
                                      !! storage of matrix elements starts at wm(3).
                                      !! wm also contains the following matrix-related data:
                                      !! wm(1) = sqrt(uround) (not used here),
                                      !! wm(2) = hrl1, the previous value of h*rl1, used if miter = 3.
      real(wp),intent(inout) :: x(*) !! the right-hand side vector on input,
                                     !! and the solution vector
                                     !! on output, of length n.
      integer :: iwm(*) !! integer work space containing pivot information, starting at
                        !! iwm(31), if miter is 1, 2, 4, or 5.  iwm also contains band
                        !! parameters ml = iwm(1) and mu = iwm(2) if miter is 4 or 5.
      integer,intent(out) :: iersl !! output flag.  iersl = 0 if no trouble occurred.
                                   !! iersl = 1 if a singular matrix arose with miter = 3.

      integer :: i , meband , ml , mu
      real(wp) :: di , hrl1 , phrl1 , r

      real(wp),parameter :: one = 1.0_wp

      iersl = 0
      select case (me%dat%miter)
      case (3)
         phrl1 = wm(2)
         hrl1 = me%dat%h*me%dat%rl1
         wm(2) = hrl1
         if ( hrl1/=phrl1 ) then
            r = hrl1/phrl1
            do i = 1 , me%dat%n
               di = one - r*(one-one/wm(i+2))
               if ( abs(di)==zero ) then
                  iersl = 1
                  return
               end if
               wm(i+2) = one/di
            enddo
         endif
         do i = 1 , me%dat%n
            x(i) = wm(i+2)*x(i)
         enddo
      case (4,5)
         ml = iwm(1)
         mu = iwm(2)
         meband = 2*ml + mu + 1
         call dgbsl(wm(3),meband,me%dat%n,ml,mu,iwm(31),x,0)
      case default
         call dgesl(wm(3),me%dat%n,me%dat%n,iwm(31),x,0)
      end select

   end subroutine dvsol