ITERATE Subroutine

public subroutine ITERATE(ResultX, Tol, X0, Y0, X1, Y1, Iter, Cnvg)

Uses:
DataPrecisionGlobals

Arguments

Type	Intent		Name
real(kind=r64),	intent(out)	::	ResultX
real(kind=r64),	intent(in)	::	Tol
real(kind=r64),	intent(inout)	::	X0
real(kind=r64),	intent(inout)	::	Y0
real(kind=r64),	intent(inout)	::	X1
real(kind=r64),	intent(inout)	::	Y1
integer,	intent(in)	::	Iter
integer,	intent(out)	::	Cnvg

Source Code

ITERATE

Source Code

SUBROUTINE ITERATE(ResultX,Tol,X0,Y0,X1,Y1,Iter,Cnvg)

          ! SUBROUTINE INFORMATION:
          !       AUTHOR         Richard Liesen
          !       DATE WRITTEN   March 2004
          !       MODIFIED       na
          !       RE-ENGINEERED  na

          ! PURPOSE OF THIS SUBROUTINE:
          ! Iterately solves for the value of X which satisfies Y(X)=0.
          ! The subroutine tests for convergence and provides a new guess for the value of the
          ! independent variable X.

          ! METHODOLOGY EMPLOYED:
          ! na

          ! REFERENCES:
          ! Linear Correction based on the RegulaFalsi routine in EnergyPlus

          ! USE STATEMENTS:
  USE DataPrecisionGlobals
!unused0909  use dataglobals, only: outputfiledebug

  IMPLICIT NONE    ! Enforce explicit typing of all variables in this routine

          ! SUBROUTINE ARGUMENT DEFINITIONS:
  REAL(r64), INTENT(Out)   :: ResultX     !ResultX is the final Iteration result passed back to the calling routine
  REAL(r64), INTENT(In)    :: Tol         !Tolerance for Convergence
  REAL(r64), INTENT(InOut) :: X0          !Current value of X
  REAL(r64), INTENT(InOut) :: Y0          !Current value of the function Y(X)
  REAL(r64), INTENT(InOut) :: X1          !First Previous values of X
  REAL(r64), INTENT(InOut) :: Y1          !First Previous values of Y(X1)

  Integer, Intent(In) :: Iter        !Number of iterations
  Integer, Intent(Out):: Cnvg        !Convergence flag  Cnvg = 0:  Not converged
                                     !                  Cnvg = 1:  Converged

          ! SUBROUTINE PARAMETER DEFINITIONS:
  REAL(r64), PARAMETER :: small  = 1.d-9 !Small Number used to approximate zero
  REAL(r64), PARAMETER :: Perturb=0.1d0  !Perturbation applied to X to initialize iteration

          ! INTERFACE BLOCK SPECIFICATIONS
          ! na

          ! DERIVED TYPE DEFINITIONS
          ! na

          ! SUBROUTINE LOCAL VARIABLE DECLARATIONS:

  REAL(r64) :: Dy                         !Linear fit result

          ! FLOW:

          ! Check for convergence by comparing change in X
      IF (Iter .ne. 1) THEN
        IF (ABS(X0-X1) .LT. Tol .OR. Y0 .EQ. 0.0d0) THEN
          ResultX = X0
          Cnvg=1
          RETURN
        ENDIF
      ENDIF

          ! Not converged.
      Cnvg=0
      IF (Iter .EQ. 1) THEN

          ! New guess is specified by Perturb
        IF (ABS(X0) .GT. small) THEN
          ResultX = X0*(1.0d0+Perturb)
        ELSE
          ResultX = Perturb
        ENDIF

      ELSE

         ! New guess calculated from LINEAR FIT of most recent two points
         DY = Y0 - Y1
         IF (ABS(DY) < SMALL)    DY = SMALL
         ! new estimation

         ResultX = (Y0 * X1 - Y1 * X0 ) / DY

      ENDIF

        X1=X0
        Y1=Y0

      RETURN

END SUBROUTINE ITERATE

All Procedures

ITERATE Subroutine

Source Code

All Procedures

public subroutine ITERATE(ResultX, Tol, X0, Y0, X1, Y1, Iter, Cnvg)

Uses:

Arguments

Source Code

Source Code

All Procedures