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!
! Copyright (C) 2004-2006 Quantum ESPRESSO group
! This file is distributed under the terms of the
! GNU General Public License. See the file `License'
! in the root directory of the present distribution,
! or http://www.gnu.org/copyleft/gpl.txt .
!
!---------------------------------------------------------------------------
MODULE splinelib
!---------------------------------------------------------------------------
!
USE kinds, ONLY : DP
!
IMPLICIT NONE
!
PRIVATE
!
PUBLIC :: dosplineint, spline, splint, splint_deriv
!
INTERFACE dosplineint
!
MODULE PROCEDURE dosplineint_1D, dosplineint_2D
!
END INTERFACE
!
CONTAINS
!
!------------------------------------------------------------------------
SUBROUTINE spline( xdata, ydata, startu, startd, d2y )
!------------------------------------------------------------------------
!
IMPLICIT NONE
!
REAL(DP), INTENT(IN) :: xdata(:), ydata(:), startu, startd
REAL(DP), INTENT(OUT) :: d2y(:)
!
INTEGER :: i, k, ydim
REAL(DP) :: p, sig
REAL(DP), ALLOCATABLE :: u(:)
!
!
ydim = SIZE( ydata )
!
ALLOCATE( u( ydim ) )
!
u(1) = startu
d2y(1) = startd
!
DO i = 2, ydim - 1
!
sig = ( xdata(i) - xdata(i-1) ) / ( xdata(i+1) - xdata(i-1) )
p = sig * d2y(i- 1) + 2.0_DP
d2y(i) = ( sig - 1.0_DP ) / p
u(i) = ( 6.0_DP * ( ( ydata(i+1) - ydata(i) ) / &
( xdata(i+1) - xdata(i) ) - ( ydata(i) - ydata(i-1) ) / &
( xdata(i) - xdata(i-1) ) ) / &
( xdata(i+1) - xdata(i-1) ) - sig * u(i-1) ) / p
!
END DO
!
d2y(ydim) = 0
!
DO k = ydim - 1, 1, -1
!
d2y(k) = d2y(k) * d2y(k+1) + u(k)
!
END DO
!
DEALLOCATE( u )
!
END SUBROUTINE spline
!
!------------------------------------------------------------------------
FUNCTION splint( xdata, ydata, d2y, x )
!------------------------------------------------------------------------
!
IMPLICIT NONE
!
REAL(DP), INTENT(IN) :: xdata(:), ydata(:), d2y(:)
REAL(DP), INTENT(IN) :: x
!
REAL(DP) :: splint
INTEGER :: khi, klo, xdim
REAL(DP) :: a, b, h
!
!
xdim = SIZE( xdata )
!
klo = 1
khi = xdim
!
klo = MAX( MIN( locate( xdata, x ), ( xdim - 1 ) ), 1 )
!
khi = klo + 1
!
h = xdata(khi) - xdata(klo)
!
a = ( xdata(khi) - x ) / h
b = ( x - xdata(klo) ) / h
!
splint = a * ydata(klo) + b * ydata(khi) + &
( ( a**3 - a ) * d2y(klo) + ( b**3 - b ) * d2y(khi) ) * &
( h**2 ) / 6.0_DP
END FUNCTION splint
!------------------------------------------------------------------------
FUNCTION splint_deriv( xdata, ydata, d2y, x )
!------------------------------------------------------------------------
!
IMPLICIT NONE
!
REAL(DP), INTENT(IN) :: xdata(:), ydata(:), d2y(:)
REAL(DP), INTENT(IN) :: x
!
REAL(DP) :: splint_deriv
INTEGER :: khi, klo, xdim
REAL(DP) :: a, b, da, db, h
!
!
xdim = SIZE( xdata )
!
klo = 1
khi = xdim
!
klo = MAX( MIN( locate( xdata, x ), ( xdim - 1 ) ), 1 )
!
khi = klo + 1
!
h = xdata(khi) - xdata(klo)
!
a = ( xdata(khi) - x ) / h
b = ( x - xdata(klo) ) / h
da = -1.0_DP / h
db = 1.0_DP / h
!
splint_deriv = da * ydata(klo) + db * ydata(khi) + &
( ( 3.0_DP*a**2 - 1.0_DP ) * da * d2y(klo) + &
( 3.0_DP*b**2 - 1.0_DP ) * db * d2y(khi) ) * &
( h**2 ) / 6.0_DP
END FUNCTION splint_deriv
!-------------------------------------------------------------------
FUNCTION locate( xx, x )
!-------------------------------------------------------------------
!
IMPLICIT NONE
!
REAL(DP), INTENT(IN) :: xx(:)
REAL(DP), INTENT(IN) :: x
!
INTEGER :: locate
INTEGER :: n, jl, jm, ju
LOGICAL :: ascnd
!
!
n = SIZE( xx )
ascnd = ( xx(n) >= xx(1) )
jl = 0
ju = n + 1
!
main_loop: DO
!
IF ( ( ju - jl ) <= 1 ) EXIT main_loop
!
jm = ( ju + jl ) / 2
!
IF ( ascnd .EQV. ( x >= xx(jm) ) ) THEN
!
jl = jm
!
ELSE
!
ju = jm
!
END IF
!
END DO main_loop
!
IF ( x == xx(1) ) THEN
!
locate = 1
!
ELSE IF ( x == xx(n) ) THEN
!
locate = n - 1
!
ELSE
!
locate = jl
!
END IF
!
END FUNCTION locate
!
!
!------------------------------------------------------------------------
SUBROUTINE dosplineint_1D( old_mesh, old_vec, new_mesh, new_vec )
!------------------------------------------------------------------------
!
IMPLICIT NONE
!
REAL (DP), INTENT(IN) :: old_mesh(:), new_mesh(:)
REAL (DP), INTENT(IN) :: old_vec(:)
REAL (DP), INTENT(OUT) :: new_vec(:)
!
REAL (DP), ALLOCATABLE :: d2y(:)
INTEGER :: i
INTEGER :: old_dim, new_dim
!
!
old_dim = SIZE( old_vec )
new_dim = SIZE( new_vec )
!
IF ( old_dim /= SIZE( old_mesh ) ) &
CALL errore( 'dosplineint', &
'dimensions of old_mesh and old_vec do not match', 1 )
!
IF ( new_dim /= SIZE( new_mesh ) ) &
CALL errore( 'dosplineint', &
'dimensions of new_mesh and new_vec do not match', 1 )
!
ALLOCATE( d2y( old_dim ) )
!
d2y = 0
!
CALL spline( old_mesh , old_vec(:), 0.0_DP, 0.0_DP, d2y )
!
DO i = 1, new_dim
!
new_vec(i) = splint( old_mesh, old_vec(:), d2y, new_mesh(i) )
!
END DO
!
DEALLOCATE( d2y )
!
END SUBROUTINE dosplineint_1D
!
!------------------------------------------------------------------------
SUBROUTINE dosplineint_2D( old_mesh, old_vec, new_mesh, new_vec )
!------------------------------------------------------------------------
!
IMPLICIT NONE
!
REAL (DP), INTENT(IN) :: old_mesh(:), new_mesh(:)
REAL (DP), INTENT(IN) :: old_vec(:,:)
REAL (DP), INTENT(OUT) :: new_vec(:,:)
!
REAL (DP), ALLOCATABLE :: d2y(:)
INTEGER :: dim, i, j
INTEGER :: old_dim, new_dim
!
!
dim = SIZE( old_vec, 1 )
!
IF( dim /= SIZE( new_vec, 1 ) ) &
CALL errore( 'dosplineint', &
'dimensions of old_vec and new_vec do not match', 1 )
!
old_dim = SIZE( old_vec, 2 )
new_dim = SIZE( new_vec, 2 )
!
IF ( old_dim /= SIZE( old_mesh, 1 ) ) &
CALL errore( 'dosplineint', &
'dimensions of old_mesh and old_vec do not match', 1 )
!
IF ( new_dim /= SIZE( new_mesh, 1 ) ) &
CALL errore( 'dosplineint', &
'dimensions of new_mesh and new_vec do not match', 1 )
!
ALLOCATE( d2y( old_dim ) )
!
DO i = 1, dim
!
d2y = 0
!
CALL spline( old_mesh , old_vec(i,:), 0.0_DP, 0.0_DP, d2y )
!
DO j = 1, new_dim
!
new_vec(i,j) = splint( old_mesh, old_vec(i,:), d2y, new_mesh(j) )
!
END DO
!
END DO
!
DEALLOCATE( d2y )
!
END SUBROUTINE dosplineint_2D
!
END MODULE splinelib
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