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C $Header: /u/gcmpack/MITgcm/pkg/flt/flt_interp_linear.F,v 1.1 2009/02/01 21:10:51 jmc Exp $
C $Name: $
#include "FLT_OPTIONS.h"
C-- Contents
C-- o FLT_BILINEAR
C-- o FLT_TRILINEAR
C-- o FLT_BILINEAR2D
C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----|
SUBROUTINE FLT_BILINEAR(
I ix, jy,
O uu,
I var,
I kl, nu, bi, bj, myThid )
C ==================================================================
C SUBROUTINE FLT_BILINEAR
C ==================================================================
C o Bilinear scheme to interpolate variable to particle position
C given by its fractional (real) index ix,jy location
C ==================================================================
C !USES:
IMPLICIT NONE
C == global variables ==
#include "SIZE.h"
C == routine arguments ==
_RL ix, jy
_RL uu
_RL var(1-OLx:sNx+OLx,1-OLy:sNy+OLy,Nr,nSx,nSy)
INTEGER kl, nu, bi, bj, myThid
C == local variables ==
INTEGER i1, j1, i2, j2, klp
_RL ddx, ddy
_RL u11, u12, u22, u21
C == end of interface ==
C-- to choose the u box in which the particle is found
C nu=0 for T, S
C nu=1 for u
C nu=2 for v
C nu=3 for Vorticity
C nu=4 for w
IF ( kl.LT.1 .OR. kl.GT.Nr ) THEN
c WRITE(msgbuf,'(A,I8)')
c & ' FLT_BILINEAR: illegal value for kl=',kl
c CALL PRINT_ERROR( msgbuf, myThid )
STOP 'ABNORMAL END: S/R FLT_BILINEAR'
ENDIF
C-- find x-index according to grid-location of variable
IF ( MOD(nu,2).EQ.0 ) THEN
i1 = INT(ix)
ddx = ix - DFLOAT(i1)
ELSE
i1 = NINT(ix)
ddx = 0.5 _d 0 + ix - DFLOAT(i1)
ENDIF
C-- find y-index according to grid-location of variable
IF ( MOD(nu,4).LE.1 ) THEN
j1 = INT(jy)
ddy = jy - DFLOAT(j1)
ELSE
j1 = NINT(jy)
ddy = 0.5 _d 0 + jy - DFLOAT(j1)
ENDIF
C-- Set the higher index for interpolation
i2 = i1 + 1
j2 = j1 + 1
C-- No need to change start/end index : use array overlap if needed
C-- bilinear interpolation (from numerical recipes)
IF (nu.LE.3) THEN
uu = ( (1.-ddx)*(1.-ddy)*var(i1,j1,kl,bi,bj)
& + ddx * ddy *var(i2,j2,kl,bi,bj) )
& + ( ddx *(1.-ddy)*var(i2,j1,kl,bi,bj)
& + (1.-ddx)* ddy *var(i1,j2,kl,bi,bj) )
ELSE
klp = MIN(kl+1,Nr)
u11 = ( var(i1,j1,kl,bi,bj)+var(i1,j1,klp,bi,bj) )*0.5 _d 0
u21 = ( var(i2,j1,kl,bi,bj)+var(i2,j1,klp,bi,bj) )*0.5 _d 0
u22 = ( var(i2,j2,kl,bi,bj)+var(i2,j2,klp,bi,bj) )*0.5 _d 0
u12 = ( var(i1,j2,kl,bi,bj)+var(i1,j2,klp,bi,bj) )*0.5 _d 0
uu = ( (1.-ddx)*(1.-ddy)*u11
& + ddx * ddy *u22 )
& + ( ddx *(1.-ddy)*u21
& + (1.-ddx)* ddy *u12 )
ENDIF
RETURN
END
C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----|
SUBROUTINE FLT_TRILINEAR(
I ix, jy, kz,
O uu,
I var,
I nu, bi, bj, myThid )
C ==================================================================
C SUBROUTINE FLT_TRILINEAR
C ==================================================================
C o Trilinear scheme to interpolate variable to particle position
C given by its fractional (real) index ix,jy,kz location
C This routine is a straight forward generalization of the
C bilinear interpolation scheme.
C
C started: 2004.05.28 Antti Westerlund (antti.westerlund@fimr.fi)
C and Sergio Jaramillo (sju@eos.ubc.ca).
C (adopted from SUBROUTINE bilinear by Arne Biastoch)
C ==================================================================
C !USES:
IMPLICIT NONE
C == global variables ==
#include "SIZE.h"
C == routine arguments ==
_RL ix, jy, kz
_RL uu
_RL var(1-OLx:sNx+OLx,1-OLy:sNy+OLy,Nr,nSx,nSy)
INTEGER nu, bi, bj, myThid
C == local variables ==
INTEGER i1, j1, k1, i2, j2, k2
_RL ddx, ddy, ddz
C == end of interface ==
C to choose the u box in which the particle is found
C nu=0 for T, S
C nu=1 for u
C nu=2 for v
C nu=3 for Vorticity
C nu=4 for w
C-- find x-index according to grid-location of variable
IF ( MOD(nu,2).EQ.0 ) THEN
i1 = INT(ix)
ddx = ix - DFLOAT(i1)
ELSE
i1 = NINT(ix)
ddx = 0.5 _d 0 + ix - DFLOAT(i1)
ENDIF
C-- find y-index according to grid-location of variable
IF ( MOD(nu,4).LE.1 ) THEN
j1 = INT(jy)
ddy = jy - DFLOAT(j1)
ELSE
j1 = NINT(jy)
ddy = 0.5 _d 0 + jy - DFLOAT(j1)
ENDIF
C-- find z-index according to grid-location of variable
IF ( nu.LE.3 ) THEN
k1 = INT(kz)
ddz = kz - DFLOAT(k1)
ELSE
k1 = NINT(kz)
ddz = 0.5 _d 0 + kz - DFLOAT(k1)
ENDIF
C-- Set the higher index for interpolation
i2 = i1 + 1
j2 = j1 + 1
k2 = k1 + 1
C-- No need to change start/end horizontal index : use array overlap if needed
C-- Need to adjust start/end vertical index :
k1 = MIN( MAX( k1, 1 ), Nr )
k2 = MIN( MAX( k2, 1 ), Nr )
C Trilinear interpolation, a straight forward generalization
C of the bilinear interpolation scheme.
uu = (1.-ddz)*( ( (1.-ddx)*(1.-ddy)*var(i1,j1,k1,bi,bj)
& + ddx * ddy *var(i2,j2,k1,bi,bj) )
& + ( ddx *(1.-ddy)*var(i2,j1,k1,bi,bj)
& + (1.-ddx)* ddy *var(i1,j2,k1,bi,bj) ) )
& + ddz *( ( (1.-ddx)*(1.-ddy)*var(i1,j1,k2,bi,bj)
& + ddx * ddy *var(i2,j2,k2,bi,bj) )
& + ( ddx*(1.-ddy) *var(i2,j1,k2,bi,bj)
& + (1.-ddx)* ddy *var(i1,j2,k2,bi,bj) ) )
RETURN
END
C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----|
SUBROUTINE FLT_BILINEAR2D(
I ix, jy,
O uu,
I var,
I nu, bi, bj, myThid )
C ==================================================================
C SUBROUTINE FLT_BILINEAR2D
C ==================================================================
C o Bilinear scheme to interpolate 2-D variable to particle position
C given by its fractional (real) index ix,jy location
C
C started: Arne Biastoch abiastoch@ucsd.edu 13-Jan-2000
C (adopted from SUBROUTINE bilinear)
C ==================================================================
C !USES:
IMPLICIT NONE
C == global variables ==
#include "SIZE.h"
C == routine arguments ==
_RL ix, jy
_RL uu
_RL var(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy)
INTEGER nu, bi, bj, myThid
C == local variables ==
INTEGER i1, j1, i2, j2
_RL ddx, ddy
C == end of interface ==
C to choose the u box in which the particle is found
C nu=0 for T, S
C nu=1 for u
C nu=2 for v
C nu=3 for Vorticity
C nu=4 for w
C-- find x-index according to grid-location of variable
IF ( MOD(nu,2).EQ.0 ) THEN
i1 = INT(ix)
ddx = ix - DFLOAT(i1)
ELSE
i1 = NINT(ix)
ddx = 0.5 _d 0 + ix - DFLOAT(i1)
ENDIF
C-- find y-index according to grid-location of variable
IF ( MOD(nu,4).LE.1 ) THEN
j1 = INT(jy)
ddy = jy - DFLOAT(j1)
ELSE
j1 = NINT(jy)
ddy = 0.5 _d 0 + jy - DFLOAT(j1)
ENDIF
C-- Set the higher index for interpolation
i2 = i1 + 1
j2 = j1 + 1
C-- No need to change start/end index : use array overlap if needed
C bilinear interpolation (from numerical recipes)
uu = ( (1.-ddx)*(1.-ddy)*var(i1,j1,bi,bj)
& + ddx * ddy *var(i2,j2,bi,bj) )
& + ( ddx *(1.-ddy)*var(i2,j1,bi,bj)
& + (1.-ddx)* ddy *var(i1,j2,bi,bj) )
RETURN
END
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