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SUBROUTINE FIBIC2 (N,M,A,X,Y,XU,YU,XO,YO,VALUE,IERR)
C
C*****************************************************************
C *
C The subroutine determines a double integral of a spline *
C function over a rectangle [XU, XO] x [YU, YO]. *
C *
C----------------------------------------------------------------*
C *
C subroutines required: XYINTV, FIBIC1 *
C *
C*****************************************************************
C *
C author : Eberhard Heyne *
C date : 02.15.1983 *
C source : FORTRAN 77 *
C *
C*****************************************************************
C
IMPLICIT DOUBLE PRECISION (A-H,O-Z)
C
PARAMETER (KDIM=3,LDIM=3)
C
DIMENSION A(0:N,0:M,0:KDIM,0:LDIM),X(0:N),Y(0:M)
C
C* determine intervals and relative coordinates
C
CALL XYINTV(N,M,X,Y,IU,JU,XIU,ETAU,XU,YU,JERR)
IERR=JERR
IF(JERR .NE. 0) RETURN
CALL XYINTV(N,M,X,Y,IO,JO,XIO,ETAO,XO,YO,JERR)
IERR=JERR+1
IF(JERR .NE. 0) RETURN
FACTOR=1.0D0
IF(IU .GT. IO) THEN
I=IO
IO=IU
IU=I
XI=XIO
XIO=XIU
XIU=XI
FACTOR=-FACTOR
ENDIF
IF(JU .GT. JO) THEN
J=JO
JO=JU
JU=J
ETA=ETAO
ETAO=ETAU
ETAU=ETA
FACTOR=-FACTOR
ENDIF
S=FIBIC1(N,M,A,IU,JU,XIU,ETAU)
S=S-FIBIC1(N,M,A,IU,JO,XIU,ETAO)
S=S-FIBIC1(N,M,A,IO,JU,XIO,ETAU)
S=S+FIBIC1(N,M,A,IO,JO,XIO,ETAO)
DO 101 I=IU,IO-1
S=S+FIBIC1(N,M,A,I,JO,X(I+1)-X(I),ETAO)
S=S-FIBIC1(N,M,A,I,JU,X(I+1)-X(I),ETAU)
101 CONTINUE
DO 103 J=JU,JO-1
S=S+FIBIC1(N,M,A,IO,J,XIO,Y(J+1)-Y(J))
S=S-FIBIC1(N,M,A,IU,J,XIU,Y(J+1)-Y(J))
DO 102 I=IU,IO-1
S=S+FIBIC1(N,M,A,I,J,X(I+1)-X(I),Y(J+1)-Y(J))
102 CONTINUE
103 CONTINUE
IERR=0
VALUE=FACTOR*S
RETURN
END
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Contents
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