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73 lines
2.2 KiB
Fortran
73 lines
2.2 KiB
Fortran
*DECK DFSPVD
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SUBROUTINE DFSPVD (T, K, X, ILEFT, VNIKX, NDERIV)
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C***BEGIN PROLOGUE DFSPVD
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C***SUBSIDIARY
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C***PURPOSE Subsidiary to DFC
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C***LIBRARY SLATEC
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C***TYPE DOUBLE PRECISION (BSPLVD-S, DFSPVD-D)
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C***AUTHOR (UNKNOWN)
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C***DESCRIPTION
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C
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C **** Double Precision Version of BSPLVD ****
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C Calculates value and deriv.s of all B-splines which do not vanish at X
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C
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C Fill VNIKX(J,IDERIV), J=IDERIV, ... ,K with nonzero values of
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C B-splines of order K+1-IDERIV , IDERIV=NDERIV, ... ,1, by repeated
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C calls to DFSPVN
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C
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C***SEE ALSO DFC
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C***ROUTINES CALLED DFSPVN
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C***REVISION HISTORY (YYMMDD)
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C 780801 DATE WRITTEN
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C 890531 Changed all specific intrinsics to generic. (WRB)
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C 890831 Modified array declarations. (WRB)
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C 890911 Removed unnecessary intrinsics. (WRB)
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C 891214 Prologue converted to Version 4.0 format. (BAB)
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C 900328 Added TYPE section. (WRB)
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C***END PROLOGUE DFSPVD
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IMPLICIT DOUBLE PRECISION (A-H,O-Z)
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DIMENSION T(*),VNIKX(K,*)
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DIMENSION A(20,20)
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C***FIRST EXECUTABLE STATEMENT DFSPVD
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CALL DFSPVN(T,K+1-NDERIV,1,X,ILEFT,VNIKX(NDERIV,NDERIV))
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IF (NDERIV .LE. 1) GO TO 99
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IDERIV = NDERIV
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DO 15 I=2,NDERIV
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IDERVM = IDERIV-1
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DO 11 J=IDERIV,K
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11 VNIKX(J-1,IDERVM) = VNIKX(J,IDERIV)
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IDERIV = IDERVM
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CALL DFSPVN(T,0,2,X,ILEFT,VNIKX(IDERIV,IDERIV))
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15 CONTINUE
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C
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DO 20 I=1,K
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DO 19 J=1,K
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19 A(I,J) = 0.D0
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20 A(I,I) = 1.D0
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KMD = K
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DO 40 M=2,NDERIV
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KMD = KMD-1
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FKMD = KMD
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I = ILEFT
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J = K
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21 JM1 = J-1
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IPKMD = I + KMD
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DIFF = T(IPKMD) - T(I)
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IF (JM1 .EQ. 0) GO TO 26
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IF (DIFF .EQ. 0.D0) GO TO 25
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DO 24 L=1,J
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24 A(L,J) = (A(L,J) - A(L,J-1))/DIFF*FKMD
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25 J = JM1
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I = I - 1
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GO TO 21
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26 IF (DIFF .EQ. 0.) GO TO 30
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A(1,1) = A(1,1)/DIFF*FKMD
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C
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30 DO 40 I=1,K
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V = 0.D0
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JLOW = MAX(I,M)
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DO 35 J=JLOW,K
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35 V = A(I,J)*VNIKX(J,M) + V
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40 VNIKX(I,M) = V
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99 RETURN
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END
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