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47 lines
1.4 KiB
Fortran
47 lines
1.4 KiB
Fortran
*DECK BSPLVN
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SUBROUTINE BSPLVN (T, JHIGH, INDEX, X, ILEFT, VNIKX)
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C***BEGIN PROLOGUE BSPLVN
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C***SUBSIDIARY
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C***PURPOSE Subsidiary to FC
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C***LIBRARY SLATEC
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C***TYPE SINGLE PRECISION (BSPLVN-S, DFSPVN-D)
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C***AUTHOR (UNKNOWN)
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C***DESCRIPTION
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C
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C Calculates the value of all possibly nonzero B-splines at *X* of
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C order MAX(JHIGH,(J+1)(INDEX-1)) on *T*.
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C
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C***SEE ALSO FC
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C***ROUTINES CALLED (NONE)
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C***REVISION HISTORY (YYMMDD)
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C 780801 DATE WRITTEN
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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 BSPLVN
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DIMENSION T(*),VNIKX(*)
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DIMENSION DELTAM(20),DELTAP(20)
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SAVE J, DELTAM, DELTAP
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DATA J/1/,(DELTAM(I),I=1,20),(DELTAP(I),I=1,20)/40*0./
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C***FIRST EXECUTABLE STATEMENT BSPLVN
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GO TO (10,20),INDEX
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10 J = 1
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VNIKX(1) = 1.
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IF (J .GE. JHIGH) GO TO 99
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C
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20 IPJ = ILEFT+J
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DELTAP(J) = T(IPJ) - X
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IMJP1 = ILEFT-J+1
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DELTAM(J) = X - T(IMJP1)
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VMPREV = 0.
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JP1 = J+1
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DO 26 L=1,J
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JP1ML = JP1-L
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VM = VNIKX(L)/(DELTAP(L) + DELTAM(JP1ML))
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VNIKX(L) = VM*DELTAP(L) + VMPREV
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26 VMPREV = VM*DELTAM(JP1ML)
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VNIKX(JP1) = VMPREV
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J = JP1
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IF (J .LT. JHIGH) GO TO 20
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C
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99 RETURN
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END
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