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53 lines
1.7 KiB
Fortran
53 lines
1.7 KiB
Fortran
*DECK DDNTP
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SUBROUTINE DDNTP (H, K, N, NQ, T, TOUT, YH, Y)
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C***BEGIN PROLOGUE DDNTP
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C***SUBSIDIARY
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C***PURPOSE Subroutine DDNTP interpolates the K-th derivative of Y at
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C TOUT, using the data in the YH array. If K has a value
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C greater than NQ, the NQ-th derivative is calculated.
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C***LIBRARY SLATEC (SDRIVE)
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C***TYPE DOUBLE PRECISION (SDNTP-S, DDNTP-D, CDNTP-C)
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C***AUTHOR Kahaner, D. K., (NIST)
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C National Institute of Standards and Technology
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C Gaithersburg, MD 20899
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C Sutherland, C. D., (LANL)
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C Mail Stop D466
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C Los Alamos National Laboratory
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C Los Alamos, NM 87545
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C***ROUTINES CALLED (NONE)
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C***REVISION HISTORY (YYMMDD)
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C 790601 DATE WRITTEN
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C 900329 Initial submission to SLATEC.
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C***END PROLOGUE DDNTP
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INTEGER I, J, JJ, K, KK, KUSED, N, NQ
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DOUBLE PRECISION FACTOR, H, R, T, TOUT, Y(*), YH(N,*)
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C***FIRST EXECUTABLE STATEMENT DDNTP
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IF (K .EQ. 0) THEN
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DO 10 I = 1,N
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10 Y(I) = YH(I,NQ+1)
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R = ((TOUT - T)/H)
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DO 20 JJ = 1,NQ
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J = NQ + 1 - JJ
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DO 20 I = 1,N
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20 Y(I) = YH(I,J) + R*Y(I)
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ELSE
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KUSED = MIN(K, NQ)
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FACTOR = 1.D0
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DO 40 KK = 1,KUSED
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40 FACTOR = FACTOR*(NQ+1-KK)
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DO 50 I = 1,N
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50 Y(I) = FACTOR*YH(I,NQ+1)
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R = ((TOUT - T)/H)
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DO 80 JJ = KUSED+1,NQ
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J = KUSED + 1 + NQ - JJ
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FACTOR = 1.D0
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DO 60 KK = 1,KUSED
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60 FACTOR = FACTOR*(J-KK)
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DO 70 I = 1,N
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70 Y(I) = FACTOR*YH(I,J) + R*Y(I)
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80 CONTINUE
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DO 100 I = 1,N
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100 Y(I) = Y(I)*H**(-KUSED)
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END IF
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RETURN
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END
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