| [2759] | 1 | !CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC |
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| 2 | ! |
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| 3 | ! FFTPACK 5.0 |
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| 4 | ! Copyright (C) 1995-2004, Scientific Computing Division, |
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| 5 | ! University Corporation for Atmospheric Research |
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| 6 | ! Licensed under the GNU General Public License (GPL) |
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| 7 | ! |
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| 8 | ! Authors: Paul N. Swarztrauber and Richard A. Valent |
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| 9 | ! |
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| 10 | ! $Id: cosqb1.f,v 1.2 2004/06/15 21:14:57 rodney Exp $ |
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| 11 | ! |
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| 12 | !CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC |
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| 13 | |
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| 14 | SUBROUTINE COSQB1 (N,INC,X,WSAVE,WORK,IER) |
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| 15 | DIMENSION X(INC,*) ,WSAVE(*) ,WORK(*) |
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| 16 | IER = 0 |
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| 17 | NS2 = (N+1)/2 |
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| 18 | NP2 = N+2 |
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| 19 | DO 101 I=3,N,2 |
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| 20 | XIM1 = X(1,I-1)+X(1,I) |
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| 21 | X(1,I) = .5*(X(1,I-1)-X(1,I)) |
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| 22 | X(1,I-1) = .5*XIM1 |
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| 23 | 101 END DO |
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| 24 | X(1,1) = .5*X(1,1) |
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| 25 | MODN = MOD(N,2) |
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| 26 | IF (MODN .NE. 0) GO TO 302 |
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| 27 | X(1,N) = .5*X(1,N) |
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| 28 | 302 LENX = INC*(N-1) + 1 |
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| 29 | LNSV = N + INT(LOG(REAL(N))) + 4 |
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| 30 | LNWK = N |
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| 31 | ! |
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| 32 | CALL RFFT1B(N,INC,X,LENX,WSAVE(N+1),LNSV,WORK,LNWK,IER1) |
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| 33 | IF (IER1 .NE. 0) THEN |
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| 34 | IER = 20 |
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| 35 | CALL XERFFT ('COSQB1',-5) |
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| 36 | GO TO 400 |
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| 37 | ENDIF |
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| 38 | ! |
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| 39 | DO 102 K=2,NS2 |
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| 40 | KC = NP2-K |
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| 41 | WORK(K) = WSAVE(K-1)*X(1,KC)+WSAVE(KC-1)*X(1,K) |
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| 42 | WORK(KC) = WSAVE(K-1)*X(1,K)-WSAVE(KC-1)*X(1,KC) |
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| 43 | 102 END DO |
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| 44 | IF (MODN .NE. 0) GO TO 305 |
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| 45 | X(1,NS2+1) = WSAVE(NS2)*(X(1,NS2+1)+X(1,NS2+1)) |
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| 46 | 305 DO 103 K=2,NS2 |
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| 47 | KC = NP2-K |
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| 48 | X(1,K) = WORK(K)+WORK(KC) |
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| 49 | X(1,KC) = WORK(K)-WORK(KC) |
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| 50 | 103 END DO |
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| 51 | X(1,1) = X(1,1)+X(1,1) |
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| 52 | 400 RETURN |
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| 53 | END |
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