| 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: costf1.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 COSTF1(N,INC,X,WSAVE,WORK,IER) |
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| 15 | REAL X(INC,*) ,WSAVE(*) |
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| 16 | DOUBLE PRECISION DSUM |
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| 17 | IER = 0 |
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| 18 | NM1 = N-1 |
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| 19 | NP1 = N+1 |
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| 20 | NS2 = N/2 |
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| 21 | IF (N-2) 200,101,102 |
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| 22 | 101 X1H = X(1,1)+X(1,2) |
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| 23 | X(1,2) = .5*(X(1,1)-X(1,2)) |
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| 24 | X(1,1) = .5*X1H |
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| 25 | GO TO 200 |
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| 26 | 102 IF (N .GT. 3) GO TO 103 |
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| 27 | X1P3 = X(1,1)+X(1,3) |
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| 28 | TX2 = X(1,2)+X(1,2) |
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| 29 | X(1,2) = .5*(X(1,1)-X(1,3)) |
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| 30 | X(1,1) = .25*(X1P3+TX2) |
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| 31 | X(1,3) = .25*(X1P3-TX2) |
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| 32 | GO TO 200 |
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| 33 | 103 DSUM = X(1,1)-X(1,N) |
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| 34 | X(1,1) = X(1,1)+X(1,N) |
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| 35 | DO 104 K=2,NS2 |
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| 36 | KC = NP1-K |
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| 37 | T1 = X(1,K)+X(1,KC) |
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| 38 | T2 = X(1,K)-X(1,KC) |
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| 39 | DSUM = DSUM+WSAVE(KC)*T2 |
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| 40 | T2 = WSAVE(K)*T2 |
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| 41 | X(1,K) = T1-T2 |
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| 42 | X(1,KC) = T1+T2 |
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| 43 | 104 END DO |
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| 44 | MODN = MOD(N,2) |
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| 45 | IF (MODN .EQ. 0) GO TO 124 |
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| 46 | X(1,NS2+1) = X(1,NS2+1)+X(1,NS2+1) |
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| 47 | 124 LENX = INC*(NM1-1) + 1 |
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| 48 | LNSV = NM1 + INT(LOG(REAL(NM1))) + 4 |
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| 49 | LNWK = NM1 |
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| 50 | ! |
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| 51 | CALL RFFT1F(NM1,INC,X,LENX,WSAVE(N+1),LNSV,WORK, & |
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| 52 | & LNWK,IER1) |
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| 53 | IF (IER1 .NE. 0) THEN |
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| 54 | IER = 20 |
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| 55 | CALL XERFFT ('COSTF1',-5) |
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| 56 | GO TO 200 |
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| 57 | ENDIF |
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| 58 | ! |
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| 59 | SNM1 = 1./FLOAT(NM1) |
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| 60 | DSUM = SNM1*DSUM |
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| 61 | IF(MOD(NM1,2) .NE. 0) GO TO 30 |
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| 62 | X(1,NM1) = X(1,NM1)+X(1,NM1) |
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| 63 | 30 DO 105 I=3,N,2 |
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| 64 | XI = .5*X(1,I) |
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| 65 | X(1,I) = .5*X(1,I-1) |
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| 66 | X(1,I-1) = DSUM |
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| 67 | DSUM = DSUM+XI |
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| 68 | 105 END DO |
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| 69 | IF (MODN .NE. 0) GO TO 117 |
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| 70 | X(1,N) = DSUM |
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| 71 | 117 X(1,1) = .5*X(1,1) |
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| 72 | X(1,N) = .5*X(1,N) |
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| 73 | 200 RETURN |
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| 74 | END |
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