| [2759] | 1 | !CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC |
|---|
| 2 | ! |
|---|
| 3 | ! FFTPACK 5.0 |
|---|
| 4 | ! Copyright (C) 1995-2004, Scientific Computing Division, |
|---|
| 5 | ! University Corporation for Atmospheric Research |
|---|
| 6 | ! Licensed under the GNU General Public License (GPL) |
|---|
| 7 | ! |
|---|
| 8 | ! Authors: Paul N. Swarztrauber and Richard A. Valent |
|---|
| 9 | ! |
|---|
| 10 | ! $Id: costf1.f,v 1.2 2004/06/15 21:14:57 rodney Exp $ |
|---|
| 11 | ! |
|---|
| 12 | !CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC |
|---|
| 13 | |
|---|
| 14 | SUBROUTINE COSTF1(N,INC,X,WSAVE,WORK,IER) |
|---|
| 15 | REAL X(INC,*) ,WSAVE(*) |
|---|
| 16 | DOUBLE PRECISION DSUM |
|---|
| 17 | IER = 0 |
|---|
| 18 | NM1 = N-1 |
|---|
| 19 | NP1 = N+1 |
|---|
| 20 | NS2 = N/2 |
|---|
| 21 | IF (N-2) 200,101,102 |
|---|
| 22 | 101 X1H = X(1,1)+X(1,2) |
|---|
| 23 | X(1,2) = .5*(X(1,1)-X(1,2)) |
|---|
| 24 | X(1,1) = .5*X1H |
|---|
| 25 | GO TO 200 |
|---|
| 26 | 102 IF (N .GT. 3) GO TO 103 |
|---|
| 27 | X1P3 = X(1,1)+X(1,3) |
|---|
| 28 | TX2 = X(1,2)+X(1,2) |
|---|
| 29 | X(1,2) = .5*(X(1,1)-X(1,3)) |
|---|
| 30 | X(1,1) = .25*(X1P3+TX2) |
|---|
| 31 | X(1,3) = .25*(X1P3-TX2) |
|---|
| 32 | GO TO 200 |
|---|
| 33 | 103 DSUM = X(1,1)-X(1,N) |
|---|
| 34 | X(1,1) = X(1,1)+X(1,N) |
|---|
| 35 | DO 104 K=2,NS2 |
|---|
| 36 | KC = NP1-K |
|---|
| 37 | T1 = X(1,K)+X(1,KC) |
|---|
| 38 | T2 = X(1,K)-X(1,KC) |
|---|
| 39 | DSUM = DSUM+WSAVE(KC)*T2 |
|---|
| 40 | T2 = WSAVE(K)*T2 |
|---|
| 41 | X(1,K) = T1-T2 |
|---|
| 42 | X(1,KC) = T1+T2 |
|---|
| 43 | 104 END DO |
|---|
| 44 | MODN = MOD(N,2) |
|---|
| 45 | IF (MODN .EQ. 0) GO TO 124 |
|---|
| 46 | X(1,NS2+1) = X(1,NS2+1)+X(1,NS2+1) |
|---|
| 47 | 124 LENX = INC*(NM1-1) + 1 |
|---|
| 48 | LNSV = NM1 + INT(LOG(REAL(NM1))) + 4 |
|---|
| 49 | LNWK = NM1 |
|---|
| 50 | ! |
|---|
| 51 | CALL RFFT1F(NM1,INC,X,LENX,WSAVE(N+1),LNSV,WORK, & |
|---|
| 52 | & LNWK,IER1) |
|---|
| 53 | IF (IER1 .NE. 0) THEN |
|---|
| 54 | IER = 20 |
|---|
| 55 | CALL XERFFT ('COSTF1',-5) |
|---|
| 56 | GO TO 200 |
|---|
| 57 | ENDIF |
|---|
| 58 | ! |
|---|
| 59 | SNM1 = 1./FLOAT(NM1) |
|---|
| 60 | DSUM = SNM1*DSUM |
|---|
| 61 | IF(MOD(NM1,2) .NE. 0) GO TO 30 |
|---|
| 62 | X(1,NM1) = X(1,NM1)+X(1,NM1) |
|---|
| 63 | 30 DO 105 I=3,N,2 |
|---|
| 64 | XI = .5*X(1,I) |
|---|
| 65 | X(1,I) = .5*X(1,I-1) |
|---|
| 66 | X(1,I-1) = DSUM |
|---|
| 67 | DSUM = DSUM+XI |
|---|
| 68 | 105 END DO |
|---|
| 69 | IF (MODN .NE. 0) GO TO 117 |
|---|
| 70 | X(1,N) = DSUM |
|---|
| 71 | 117 X(1,1) = .5*X(1,1) |
|---|
| 72 | X(1,N) = .5*X(1,N) |
|---|
| 73 | 200 RETURN |
|---|
| 74 | END |
|---|
