share/fftpack5/fortran/sinq1b.f

   1 CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
   2 C
   3 C   FFTPACK 5.0
   4 C
   5 C   Authors:  Paul N. Swarztrauber and Richard A. Valent
   6 C
   7 C   $Id$
   8 C
   9 CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
  10
  11       SUBROUTINE SINQ1B ( N, INC, X, LENX, WSAVE, LENSAV,
  12      1                   WORK, LENWRK, IER)
  13       INTEGER    N, INC, LENX, LENSAV, LENWRK, IER
  14       REAL       X(INC,*), WSAVE(LENSAV), WORK(LENWRK)
  15 C
  16       IER = 0
  17 C
  18       IF (LENX .LT. INC*(N-1) + 1) THEN
  19         IER = 1
  20         CALL XERFFT ('SINQ1B', 6)
  21       ELSEIF (LENSAV .LT. 2*N + INT(LOG(REAL(N))/LOG(2.)) +4) THEN
  22         IER = 2
  23         CALL XERFFT ('SINQ1B', 8)
  24       ELSEIF (LENWRK .LT. N) THEN
  25         IER = 3
  26         CALL XERFFT ('SINQ1B', 10)
  27       ENDIF
  28 C
  29       IF (N .GT. 1) GO TO 101
  30       RETURN
  31   101 NS2 = N/2
  32       DO 102 K=2,N,2
  33          X(1,K) = -X(1,K)
  34   102 CONTINUE
  35       CALL COSQ1B (N,INC,X,LENX,WSAVE,LENSAV,WORK,LENWRK,IER1)
  36       IF (IER1 .NE. 0) THEN
  37         IER = 20
  38         CALL XERFFT ('SINQ1B',-5)
  39         GO TO 300
  40       ENDIF
  41       DO 103 K=1,NS2
  42          KC = N-K
  43          XHOLD = X(1,K)
  44          X(1,K) = X(1,KC+1)
  45          X(1,KC+1) = XHOLD
  46   103 CONTINUE
  47   300 RETURN
  48       END