share/fftpack5/fortran/cosq1b.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 COSQ1B (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 ('COSQ1B', 6)
  21         GO TO 300
  22       ELSEIF (LENSAV .LT. 2*N + INT(LOG(REAL(N))/LOG(2.)) +4) THEN
  23         IER = 2
  24         CALL XERFFT ('COSQ1B', 8)
  25         GO TO 300
  26       ELSEIF (LENWRK .LT. N) THEN
  27         IER = 3
  28         CALL XERFFT ('COSQ1B', 10)
  29         GO TO 300
  30       ENDIF
  31 C
  32       IF (N-2) 300,102,103
  33  102  SSQRT2 = 1./SQRT(2.)
  34       X1 = X(1,1)+X(1,2)
  35       X(1,2) = SSQRT2*(X(1,1)-X(1,2))
  36       X(1,1) = X1
  37       RETURN
  38   103 CALL COSQB1 (N,INC,X,WSAVE,WORK,IER1)
  39       IF (IER1 .NE. 0) THEN
  40         IER = 20
  41         CALL XERFFT ('COSQ1B',-5)
  42       ENDIF
  43 C
  44   300 RETURN
  45       END