share/fftpack5/fortran/cost1i.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 COST1I (N, WSAVE, LENSAV, IER)
  12       INTEGER    N, LENSAV, IER
  13       REAL       WSAVE(LENSAV)
  14 C
  15       IER = 0
  16 C
  17       IF (LENSAV .LT. 2*N + INT(LOG(REAL(N))/LOG(2.)) +4) THEN
  18         IER = 2
  19         CALL XERFFT ('COST1I', 3)
  20         GO TO 300
  21       ENDIF
  22 C
  23       IF (N .LE. 3) RETURN
  24       NM1 = N-1
  25       NP1 = N+1
  26       NS2 = N/2
  27       PI = 4.*ATAN(1.)
  28       DT = PI/FLOAT(NM1)
  29       FK = 0.
  30       DO 101 K=2,NS2
  31          KC = NP1-K
  32          FK = FK+1.
  33          WSAVE(K) = 2.*SIN(FK*DT)
  34          WSAVE(KC) = 2.*COS(FK*DT)
  35   101 CONTINUE
  36       LNSV = NM1 + INT(LOG(REAL(NM1))/LOG(2.)) +4
  37       CALL RFFT1I (NM1, WSAVE(N+1), LNSV, IER1)
  38       IF (IER1 .NE. 0) THEN
  39         IER = 20
  40         CALL XERFFT ('COST1I',-5)
  41       ENDIF
  42   300 CONTINUE
  43       RETURN
  44       END