website/archive/binaries/mac/src/disembl/Tisean_3.0.1/source_f/slatec/radf3.f

   1 *DECK RADF3
   2       SUBROUTINE RADF3 (IDO, L1, CC, CH, WA1, WA2)
   3 C***BEGIN PROLOGUE  RADF3
   4 C***SUBSIDIARY
   5 C***PURPOSE  Calculate the fast Fourier transform of subvectors of
   6 C            length three.
   7 C***LIBRARY   SLATEC (FFTPACK)
   8 C***TYPE      SINGLE PRECISION (RADF3-S)
   9 C***AUTHOR  Swarztrauber, P. N., (NCAR)
  10 C***ROUTINES CALLED  (NONE)
  11 C***REVISION HISTORY  (YYMMDD)
  12 C   790601  DATE WRITTEN
  13 C   830401  Modified to use SLATEC library source file format.
  14 C   860115  Modified by Ron Boisvert to adhere to Fortran 77 by
  15 C           (a) changing dummy array size declarations (1) to (*),
  16 C           (b) changing definition of variable TAUI by using
  17 C               FORTRAN intrinsic function SQRT instead of a DATA
  18 C               statement.
  19 C   881128  Modified by Dick Valent to meet prologue standards.
  20 C   890831  Modified array declarations.  (WRB)
  21 C   891214  Prologue converted to Version 4.0 format.  (BAB)
  22 C   900402  Added TYPE section.  (WRB)
  23 C***END PROLOGUE  RADF3
  24       DIMENSION CH(IDO,3,*), CC(IDO,L1,3), WA1(*), WA2(*)
  25 C***FIRST EXECUTABLE STATEMENT  RADF3
  26       TAUR = -.5
  27       TAUI = .5*SQRT(3.)
  28       DO 101 K=1,L1
  29          CR2 = CC(1,K,2)+CC(1,K,3)
  30          CH(1,1,K) = CC(1,K,1)+CR2
  31          CH(1,3,K) = TAUI*(CC(1,K,3)-CC(1,K,2))
  32          CH(IDO,2,K) = CC(1,K,1)+TAUR*CR2
  33   101 CONTINUE
  34       IF (IDO .EQ. 1) RETURN
  35       IDP2 = IDO+2
  36       IF((IDO-1)/2.LT.L1) GO TO 104
  37       DO 103 K=1,L1
  38 CDIR$ IVDEP
  39          DO 102 I=3,IDO,2
  40             IC = IDP2-I
  41             DR2 = WA1(I-2)*CC(I-1,K,2)+WA1(I-1)*CC(I,K,2)
  42             DI2 = WA1(I-2)*CC(I,K,2)-WA1(I-1)*CC(I-1,K,2)
  43             DR3 = WA2(I-2)*CC(I-1,K,3)+WA2(I-1)*CC(I,K,3)
  44             DI3 = WA2(I-2)*CC(I,K,3)-WA2(I-1)*CC(I-1,K,3)
  45             CR2 = DR2+DR3
  46             CI2 = DI2+DI3
  47             CH(I-1,1,K) = CC(I-1,K,1)+CR2
  48             CH(I,1,K) = CC(I,K,1)+CI2
  49             TR2 = CC(I-1,K,1)+TAUR*CR2
  50             TI2 = CC(I,K,1)+TAUR*CI2
  51             TR3 = TAUI*(DI2-DI3)
  52             TI3 = TAUI*(DR3-DR2)
  53             CH(I-1,3,K) = TR2+TR3
  54             CH(IC-1,2,K) = TR2-TR3
  55             CH(I,3,K) = TI2+TI3
  56             CH(IC,2,K) = TI3-TI2
  57   102    CONTINUE
  58   103 CONTINUE
  59       RETURN
  60   104 DO 106 I=3,IDO,2
  61          IC = IDP2-I
  62 CDIR$ IVDEP
  63          DO 105 K=1,L1
  64             DR2 = WA1(I-2)*CC(I-1,K,2)+WA1(I-1)*CC(I,K,2)
  65             DI2 = WA1(I-2)*CC(I,K,2)-WA1(I-1)*CC(I-1,K,2)
  66             DR3 = WA2(I-2)*CC(I-1,K,3)+WA2(I-1)*CC(I,K,3)
  67             DI3 = WA2(I-2)*CC(I,K,3)-WA2(I-1)*CC(I-1,K,3)
  68             CR2 = DR2+DR3
  69             CI2 = DI2+DI3
  70             CH(I-1,1,K) = CC(I-1,K,1)+CR2
  71             CH(I,1,K) = CC(I,K,1)+CI2
  72             TR2 = CC(I-1,K,1)+TAUR*CR2
  73             TI2 = CC(I,K,1)+TAUR*CI2
  74             TR3 = TAUI*(DI2-DI3)
  75             TI3 = TAUI*(DR3-DR2)
  76             CH(I-1,3,K) = TR2+TR3
  77             CH(IC-1,2,K) = TR2-TR3
  78             CH(I,3,K) = TI2+TI3
  79             CH(IC,2,K) = TI3-TI2
  80   105    CONTINUE
  81   106 CONTINUE
  82       RETURN
  83       END