website/archive/binaries/mac/src/disembl/Tisean_3.0.1/source_f/slatec/radb4.f

   1 *DECK RADB4
   2       SUBROUTINE RADB4 (IDO, L1, CC, CH, WA1, WA2, WA3)
   3 C***BEGIN PROLOGUE  RADB4
   4 C***SUBSIDIARY
   5 C***PURPOSE  Calculate the fast Fourier transform of subvectors of
   6 C            length four.
   7 C***LIBRARY   SLATEC (FFTPACK)
   8 C***TYPE      SINGLE PRECISION (RADB4-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 SQRT2 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  RADB4
  24       DIMENSION CC(IDO,4,*), CH(IDO,L1,4), WA1(*), WA2(*), WA3(*)
  25 C***FIRST EXECUTABLE STATEMENT  RADB4
  26       SQRT2 = SQRT(2.)
  27       DO 101 K=1,L1
  28          TR1 = CC(1,1,K)-CC(IDO,4,K)
  29          TR2 = CC(1,1,K)+CC(IDO,4,K)
  30          TR3 = CC(IDO,2,K)+CC(IDO,2,K)
  31          TR4 = CC(1,3,K)+CC(1,3,K)
  32          CH(1,K,1) = TR2+TR3
  33          CH(1,K,2) = TR1-TR4
  34          CH(1,K,3) = TR2-TR3
  35          CH(1,K,4) = TR1+TR4
  36   101 CONTINUE
  37       IF (IDO-2) 107,105,102
  38   102 IDP2 = IDO+2
  39       IF((IDO-1)/2.LT.L1) GO TO 108
  40       DO 104 K=1,L1
  41 CDIR$ IVDEP
  42          DO 103 I=3,IDO,2
  43             IC = IDP2-I
  44             TI1 = CC(I,1,K)+CC(IC,4,K)
  45             TI2 = CC(I,1,K)-CC(IC,4,K)
  46             TI3 = CC(I,3,K)-CC(IC,2,K)
  47             TR4 = CC(I,3,K)+CC(IC,2,K)
  48             TR1 = CC(I-1,1,K)-CC(IC-1,4,K)
  49             TR2 = CC(I-1,1,K)+CC(IC-1,4,K)
  50             TI4 = CC(I-1,3,K)-CC(IC-1,2,K)
  51             TR3 = CC(I-1,3,K)+CC(IC-1,2,K)
  52             CH(I-1,K,1) = TR2+TR3
  53             CR3 = TR2-TR3
  54             CH(I,K,1) = TI2+TI3
  55             CI3 = TI2-TI3
  56             CR2 = TR1-TR4
  57             CR4 = TR1+TR4
  58             CI2 = TI1+TI4
  59             CI4 = TI1-TI4
  60             CH(I-1,K,2) = WA1(I-2)*CR2-WA1(I-1)*CI2
  61             CH(I,K,2) = WA1(I-2)*CI2+WA1(I-1)*CR2
  62             CH(I-1,K,3) = WA2(I-2)*CR3-WA2(I-1)*CI3
  63             CH(I,K,3) = WA2(I-2)*CI3+WA2(I-1)*CR3
  64             CH(I-1,K,4) = WA3(I-2)*CR4-WA3(I-1)*CI4
  65             CH(I,K,4) = WA3(I-2)*CI4+WA3(I-1)*CR4
  66   103    CONTINUE
  67   104 CONTINUE
  68       GO TO 111
  69   108 DO 110 I=3,IDO,2
  70          IC = IDP2-I
  71 CDIR$ IVDEP
  72          DO 109 K=1,L1
  73             TI1 = CC(I,1,K)+CC(IC,4,K)
  74             TI2 = CC(I,1,K)-CC(IC,4,K)
  75             TI3 = CC(I,3,K)-CC(IC,2,K)
  76             TR4 = CC(I,3,K)+CC(IC,2,K)
  77             TR1 = CC(I-1,1,K)-CC(IC-1,4,K)
  78             TR2 = CC(I-1,1,K)+CC(IC-1,4,K)
  79             TI4 = CC(I-1,3,K)-CC(IC-1,2,K)
  80             TR3 = CC(I-1,3,K)+CC(IC-1,2,K)
  81             CH(I-1,K,1) = TR2+TR3
  82             CR3 = TR2-TR3
  83             CH(I,K,1) = TI2+TI3
  84             CI3 = TI2-TI3
  85             CR2 = TR1-TR4
  86             CR4 = TR1+TR4
  87             CI2 = TI1+TI4
  88             CI4 = TI1-TI4
  89             CH(I-1,K,2) = WA1(I-2)*CR2-WA1(I-1)*CI2
  90             CH(I,K,2) = WA1(I-2)*CI2+WA1(I-1)*CR2
  91             CH(I-1,K,3) = WA2(I-2)*CR3-WA2(I-1)*CI3
  92             CH(I,K,3) = WA2(I-2)*CI3+WA2(I-1)*CR3
  93             CH(I-1,K,4) = WA3(I-2)*CR4-WA3(I-1)*CI4
  94             CH(I,K,4) = WA3(I-2)*CI4+WA3(I-1)*CR4
  95   109    CONTINUE
  96   110 CONTINUE
  97   111 IF (MOD(IDO,2) .EQ. 1) RETURN
  98   105 DO 106 K=1,L1
  99          TI1 = CC(1,2,K)+CC(1,4,K)
 100          TI2 = CC(1,4,K)-CC(1,2,K)
 101          TR1 = CC(IDO,1,K)-CC(IDO,3,K)
 102          TR2 = CC(IDO,1,K)+CC(IDO,3,K)
 103          CH(IDO,K,1) = TR2+TR2
 104          CH(IDO,K,2) = SQRT2*(TR1-TI1)
 105          CH(IDO,K,3) = TI2+TI2
 106          CH(IDO,K,4) = -SQRT2*(TR1+TI1)
 107   106 CONTINUE
 108   107 RETURN
 109       END