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- *DECK RADB2
- SUBROUTINE RADB2 (IDO, L1, CC, CH, WA1)
- C***BEGIN PROLOGUE RADB2
- C***SUBSIDIARY
- C***PURPOSE Calculate the fast Fourier transform of subvectors of
- C length two.
- C***LIBRARY SLATEC (FFTPACK)
- C***TYPE SINGLE PRECISION (RADB2-S)
- C***AUTHOR Swarztrauber, P. N., (NCAR)
- C***ROUTINES CALLED (NONE)
- C***REVISION HISTORY (YYMMDD)
- C 790601 DATE WRITTEN
- C 830401 Modified to use SLATEC library source file format.
- C 860115 Modified by Ron Boisvert to adhere to Fortran 77 by
- C changing dummy array size declarations (1) to (*).
- C 881128 Modified by Dick Valent to meet prologue standards.
- C 890831 Modified array declarations. (WRB)
- C 891214 Prologue converted to Version 4.0 format. (BAB)
- C 900402 Added TYPE section. (WRB)
- C***END PROLOGUE RADB2
- DIMENSION CC(IDO,2,*), CH(IDO,L1,2), WA1(*)
- C***FIRST EXECUTABLE STATEMENT RADB2
- DO 101 K=1,L1
- CH(1,K,1) = CC(1,1,K)+CC(IDO,2,K)
- CH(1,K,2) = CC(1,1,K)-CC(IDO,2,K)
- 101 CONTINUE
- IF (IDO-2) 107,105,102
- 102 IDP2 = IDO+2
- IF((IDO-1)/2.LT.L1) GO TO 108
- DO 104 K=1,L1
- CDIR$ IVDEP
- DO 103 I=3,IDO,2
- IC = IDP2-I
- CH(I-1,K,1) = CC(I-1,1,K)+CC(IC-1,2,K)
- TR2 = CC(I-1,1,K)-CC(IC-1,2,K)
- CH(I,K,1) = CC(I,1,K)-CC(IC,2,K)
- TI2 = CC(I,1,K)+CC(IC,2,K)
- CH(I-1,K,2) = WA1(I-2)*TR2-WA1(I-1)*TI2
- CH(I,K,2) = WA1(I-2)*TI2+WA1(I-1)*TR2
- 103 CONTINUE
- 104 CONTINUE
- GO TO 111
- 108 DO 110 I=3,IDO,2
- IC = IDP2-I
- CDIR$ IVDEP
- DO 109 K=1,L1
- CH(I-1,K,1) = CC(I-1,1,K)+CC(IC-1,2,K)
- TR2 = CC(I-1,1,K)-CC(IC-1,2,K)
- CH(I,K,1) = CC(I,1,K)-CC(IC,2,K)
- TI2 = CC(I,1,K)+CC(IC,2,K)
- CH(I-1,K,2) = WA1(I-2)*TR2-WA1(I-1)*TI2
- CH(I,K,2) = WA1(I-2)*TI2+WA1(I-1)*TR2
- 109 CONTINUE
- 110 CONTINUE
- 111 IF (MOD(IDO,2) .EQ. 1) RETURN
- 105 DO 106 K=1,L1
- CH(IDO,K,1) = CC(IDO,1,K)+CC(IDO,1,K)
- CH(IDO,K,2) = -(CC(1,2,K)+CC(1,2,K))
- 106 CONTINUE
- 107 RETURN
- END
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