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61 lines
2 KiB
Fortran
61 lines
2 KiB
Fortran
*DECK RADF2
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SUBROUTINE RADF2 (IDO, L1, CC, CH, WA1)
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C***BEGIN PROLOGUE RADF2
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C***SUBSIDIARY
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C***PURPOSE Calculate the fast Fourier transform of subvectors of
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C length two.
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C***LIBRARY SLATEC (FFTPACK)
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C***TYPE SINGLE PRECISION (RADF2-S)
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C***AUTHOR Swarztrauber, P. N., (NCAR)
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C***ROUTINES CALLED (NONE)
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C***REVISION HISTORY (YYMMDD)
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C 790601 DATE WRITTEN
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C 830401 Modified to use SLATEC library source file format.
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C 860115 Modified by Ron Boisvert to adhere to Fortran 77 by
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C changing dummy array size declarations (1) to (*).
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C 881128 Modified by Dick Valent to meet prologue standards.
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C 890831 Modified array declarations. (WRB)
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C 891214 Prologue converted to Version 4.0 format. (BAB)
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C 900402 Added TYPE section. (WRB)
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C***END PROLOGUE RADF2
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DIMENSION CH(IDO,2,*), CC(IDO,L1,2), WA1(*)
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C***FIRST EXECUTABLE STATEMENT RADF2
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DO 101 K=1,L1
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CH(1,1,K) = CC(1,K,1)+CC(1,K,2)
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CH(IDO,2,K) = CC(1,K,1)-CC(1,K,2)
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101 CONTINUE
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IF (IDO-2) 107,105,102
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102 IDP2 = IDO+2
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IF((IDO-1)/2.LT.L1) GO TO 108
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DO 104 K=1,L1
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CDIR$ IVDEP
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DO 103 I=3,IDO,2
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IC = IDP2-I
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TR2 = WA1(I-2)*CC(I-1,K,2)+WA1(I-1)*CC(I,K,2)
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TI2 = WA1(I-2)*CC(I,K,2)-WA1(I-1)*CC(I-1,K,2)
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CH(I,1,K) = CC(I,K,1)+TI2
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CH(IC,2,K) = TI2-CC(I,K,1)
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CH(I-1,1,K) = CC(I-1,K,1)+TR2
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CH(IC-1,2,K) = CC(I-1,K,1)-TR2
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103 CONTINUE
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104 CONTINUE
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GO TO 111
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108 DO 110 I=3,IDO,2
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IC = IDP2-I
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CDIR$ IVDEP
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DO 109 K=1,L1
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TR2 = WA1(I-2)*CC(I-1,K,2)+WA1(I-1)*CC(I,K,2)
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TI2 = WA1(I-2)*CC(I,K,2)-WA1(I-1)*CC(I-1,K,2)
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CH(I,1,K) = CC(I,K,1)+TI2
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CH(IC,2,K) = TI2-CC(I,K,1)
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CH(I-1,1,K) = CC(I-1,K,1)+TR2
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CH(IC-1,2,K) = CC(I-1,K,1)-TR2
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109 CONTINUE
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110 CONTINUE
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111 IF (MOD(IDO,2) .EQ. 1) RETURN
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105 DO 106 K=1,L1
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CH(1,2,K) = -CC(IDO,K,2)
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CH(IDO,1,K) = CC(IDO,K,1)
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106 CONTINUE
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107 RETURN
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END
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