*DECK RADB3 SUBROUTINE RADB3 (IDO, L1, CC, CH, WA1, WA2) C***BEGIN PROLOGUE RADB3 C***SUBSIDIARY C***PURPOSE Calculate the fast Fourier transform of subvectors of C length three. C***LIBRARY SLATEC (FFTPACK) C***TYPE SINGLE PRECISION (RADB3-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 (a) changing dummy array size declarations (1) to (*), C (b) changing definition of variable TAUI by using C FORTRAN intrinsic function SQRT instead of a DATA C statement. 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 RADB3 DIMENSION CC(IDO,3,*), CH(IDO,L1,3), WA1(*), WA2(*) C***FIRST EXECUTABLE STATEMENT RADB3 TAUR = -.5 TAUI = .5*SQRT(3.) DO 101 K=1,L1 TR2 = CC(IDO,2,K)+CC(IDO,2,K) CR2 = CC(1,1,K)+TAUR*TR2 CH(1,K,1) = CC(1,1,K)+TR2 CI3 = TAUI*(CC(1,3,K)+CC(1,3,K)) CH(1,K,2) = CR2-CI3 CH(1,K,3) = CR2+CI3 101 CONTINUE IF (IDO .EQ. 1) RETURN IDP2 = IDO+2 IF((IDO-1)/2.LT.L1) GO TO 104 DO 103 K=1,L1 CDIR$ IVDEP DO 102 I=3,IDO,2 IC = IDP2-I TR2 = CC(I-1,3,K)+CC(IC-1,2,K) CR2 = CC(I-1,1,K)+TAUR*TR2 CH(I-1,K,1) = CC(I-1,1,K)+TR2 TI2 = CC(I,3,K)-CC(IC,2,K) CI2 = CC(I,1,K)+TAUR*TI2 CH(I,K,1) = CC(I,1,K)+TI2 CR3 = TAUI*(CC(I-1,3,K)-CC(IC-1,2,K)) CI3 = TAUI*(CC(I,3,K)+CC(IC,2,K)) DR2 = CR2-CI3 DR3 = CR2+CI3 DI2 = CI2+CR3 DI3 = CI2-CR3 CH(I-1,K,2) = WA1(I-2)*DR2-WA1(I-1)*DI2 CH(I,K,2) = WA1(I-2)*DI2+WA1(I-1)*DR2 CH(I-1,K,3) = WA2(I-2)*DR3-WA2(I-1)*DI3 CH(I,K,3) = WA2(I-2)*DI3+WA2(I-1)*DR3 102 CONTINUE 103 CONTINUE RETURN 104 DO 106 I=3,IDO,2 IC = IDP2-I CDIR$ IVDEP DO 105 K=1,L1 TR2 = CC(I-1,3,K)+CC(IC-1,2,K) CR2 = CC(I-1,1,K)+TAUR*TR2 CH(I-1,K,1) = CC(I-1,1,K)+TR2 TI2 = CC(I,3,K)-CC(IC,2,K) CI2 = CC(I,1,K)+TAUR*TI2 CH(I,K,1) = CC(I,1,K)+TI2 CR3 = TAUI*(CC(I-1,3,K)-CC(IC-1,2,K)) CI3 = TAUI*(CC(I,3,K)+CC(IC,2,K)) DR2 = CR2-CI3 DR3 = CR2+CI3 DI2 = CI2+CR3 DI3 = CI2-CR3 CH(I-1,K,2) = WA1(I-2)*DR2-WA1(I-1)*DI2 CH(I,K,2) = WA1(I-2)*DI2+WA1(I-1)*DR2 CH(I-1,K,3) = WA2(I-2)*DR3-WA2(I-1)*DI3 CH(I,K,3) = WA2(I-2)*DI3+WA2(I-1)*DR3 105 CONTINUE 106 CONTINUE RETURN END