*DECK PASSB2 SUBROUTINE PASSB2 (IDO, L1, CC, CH, WA1) C***BEGIN PROLOGUE PASSB2 C***SUBSIDIARY C***PURPOSE Calculate the fast Fourier transform of subvectors of C length two. C***LIBRARY SLATEC (FFTPACK) C***TYPE SINGLE PRECISION (PASSB2-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 PASSB2 DIMENSION CC(IDO,2,*), CH(IDO,L1,2), WA1(*) C***FIRST EXECUTABLE STATEMENT PASSB2 IF (IDO .GT. 2) GO TO 102 DO 101 K=1,L1 CH(1,K,1) = CC(1,1,K)+CC(1,2,K) CH(1,K,2) = CC(1,1,K)-CC(1,2,K) CH(2,K,1) = CC(2,1,K)+CC(2,2,K) CH(2,K,2) = CC(2,1,K)-CC(2,2,K) 101 CONTINUE RETURN 102 IF(IDO/2.LT.L1) GO TO 105 DO 104 K=1,L1 CDIR$ IVDEP DO 103 I=2,IDO,2 CH(I-1,K,1) = CC(I-1,1,K)+CC(I-1,2,K) TR2 = CC(I-1,1,K)-CC(I-1,2,K) CH(I,K,1) = CC(I,1,K)+CC(I,2,K) TI2 = CC(I,1,K)-CC(I,2,K) CH(I,K,2) = WA1(I-1)*TI2+WA1(I)*TR2 CH(I-1,K,2) = WA1(I-1)*TR2-WA1(I)*TI2 103 CONTINUE 104 CONTINUE RETURN 105 DO 107 I=2,IDO,2 CDIR$ IVDEP DO 106 K=1,L1 CH(I-1,K,1) = CC(I-1,1,K)+CC(I-1,2,K) TR2 = CC(I-1,1,K)-CC(I-1,2,K) CH(I,K,1) = CC(I,1,K)+CC(I,2,K) TI2 = CC(I,1,K)-CC(I,2,K) CH(I,K,2) = WA1(I-1)*TI2+WA1(I)*TR2 CH(I-1,K,2) = WA1(I-1)*TR2-WA1(I)*TI2 106 CONTINUE 107 CONTINUE RETURN END