SUBROUTINE RFFTI1 (N,WA,IFAC) DIMENSION WA(1) ,IFAC(1) ,NTRYH(4) DATA NTRYH(1),NTRYH(2),NTRYH(3),NTRYH(4)/4,2,3,5/ NL = N NF = 0 J = 0 101 J = J+1 IF (J-4) 102,102,103 102 NTRY = NTRYH(J) GO TO 104 103 NTRY = NTRY+2 104 NQ = NL/NTRY NR = NL-NTRY*NQ IF (NR) 101,105,101 105 NF = NF+1 IFAC(NF+2) = NTRY NL = NQ IF (NTRY .NE. 2) GO TO 107 IF (NF .EQ. 1) GO TO 107 DO 106 I=2,NF IB = NF-I+2 IFAC(IB+2) = IFAC(IB+1) 106 CONTINUE IFAC(3) = 2 107 IF (NL .NE. 1) GO TO 104 IFAC(1) = N IFAC(2) = NF TPI = 6.28318530717959 ARGH = TPI/FLOAT(N) IS = 0 NFM1 = NF-1 L1 = 1 IF (NFM1 .EQ. 0) RETURN DO 110 K1=1,NFM1 IP = IFAC(K1+2) LD = 0 L2 = L1*IP IDO = N/L2 IPM = IP-1 DO 109 J=1,IPM LD = LD+L1 I = IS ARGLD = FLOAT(LD)*ARGH FI = 0. DO 108 II=3,IDO,2 I = I+2 FI = FI+1. ARG = FI*ARGLD WA(I-1) = COS(ARG) WA(I) = SIN(ARG) 108 CONTINUE IS = IS+IDO 109 CONTINUE L1 = L2 110 CONTINUE RETURN END