*DECK EZFFT1 SUBROUTINE EZFFT1 (N, WA, IFAC) C***BEGIN PROLOGUE EZFFT1 C***SUBSIDIARY C***PURPOSE EZFFTI calls EZFFT1 with appropriate work array C partitioning. C***LIBRARY SLATEC (FFTPACK) C***TYPE SINGLE PRECISION (EZFFT1-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 references to intrinsic function FLOAT C to REAL, and C (c) changing definition of variable TPI by using C FORTRAN intrinsic function ATAN instead of a DATA C statement. C 881128 Modified by Dick Valent to meet prologue standards. C 890531 Changed all specific intrinsics to generic. (WRB) C 890531 REVISION DATE from Version 3.2 C 891214 Prologue converted to Version 4.0 format. (BAB) C 900402 Added TYPE section. (WRB) C***END PROLOGUE EZFFT1 DIMENSION WA(*), IFAC(*), NTRYH(4) SAVE NTRYH DATA NTRYH(1),NTRYH(2),NTRYH(3),NTRYH(4)/4,2,3,5/ C***FIRST EXECUTABLE STATEMENT EZFFT1 TPI = 8.*ATAN(1.) 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 ARGH = TPI/N IS = 0 NFM1 = NF-1 L1 = 1 IF (NFM1 .EQ. 0) RETURN DO 111 K1=1,NFM1 IP = IFAC(K1+2) L2 = L1*IP IDO = N/L2 IPM = IP-1 ARG1 = L1*ARGH CH1 = 1. SH1 = 0. DCH1 = COS(ARG1) DSH1 = SIN(ARG1) DO 110 J=1,IPM CH1H = DCH1*CH1-DSH1*SH1 SH1 = DCH1*SH1+DSH1*CH1 CH1 = CH1H I = IS+2 WA(I-1) = CH1 WA(I) = SH1 IF (IDO .LT. 5) GO TO 109 DO 108 II=5,IDO,2 I = I+2 WA(I-1) = CH1*WA(I-3)-SH1*WA(I-2) WA(I) = CH1*WA(I-2)+SH1*WA(I-3) 108 CONTINUE 109 IS = IS+IDO 110 CONTINUE L1 = L2 111 CONTINUE RETURN END