SUBROUTINE MFFTP(N,W,ID,IERR)**     THIS SUBROUTINE PREPARES TABLES FOR USE BY THE MFFT*     ROUTINES. THE PARAMETERS ARE**     N : IS THE ORDER OF THE TRANSFORM;**     W : ARRAY OF LENGTH AT LEAST 4*N+14  WORDS IF ID=0,*      AND 4*N*(ID+1)+14 IF ID > 0 ; THIS ARRAY IS FILLED*      BY THE PRESENT ROUTINE, AND SHOULD NOT BE MODIFIED BY THE*      USER; IT IS REQUIRED BY ALL THE OPERATING ROUTINES;*      THE ROUTINES MFFTIS AND MFFTDS*      REQUIRE THAT W HAS BEEN FILLED BY A CALL TO MFFTP WITH*      ID .GT. 0 ; ALL THE ROUTINES DO NOT MODIFY THE CONTENTS*      OF W ;*      WARNING: DIFFERENT PORTIONS OF W ARE HANDLED AS COMPLEX OR*               INTEGER VARIABLES BY DIFFERENT ROUTINES.**     ID : IF ID .EQ. 0 THE TABLES ARE SET FOR A NORMAL*      TRANSFORM; IF ID .GT. 0 THE TABLES ARE SET FOR BOTH*      A NORMAL AND A "SPECIAL" TRANSFORM (I.E. OPTIMIZED FOR SMALL*      FIRST DIMENSION DATA ARRAYS, SEE REF.[2]); IN THIS CASE IT*      SHOULD BE EQUAL TO THE FIRST DIMENSION OF THE ARRAY TO BE*      TRANSFORMED, AS DECLARED IN THE CALLING PROGRAM.**     IERR : ERROR CODE : =0 : SUCCESSFUL*                       : =2 : FACTORIZATION ERROR*****************************************************************      REFERENCE INFORMATION : LAYOUT OF W**  IN ALL CASES** WORD ADDRESS      TYPE    N. OF EL. WORD LENGTH   PURPOSE**  0                INTEGER      14      14     FACTORIZATION OF N**  14               COMPLEX     N       2*N     EXP(I*P/(2*N)*K),K=*                                               0,N-1*  3*N+14           INTEGER     N        N      PERMUTATION INDEX:KOFI*  2*N+14           INTEGER     N        N      PERMUTATION INDEX:IOFK**  ONLY IF ID .GT. 0**  4*N+14           COMPLEX    N*ID     2*N*ID  TABLES FOR MFFTDS*  4*N+2*N*ID+14    COMPLEX    N*ID     2*N*ID  TABLES FOR MFFTIS**********************************************************************      COMPLEX W(-7:*) *...  FACTORIZATION OF N IN W(-7)..W(-1)      CALL MFFTP1(W(-7),N,IERR)      IF(IERR.NE.0)RETURN**     PREPARATION OF PERMUTATION INDEXES IN W(N)..W(2*N-1)*     WARNING : W(0)..W(N-1) USED AS A WORK SPACE      CALL MFFTP2(W(N),W(0),W(-7),N)**     PREPARATION OF PHASE FACTOR TABLE IN W(0)..W(N-1)      W(0)=1.0      PI2DN=ATAN(1.)*8./N      DO 1  I=1,N-1        W(I)=CMPLX(COS(PI2DN*I),SIN(PI2DN*I))1     CONTINUE**     IF TABLES FOR SPECIAL TRANSFORM ARE REQUESTED      IF(ID.GT.0)THEN        CALL MFFTP4(W(0),W(2*N),W(-7),N,ID)      ENDIF*      END