SUBROUTINE MFFTIS(C,IMSX,IVSX,IESX,NMX,NVX,NEX,TABLES,IERR)*   PURPOSE:*       THE SAME AS MFFTIM.  IT IS A VARIANT OF MFFTIM, OPTIMIZED FOR*       MAXIMUM PERFORMANCE ON MATRICES WHOSE FIRST DIMENSION IS*       LESS THAN 64.*       IT REQUIRES THAT TABLES HAS BEEN PREPARED BY A CALL TO MFFTP*       WITH ID .NE. 0 .*  IMPLEMENTATION:*       THE TRANSFORMATION IS IMPLEMENTED THROUGH REPEATED CALLS TO THE*       "BUTTERFLY" TRANSFORMATION MFFT?9; PARAMETERS OF THE "BUTTERFLY"*       ARE COMMUNICATED THROUGH THE COMMON BLOCK MFFTPA.*  ARGUMENTS:*    INPUT:*       C : ARRAY TO BE TRANSFORMED.*       IMSX,IVSX,IESX,NMX,NVX,NEX: THESE ARGUMENTS DEFINE THE STRUCTURE*           OF C ACCORDING TO THE DEFINITIONS ABOVE. THEY ARE UNCHANGED*           ON OUTPUT*       TABLES : ARRAY PREPARED BY MFFTP. IT  IS NOT CHANGED ON OUTPUT.*                IT SHOULD BE DECLARED INTEGER TABLES(4*NM+14);*                IT MUST BE INITIALIZED BY MFFTP BEFORE USAGE.*    OUTPUT:*       C : TRANSFORM OF THE ORIGINAL ARRAY; "BIT REVERSED" ORDER*       IERR : ERROR CODE : =0 : SUCCESSFUL*                         : =3 :  'TABLES' NOT CORRECTLY INITIALIZED      COMPLEX C(*)      INTEGER TABLES(-14:*)      INTEGER IDERR,FACERR,TBERR      PARAMETER (IDERR=1,FACERR=2,TBERR=3)      COMMON /MFFTPA/  IMS,IVS,IES,NM,NV,NE,MX,LX,MLIM,MSTEP,LLIM,LSTEP,     $ NUSTEP,IVLIM,ILIM,MD2LIM,LD2LIM      SAVE IBASE*  LOADING THE COMMON BLOCK : CONSTANTS      IMS=IMSX      IVS=IVSX      IES=1      NM=NMX      NV=NVX      NE=NEX       IVLIM=(NV-1)*IVS      LSTEP=IMS*  LOADING THE COMMON BLOCK : ITERATION-DEPENDENT QUANTITIES: INITIALIZA      LX=1      MX=NM       IBASE=(2+IMS)*NM      IFAC=TABLES(-1)      IF(IFAC.GT.3)THEN        IERR=TBERR        RETURN      ENDIF*..   RADIX 2 LOOP200   CONTINUE      DO 210 IM=1,TABLES(-14)        MX=MX/2        NUSTEP=LX*LSTEP        ILIM=NUSTEP-1        MSTEP=NUSTEP*2        MLIM=NM*LSTEP-MSTEP        CALL MFFTA9(C,TABLES(2*IBASE))        LX=LX+LX        IBASE=IBASE+NUSTEP210   CONTINUE      IF(IFAC.EQ.1)RETURN*..   RADIX 3 LOOP300   CONTINUE      DO 310 IM=1,TABLES(-13)        MX=MX/3        NUSTEP=LX*LSTEP        ILIM=NUSTEP-1        MSTEP=NUSTEP*3        MLIM=NM*LSTEP-MSTEP        CALL MFFTB9(C,TABLES(2*IBASE))        LX=LX*3        IBASE=IBASE+NUSTEP*2310   CONTINUE      IF(IFAC.EQ.2)RETURN*..   RADIX 5 LOOP500   CONTINUE      DO 510 IM=1,TABLES(-12)        MX=MX/5        NUSTEP=LX*LSTEP        ILIM=NUSTEP-1        MSTEP=NUSTEP*5        MLIM=NM*LSTEP-MSTEP        CALL MFFTC9(C,TABLES(2*IBASE))        LX=LX*5        IBASE=IBASE+NUSTEP*4510   CONTINUE      END