SUBROUTINE MFFTIV(C,IVSX,IESX,NVX,NEX,TABLES,IERR)**   PURPOSE:*       THIS SUBROUTINE PERFORMS AN INVERSE FOURIER TRANSFORM ALONG*       ONE DIMENSION OF A 2-DIMENSIONAL MATRIX, USING THE*       COOLEY-TUKEY ALGORITHM.*       THE INPUT MATRIX IS ASSUMED TO HAVE BEEN SUBJECTED*        TO A "BIT-REVERSAL" REORDERING ( THROUGH MFFTOV OR*       BECAUSE IT IS THE OUTPUT OF MFFDV AND HAS NOT BEEN REORDERED)*       THE SEQUENCE TO BE TRANSFORMED IS C[IVSX,NVX], WHOSE COMPONENTS*       ARE THE VECTORS C(M)[IESX,NEX].*       SEE REF.[1] FOR NOTATIONS.*  EXAMPLE:*       LET C BE A 2-D MATRIX C(N1,N2) DECLARED VIA*                 DIMENSION C(ID,N2)*       WITH ID.GE.N1.*       THEN THE IDFT ALONG THE FIRST DIMENSION IS OBTAINED BY*                 CALL MFFTIV(C,1,ID,N1,N2,TABLES,IERR)*       THE IDFT ALONG THE SECOND DIMENSION IS OBTAINED BY*                 CALL MFFTIV(C,ID,1,N2,N1,TABLES,IERR)*  IMPLEMENTATION:*       THE TRANSFORMATION IS IMPLEMENTED THROUGH REPEATED CALLS TO THE*       "BUTTERFLY" TRANSFORMATION MFFT?5; PARAMETERS OF THE "BUTTERFLY"*       ARE COMMUNICATED THROUGH THE COMMON BLOCK MFFTPA.*  ARGUMENTS:*       C : ARRAY TO BE TRANSFORMED.*       IVSX,IESX,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*  LOADING THE COMMON BLOCK : CONSTANTS      IVS=IVSX      IES=IESX      NV=NVX      NE=NEX      ILIM=(NE-1)*IES      LSTEP=IVS*  LOADING THE COMMON BLOCK : ITERATION-DEPENDENT QUANTITIES: INITIALIZA      LX=1      MX=NV*  SELECT THE HIGHEST FACTOR OF NV      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        LLIM=NUSTEP-LSTEP        LD2LIM=NUSTEP/2-LSTEP        MSTEP=NUSTEP*2        MLIM=NV*LSTEP-MSTEP        CALL MFFTA5(C,TABLES(0))        LX=LX+LX210   CONTINUE      IF(IFAC.EQ.1)RETURN*..  RADIX 3 LOOP300   CONTINUE      DO 310 IM=1,TABLES(-13)        MX=MX/3        NUSTEP=LX*LSTEP        LLIM=NUSTEP-LSTEP        MSTEP=NUSTEP*3        MLIM=NV*LSTEP-MSTEP        CALL MFFTB5(C,TABLES(0))        LX=LX*3310   CONTINUE      IF(IFAC.EQ.2)RETURN*..   RADIX 5 LOOP500   CONTINUE      DO 510 IM=1,TABLES(-12)        MX=MX/5        NUSTEP=LX*LSTEP        LLIM=NUSTEP-LSTEP        MSTEP=NUSTEP*5        MLIM=NV*LSTEP-MSTEP        CALL MFFTC5(C,TABLES(0))        LX=LX*5510   CONTINUE      END