SUBROUTINE MFFTRI(C,ISV,ISE,NV,NE,RW)**   PURPOSE:*       THIS ROUTINE PERFORMS THE PRE-PROCESSING PHASE FOR*       REAL 2-DIMENSIONAL INVERSE DFT'S (SEE FORMULA (2.7)*       IN REF.[1]).*       PRE-PROCESSING ACTS ON SEQUENTAL DATA BEFORE A CALL TO*       MFFTOV AN BEFORE COMPUTING THE IDFT (A CALL TO MFFTIV)*       AND EVENTUAL REORDERING (CALLS TO MFFTIV AND MFFTOV).*       IT APPLIES TO A VECTOR-OF-VECTORS-OF-COMPLEX*               C[IVS,NV [IES,NE]].*       SEE REF.[1] FOR NOTATIONS.**   ARGUMENTS:*      INPUT:*       C : DATA ARRAY, OUTPUT FROM MFFTDV, MFFTOV; TO BE DECLARED*                      REAL C(ISE*2,NE)*           IN THE CALLING PROGRAM.*     ISV : SEPARATION OF ELEMENTS IN A COLUMN OF C (USUALLY 1)*     ISE : SEPARATION OF ELEMENTS IN A ROW OF C, DIVIDED BY 2*      NV : NO. OF ELEMENTS TO BE PROCESSED IN A COLUMN OF C*      NE : NO. OF ELEMENTS IN A ROW OF C, DIVIDED BY 2.*      RW : COMPLEX ARRAY OF LENGHT AT LEAST NV; IT MUST*           BE INITIALIZED BY A CALL TO MFFTRP; IT REMAINS*           UNCHANGED IN OUTPUT.**  OUTPUT : POST-PROCESSED ARRAY C**      COMPLEX C(0:ISV-1,0:*),RW(0:*),T1,T2**      IF(NV.GT.1) THEN*      DO 200 IV=1,(NV-1)/2        DO 190 IE=0,(NE-1)*ISE,ISE        T1=C(IE,IV)        T2=C(IE,NV-IV)*        C(IE,IV)=(T1+CONJG(T2))+(CONJG(RW(IV))*(T1-CONJG(T2)))        C(IE,NV-IV)=CONJG(T1+CONJG(T2))-CONJG(CONJG(RW(IV))*(T1-     $              CONJG(T2)))   190    CONTINUE 200   CONTINUE**        IF(2*IV.EQ.NV) THEN*        DO 210 IE=0,(NE-1)*ISE,ISE        C(IE,IV)=2*CONJG(C(IE,IV)) 210   CONTINUE**      ENDIF*      ENDIF**      DO 220 IE=0,(NE-1)*ISE,ISE         RP=REAL(C(IE,0))+REAL(C(IE,NV))         RM=REAL(C(IE,0))-REAL(C(IE,NV))         C(IE,0)=CMPLX(RP,RM) 220  CONTINUE**      END