C-----------------------------------------------------------------------
      PROGRAM ZGEN
C-----------------------------------------------------------------------
C     Example main program
C-----------------------------------------------------------------------
      IMPLICIT NONE
C--Les Houches run common block
      INTEGER MAXPUP
      PARAMETER(MAXPUP=100)
      INTEGER IDBMUP,PDFGUP,PDFSUP,IDWTUP,NPRUP,LPRUP
      DOUBLE PRECISION EBMUP,XSECUP,XERRUP,XMAXUP
      COMMON /HEPRUP/ IDBMUP(2),EBMUP(2),PDFGUP(2),PDFSUP(2),
     &                IDWTUP,NPRUP,XSECUP(MAXPUP),XERRUP(MAXPUP),
     &                XMAXUP(MAXPUP),LPRUP(MAXPUP)
C--common block to pass the parameters
      DOUBLE PRECISION SMIN,SMAX
      INTEGER IPR
      COMMON /LPARAM/SMIN,SMAX,IPR
C--local variables
      DOUBLE PRECISION WGT
C--beam particles and energies (only proton=2212 and antiproton=-2212)
      IDBMUP(1) = 2212
      IDBMUP(2) = 2212
      EBMUP(1)  = 7000.0D0
      EBMUP(2)  = 7000.0D0
C--pdf's for the beams (use CTEQ5L)
C--MUST BE THE SAME FOR BOTH BEAMS
      PDFGUP(1) = 4
      PDFGUP(2) = 4
      PDFSUP(1) = 46
      PDFSUP(2) = 46
C--integration parameters
      SMIN = 10.0D0**2
      SMAX = (EBMUP(1)+EBMUP(2))**2
      print *,'limits on sqrt(sh)',sqrt(smin),sqrt(smax)
C--which process the following are supported
C      100 all fermion-antifermion production
C      110 all lepton production
C      120 all quark production
C      130+I production of the fermion i=(1,6 =e,ve,mu,vmu,tau,vtau)
C                                        (7,12-d,u,s,c,b,t)
      IPR = 110
C--test call to the weight generation routine
      CALL ZWGHT(WGT)
      END
C-----------------------------------------------------------------------
      SUBROUTINE ZWGHT(WGT)
C-----------------------------------------------------------------------
C     Subroutine to return the weight for a given phase space point
C-----------------------------------------------------------------------
      IMPLICIT NONE
C--Les Houches run common block
      INTEGER MAXPUP
      PARAMETER(MAXPUP=100)
      INTEGER IDBMUP,PDFGUP,PDFSUP,IDWTUP,NPRUP,LPRUP
      DOUBLE PRECISION EBMUP,XSECUP,XERRUP,XMAXUP
      COMMON /HEPRUP/ IDBMUP(2),EBMUP(2),PDFGUP(2),PDFSUP(2),
     &                IDWTUP,NPRUP,XSECUP(MAXPUP),XERRUP(MAXPUP),
     &                XMAXUP(MAXPUP),LPRUP(MAXPUP)
C--common block to pass the parameters
      DOUBLE PRECISION SMIN,SMAX
      INTEGER IPR
      COMMON /LPARAM/SMIN,SMAX,IPR
C--local variables
      DOUBLE PRECISION WGT,PIFAC,GEV2PB
      INTEGER IFERM(2)
      LOGICAL FIRST
      DATA FIRST/.TRUE./
      SAVE IFERM,FIRST,GEV2PB,PIFAC
C--useful parameters and initilisation
      IF(FIRST) THEN
C--constants
         PIFAC = ACOS(-1.0D0)
         FIRST = .FALSE.
C--conversion to picobarn from GeV
         GEV2PB=389379.D3
C--which processes to generate (IFERM controls the loop over final state fermions)
C--(e,ve,mu,vmu,tau,nvtau,d,u,s,c,b,t)
         IF(IPR.EQ.100) THEN
            IFERM(1) = 1
            IFERM(2) = 12
         ELSEIF(IPR.EQ.110) THEN
            IFERM(1) = 1
            IFERM(2) = 6
         ELSEIF(IPR.EQ.120) THEN
            IFERM(1) = 7
            IFERM(2) = 12
         ELSEIF(IPR.GE.131.AND.IPR.LE.142) THEN
            IFERM(1) = IPR-130
            IFERM(2) = IPR-130
         ELSE
            print *,'unknown process stopping'
            STOP
         ENDIF
         print *,'selected process code =',ipr
         print *,'limits on fermion loop',iferm
      ENDIF
      END