upinit.f

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C*********************************************************************
 
C...UPINIT
C...Dummy routine, to be replaced by a user implementing external
C...processes. Is supposed to fill the HEPRUP commonblock with info
C...on incoming beams and allowed processes.

C...New example: handles a standard Les Houches Events File.

      SUBROUTINE upinit
 
C...Double precision and integer declarations.
      IMPLICIT DOUBLE PRECISION(a-h, o-z)
      IMPLICIT INTEGER(i-n)
 
C...PYTHIA commonblock: only used to provide read unit MSTP(161).
      common/pypars/mstp(200),parp(200),msti(200),pari(200)
      SAVE /pypars/
 
C...User process initialization commonblock.
      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)
      SAVE /heprup/

C...Lines to read in assumed never longer than 200 characters. 
      parameter(maxlen=200)
      CHARACTER*(MAXLEN) string

C...Format for reading lines.
      CHARACTER*6 strfmt
      strfmt='(A000)'
      WRITE(strfmt(3:5),'(I3)') maxlen

C...Loop until finds line beginning with "<init>" or "<init ". 
  100 READ(mstp(161),strfmt,end=130,err=130) string
      ibeg=0
  110 ibeg=ibeg+1
C...Allow indentation.
      IF(string(ibeg:ibeg).EQ.' '.AND.ibeg.LT.maxlen-5) goto 110 
      IF(string(ibeg:ibeg+5).NE.'<init>'.AND.
     &string(ibeg:ibeg+5).NE.'<init ') goto 100

C...Read first line of initialization info.
      READ(mstp(161),*,end=130,err=130) idbmup(1),idbmup(2),ebmup(1),
     &ebmup(2),pdfgup(1),pdfgup(2),pdfsup(1),pdfsup(2),idwtup,nprup

C...Read NPRUP subsequent lines with information on each process.
      DO 120 ipr=1,nprup
        READ(mstp(161),*,end=130,err=130) xsecup(ipr),xerrup(ipr),
     &  xmaxup(ipr),lprup(ipr)
  120 CONTINUE
      RETURN

C...Error exit: give up if initalization does not work.
  130 WRITE(*,*) ' Failed to read LHEF initialization information.'
      WRITE(*,*) ' Event generation will be stopped.'
      CALL pystop(12)
 
      RETURN
      END