upevnt.f

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C...Old example: handles a simple Pythia 6.4 initialization file.
 
c      SUBROUTINE UPINIT
 
C...Double precision and integer declarations.
c      IMPLICIT DOUBLE PRECISION(A-H, O-Z)
c      IMPLICIT INTEGER(I-N)
 
C...Commonblocks.
c      COMMON/PYDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
c      COMMON/PYPARS/MSTP(200),PARP(200),MSTI(200),PARI(200)
c      SAVE /PYDAT1/,/PYPARS/
 
C...User process initialization commonblock.
c      INTEGER MAXPUP
c      PARAMETER (MAXPUP=100)
c      INTEGER IDBMUP,PDFGUP,PDFSUP,IDWTUP,NPRUP,LPRUP
c      DOUBLE PRECISION EBMUP,XSECUP,XERRUP,XMAXUP
c      COMMON/HEPRUP/IDBMUP(2),EBMUP(2),PDFGUP(2),PDFSUP(2),
c     &IDWTUP,NPRUP,XSECUP(MAXPUP),XERRUP(MAXPUP),XMAXUP(MAXPUP),
c     &LPRUP(MAXPUP)
c      SAVE /HEPRUP/
 
C...Read info from file.
c      IF(MSTP(161).GT.0) THEN
c        READ(MSTP(161),*,END=110,ERR=110) IDBMUP(1),IDBMUP(2),EBMUP(1),
c     &  EBMUP(2),PDFGUP(1),PDFGUP(2),PDFSUP(1),PDFSUP(2),IDWTUP,NPRUP
c        DO 100 IPR=1,NPRUP
c          READ(MSTP(161),*,END=110,ERR=110) XSECUP(IPR),XERRUP(IPR),
c     &    XMAXUP(IPR),LPRUP(IPR)
c  100   CONTINUE
c        RETURN
C...Error or prematurely reached end of file.
c  110   WRITE(MSTU(11),5000)
c        STOP
 
C...Else not implemented.
c      ELSE
c        WRITE(MSTU(11),5100)
c        STOP
c      ENDIF
 
C...Format for error printout.
c 5000 FORMAT(1X,'Error: UPINIT routine failed to read information'/
c     &1X,'Execution stopped!')
c 5100 FORMAT(1X,'Error: You have not implemented UPINIT routine'/
c     &1X,'Dummy routine in PYTHIA file called instead.'/
c     &1X,'Execution stopped!')
 
c      RETURN
c      END
 
C*********************************************************************
 
C...UPEVNT
C...Dummy routine, to be replaced by a user implementing external
C...processes. Depending on cross section model chosen, it either has
C...to generate a process of the type IDPRUP requested, or pick a type
C...itself and generate this event. The event is to be stored in the
C...HEPEUP commonblock, including (often) an event weight.

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

      SUBROUTINE upevnt
 
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(162).
      common/pypars/mstp(200),parp(200),msti(200),pari(200)
      SAVE /pypars/
 
C...User process event common block.
      INTEGER maxnup
      parameter(maxnup=500)
      INTEGER nup,idprup,idup,istup,mothup,icolup
      DOUBLE PRECISION xwgtup,scalup,aqedup,aqcdup,pup,vtimup,spinup
      common/hepeup/nup,idprup,xwgtup,scalup,aqedup,aqcdup,idup(maxnup),
     &istup(maxnup),mothup(2,maxnup),icolup(2,maxnup),pup(5,maxnup),
     &vtimup(maxnup),spinup(maxnup)
      SAVE /hepeup/

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 "<event>" or "<event ". 
  100 READ(mstp(162),strfmt,end=130,err=130) string
      ibeg=0
  110 ibeg=ibeg+1
C...Allow indentation.
      IF(string(ibeg:ibeg).EQ.' '.AND.ibeg.LT.maxlen-6) goto 110 
      IF(string(ibeg:ibeg+6).NE.'<event>'.AND.
     &string(ibeg:ibeg+6).NE.'<event ') goto 100

C...Read first line of event info.
      READ(mstp(162),*,end=130,err=130) nup,idprup,xwgtup,scalup,
     &aqedup,aqcdup

C...Read NUP subsequent lines with information on each particle.
      DO 120 i=1,nup
        READ(mstp(162),*,end=130,err=130) idup(i),istup(i),
     &  mothup(1,i),mothup(2,i),icolup(1,i),icolup(2,i),
     &  (pup(j,i),j=1,5),vtimup(i),spinup(i)
  120 CONTINUE
      RETURN

C...Error exit, typically when no more events.
  130 WRITE(*,*) ' Failed to read LHEF event information.'
      WRITE(*,*) ' Will assume end of file has been reached.'
      nup=0
      msti(51)=1
 
      RETURN
      END