SUBROUTINE BUNCHCROSS
	common /zquad/totcir,tloc(300),circ(300)
	common /crospnt/d(1000),ncross,ntrains,nbunches,nspace,angle
     &	  ,ncb(100,300),istart,l3,ncb1b2(100,100),last,nfind(1000)
	dimension e(1000),mcb1b2(100,100),mfind(1000),mcb(100,300)
	real*8 amat,xpel,ypel,expel,eldat,tleng,aleng,acleng
	include 'elements.inc'
c  d(i) is distance from IP to i crossing point
c  ncross is the number of parasitic crossing points
c  ntrains is the number of bunch trains
c  nspace=the bunch separation in units of 7 RF wavelengths
c  ncb(i,j) is true if bunch i has a close encounter at the j crossing point
	data lcd/7/   !lcd=least common denominator of RF wavelengths
	data mcb/30000*0/
	if(totcir.eq.0.)totcir=tleng/2
	ntotcir=183 !number of lcds in circumference
	wavelength=2*totcir/(ntotcir*lcd) !totcir=1/2 total circumference
	d(1)=0.
	n=1
	do 20 nt1=1,ntrains
	  ntrain1=INT(183*(nt1-1)/ntrains)
	  do 20 nb1=1,nbunches
	   nzb1=ntrain1+nspace*(nb1-1)
	      do 20 nt2=1,ntrains
	        ntrain2=INT(183*(nt2-1)/ntrains)
	          do 20 nb2=1,nbunches
		    nzb2=ntrain2+nspace*(nb2-1)
	            marg1=ntotcir+nzb1-nzb2
	            s=0.5*MOD(marg1,ntotcir)*lcd*wavelength
c  eliminate duplicates
	            do j=1,n   !see if s is the same as any previous s
	              if(s.eq.0.)s=totcir
	              if(s.eq.0.)goto 20
	              index=(nt1-1)*nbunches+nb1
	              if(s.eq.d(j))then
	                mcb(index,j)=1
	                n1=(nt1-1)*nbunches+nb1
	                n2=(nt2-1)*nbunches+nb2
	                mcb1b2(n1,n2)=j
	                goto 20
	                endif
	              end do
	            d(n)=s
	            n1=(nt1-1)*nbunches+nb1
	            n2=(nt2-1)*nbunches+nb2
	            mcb1b2(n1,n2)=n
	            mcb(index,n)=1
	    n=n+1
  20	  continue
	ncross=n-1
c  sort the list of crossing points
	do j=1,ncross
	  e(j)=d(j)
	  mfind(j)=j
	end do
	do jj=1,ncross
	  do kk=jj+1,ncross
	    j=mfind(jj)
	    k=mfind(kk)
	    if(e(k).lt.e(j))then
	      mfind(jj)=k
	      mfind(kk)=j
	      endif
	  end do
	end do
c
	do j=1,ncross
	  d(j)=e(mfind(j))
	  nfind(mfind(j))=j
	  end do
c
	nbuntot=ntrains*nbunches
c
	do j=1,ncross
	  do n1=1,nbuntot
	  ncb(n1,j)=0
	  end do
	end do
c
	do n1=1,nbuntot
	  do n2=1,nbuntot
	    n=mcb1b2(n1,n2)
	    ncb1b2(n1,n2)=nfind(n)
            if(mcb(n1,n).eq.1)ncb(n1,nfind(n))=1
	  end do
	end do
c
	return
	end