program ringtopo
  	 include 'mpif.h'

	   integer numtasks, rank, next, prev, buf(2), tag1, tag2, ierr
	   integer stats(MPI_STATUS_SIZE,2), reqs(2),reqs1(2)

	integer,parameter::buf_size=130
	real CRXi(10000),CP_sendx(buf_size)
	real CP_S6(6,buf_size),CP_R6(6,buf_size),xi(100000)
	real yi(100000),zi(100000),ui(100000),vi(100000),wi(100000)
	real CP_sendy(buf_size),CP_sendz(buf_size),CP_sendu(buf_size)
	real CP_sendv(buf_size),CP_sendw(buf_size)
	real CRYi(10000), CRZi(10000), CRUi(10000), CRVi(10000)
	real CRwi(10000)
	integer CP_send,CP_recv,ionsR,Max_p,n_p,LABEL_p,ions,loop
	
 	  tag1 = 1
 	  tag2 = 2
	do loop=1,2
	ions=5000
	do i=1,10000
	  CRxi(i)=i*1.0
	  CRyi(i)=i*2.0
	  CRzi(i)=i*3.0
	  CRui(i)=i*4.0
	  CRvi(i)=i*5.0
	  CRwi(i)=i*6.0
	end do
 	  call MPI_INIT(ierr)
 	  call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)
 	  call MPI_COMM_SIZE(MPI_COMM_WORLD, numtasks, ierr)

	   prev = rank - 1
	   next = rank + 1
 	  if (rank .eq. 0) then
 	     prev = numtasks - 1
 	  endif
 	  if (rank .eq. numtasks - 1) then
 	     next = 0
 	  endif

	ionsR=1120

C        do some work
	Max_p=ionsR/buf_size+1 
	LABEL_p=0
	CP_recv=20
	print*,CP_recv,Max_p,35335
	do 200 n_p=1,Max_p
	CP_send=0
	do i=1,buf_size
	n=LABEL_p+i
C	CP_S6(1,i)=CRXi(n)
	CP_sendx(i)=CRXi(n)
	CP_sendy(i)=CRyi(n)
	CP_sendz(i)=CRzi(n)

	CP_sendu(i)=CRui(n)
	CP_sendv(i)=CRvi(n)
	CP_sendw(i)=CRwi(n)
	end do
	CP_send=buf_size
	if(n.gt.ionsR)then
	CP_send=ionsR - LABEL_p
	if (CP_send.lt.0) CP_send=-CP_send
	end if
	LABEL_p=n

	do i=1,buf_size
	CP_S6(1,i)=CP_sendx(i)
	CP_S6(2,i)=CP_sendy(i)
	CP_S6(3,i)=CP_sendz(i)

	CP_S6(4,i)=CP_sendu(i)
	CP_S6(5,i)=CP_sendv(i)
	CP_S6(6,i)=CP_sendw(i)
	end do






C	print*,mreal,mint,lgrp,CP_send,reqs,1111114
C	print*,rank,MPI_INTEGER,CP_recv,CP_send,11111113
C	print*,rank,MPI_INTEGER,CP_R6(6,10),CP_s6(6,10),11111113
	print*,loop

 	  call MPI_IRECV(CP_recv, 1, MPI_INTEGER, prev, tag1, 
     &      MPI_COMM_WORLD, reqs(1), ierr)
 	  call MPI_ISEND(CP_send, 1, MPI_INTEGER, next, tag1,
     &     MPI_COMM_WORLD, reqs(2), ierr)

 	 call MPI_WAITALL(2, reqs, stats, ierr);  

  	 call MPI_IRECV(CP_R6, 6*CP_recv, MPI_REAL, prev, tag2, 
     &      MPI_COMM_WORLD, reqs1(1), ierr)
 	  call MPI_ISEND(CP_S6, 6*CP_send, MPI_REAL, next, tag2,
     &     MPI_COMM_WORLD, reqs1(2), ierr)

C	  call MPI_WAITALL(2, reqs1, stats, ierr);

	print*,rank,LABEL_p,CP_R6(6,10),CP_s6(6,10),11111114

	if (CP_recv.gt.0) then
	do n=1,CP_recv
	ions=ions+1
	xi(ions)=CP_R6(1,n)
	yi(ions)=CP_R6(2,n)
	zi(ions)=CP_R6(3,n)

	ui(ions)=CP_R6(4,n)
	vi(ions)=CP_R6(5,n)
	wi(ions)=CP_R6(6,n)	

	end do

	else
	print*,n_p,777777771,888888881
	End if

C110 	continue
C.......................

200	continue

	end do

	 call MPI_FINALIZE(ierr)

 	  end