/********************************************************
% 
% Written by:
% -- 
% John L. Weatherwax                2006-05-29
% 
% email: wax@alum.mit.edu
% 
% Please send comments and especially bug reports to the
% above email address.
% 
%-----

*/

#include <math.h>
#include <stdio.h>
#include "mpi.h"
#include "global_grid.h"
#include "sim_consts.h"
#include "exhangeNumberOfParticlesToSend.h"

/* pass the number of particles each processor will obtain in various 
   MPI_Send sweeps ... this is required so that each processor can 
   create the space for all the particles that it will be receiving
*/ 
void exhangeNumberOfParticlesToSend(void){

  const int TAG_OFFSET=0; 
  MPI_Status status; 

  /* 
     Send NW <-> Receive SE 
  */ 
  /*printf("Send NW <-> Receive SE\n");*/
  if( procInfo.my_row % 2 == 0 ){   /* these processors will SEND    and then RECEIVE */ 
    MPI_Send(&procInfo.numToExport[NW],1,MPI_INT,procInfo.neighbor[NW],TAG_OFFSET+0,MPI_COMM_WORLD); 
    MPI_Recv(&procInfo.numToReceive[SE],1,MPI_INT,procInfo.neighbor[SE],TAG_OFFSET+0,MPI_COMM_WORLD,&status);
  }else{                            /* these processors will RECEIVE and then SEND */ 
    MPI_Recv(&procInfo.numToReceive[SE],1,MPI_INT,procInfo.neighbor[SE],TAG_OFFSET+0,MPI_COMM_WORLD,&status); 
    MPI_Send(&procInfo.numToExport[NW],1,MPI_INT,procInfo.neighbor[NW],TAG_OFFSET+0,MPI_COMM_WORLD); 
  }

  /* 
     Send N <-> Receive S 
  */ 
  if( procInfo.my_row % 2 == 0 ){   /* these processors will SEND    and then RECEIVE */ 
    MPI_Send(&procInfo.numToExport[N],1,MPI_INT,procInfo.neighbor[N],TAG_OFFSET+1,MPI_COMM_WORLD); 
    MPI_Recv(&procInfo.numToReceive[S],1,MPI_INT,procInfo.neighbor[S],TAG_OFFSET+1,MPI_COMM_WORLD,&status);
  }else{                            /* these processors will RECEIVE and then SEND */ 
    MPI_Recv(&procInfo.numToReceive[S],1,MPI_INT,procInfo.neighbor[S],TAG_OFFSET+1,MPI_COMM_WORLD,&status); 
    MPI_Send(&procInfo.numToExport[N],1,MPI_INT,procInfo.neighbor[N],TAG_OFFSET+1,MPI_COMM_WORLD); 
  }

  /* 
     Send NE <-> Receive SW 
  */ 
  /*printf("Send NE <-> Receive SW\n");*/
  if( procInfo.my_row % 2 == 0 ){   /* these processors will SEND    and then RECEIVE */ 
    MPI_Send(&procInfo.numToExport[NE],1,MPI_INT,procInfo.neighbor[NE],TAG_OFFSET+2,MPI_COMM_WORLD); 
    MPI_Recv(&procInfo.numToReceive[SW],1,MPI_INT,procInfo.neighbor[SW],TAG_OFFSET+2,MPI_COMM_WORLD,&status);
  }else{                            /* these processors will RECEIVE and then SEND */ 
    MPI_Recv(&procInfo.numToReceive[SW],1,MPI_INT,procInfo.neighbor[SW],TAG_OFFSET+2,MPI_COMM_WORLD,&status); 
    MPI_Send(&procInfo.numToExport[NE],1,MPI_INT,procInfo.neighbor[NE],TAG_OFFSET+2,MPI_COMM_WORLD);     
  }

  /* 
     Send W <-> Receive E 
  */ 
  if( procInfo.my_col % 2 == 0 ){    /* these processors will SEND    and then RECEIVE */ 
    MPI_Send(&procInfo.numToExport[W],1,MPI_INT,procInfo.neighbor[W],TAG_OFFSET+3,MPI_COMM_WORLD); 
    MPI_Recv(&procInfo.numToReceive[E],1,MPI_INT,procInfo.neighbor[E],TAG_OFFSET+3,MPI_COMM_WORLD,&status);
  }else{                             /* these processors will RECEIVE and then SEND */ 
    MPI_Recv(&procInfo.numToReceive[E],1,MPI_INT,procInfo.neighbor[E],TAG_OFFSET+3,MPI_COMM_WORLD,&status); 
    MPI_Send(&procInfo.numToExport[W],1,MPI_INT,procInfo.neighbor[W],TAG_OFFSET+3,MPI_COMM_WORLD); 
  }

  /* No sending to the IDENTITY */ 

  /* 
     Send E <-> Receive W 
  */ 
  if( procInfo.my_col % 2 == 0 ){    /* these processors will SEND    and then RECEIVE */ 
    MPI_Send(&procInfo.numToExport[E],1,MPI_INT,procInfo.neighbor[E],TAG_OFFSET+5,MPI_COMM_WORLD); 
    MPI_Recv(&procInfo.numToReceive[W],1,MPI_INT,procInfo.neighbor[W],TAG_OFFSET+5,MPI_COMM_WORLD,&status);
  }else{                             /* these processors will RECEIVE and then SEND */ 
    MPI_Recv(&procInfo.numToReceive[W],1,MPI_INT,procInfo.neighbor[W],TAG_OFFSET+5,MPI_COMM_WORLD,&status); 
    MPI_Send(&procInfo.numToExport[E],1,MPI_INT,procInfo.neighbor[E],TAG_OFFSET+5,MPI_COMM_WORLD); 
  }

  /* 
     Send SW <-> Receive NE 
  */ 
  /*printf("Send SW <-> Receive NE\n");*/
  if( procInfo.my_row % 2 == 0 ){   /* these processors will SEND    and then RECEIVE */ 
    MPI_Send(&procInfo.numToExport[SW],1,MPI_INT,procInfo.neighbor[SW],TAG_OFFSET+6,MPI_COMM_WORLD); 
    MPI_Recv(&procInfo.numToReceive[NE],1,MPI_INT,procInfo.neighbor[NE],TAG_OFFSET+6,MPI_COMM_WORLD,&status);
  }else{                            /* these processors will RECEIVE and then SEND */ 
    MPI_Recv(&procInfo.numToReceive[NE],1,MPI_INT,procInfo.neighbor[NE],TAG_OFFSET+6,MPI_COMM_WORLD,&status); 
    MPI_Send(&procInfo.numToExport[SW],1,MPI_INT,procInfo.neighbor[SW],TAG_OFFSET+6,MPI_COMM_WORLD);     
  }

  /* 
     Send S <-> Receive N 
  */ 
  if( procInfo.my_row % 2 == 0 ){    /* these processors will SEND    and then RECEIVE */ 
    MPI_Send(&procInfo.numToExport[S],1,MPI_INT,procInfo.neighbor[S],TAG_OFFSET+7,MPI_COMM_WORLD); 
    MPI_Recv(&procInfo.numToReceive[N],1,MPI_INT,procInfo.neighbor[N],TAG_OFFSET+7,MPI_COMM_WORLD,&status);
  }else{                             /* these processors will RECEIVE and then SEND */ 
    MPI_Recv(&procInfo.numToReceive[N],1,MPI_INT,procInfo.neighbor[N],TAG_OFFSET+7,MPI_COMM_WORLD,&status); 
    MPI_Send(&procInfo.numToExport[S],1,MPI_INT,procInfo.neighbor[S],TAG_OFFSET+7,MPI_COMM_WORLD); 
  }

  /* 
     Send SE <-> Receive NW 
  */ 
  /*printf("Send SE <-> Receive NW\n");*/
  if( procInfo.my_row % 2 == 0 ){   /* these processors will SEND    and then RECEIVE */ 
    MPI_Send(&procInfo.numToExport[SE],1,MPI_INT,procInfo.neighbor[SE],TAG_OFFSET+8,MPI_COMM_WORLD); 
    MPI_Recv(&procInfo.numToReceive[NW],1,MPI_INT,procInfo.neighbor[NW],TAG_OFFSET+8,MPI_COMM_WORLD,&status);
  }else{                            /* these processors will RECEIVE and then SEND */ 
    MPI_Recv(&procInfo.numToReceive[NW],1,MPI_INT,procInfo.neighbor[NW],TAG_OFFSET+8,MPI_COMM_WORLD,&status); 
    MPI_Send(&procInfo.numToExport[SE],1,MPI_INT,procInfo.neighbor[SE],TAG_OFFSET+8,MPI_COMM_WORLD);     
  }

}