#include <mpi.h>

#include <stdio.h>
#include <math.h>
#include <stdlib.h>

double myRand()
{
  return rand()/double(RAND_MAX);
}

int mpiError_=0;

int parallelStart(int& isPara,int& iProc,int& nProc,int argc,char* argv[])
{
  /*--Initialise MPI--------------------------------------------------------------------------------------------------------*/
  mpiError_=MPI_Init(&argc,&argv);

  /*--Find number of processes----------------------------------------------------------------------------------------------*/
  mpiError_=MPI_Comm_size(MPI_COMM_WORLD,&nProc);

  /*--Find rank------------------------------------------*/
  mpiError_=MPI_Comm_rank(MPI_COMM_WORLD,&iProc);

  if (nProc>1)
    isPara=1;

  return mpiError_;
}

int parallelStop()
{
  mpiError_=MPI_Finalize();
  return mpiError_;
}

int
main(int argc, char *argv[])
{
  int iError;
  int isPara,iProc,nProc,i,count;
  double *trans;
  double *local;
  double *global;
 
  /*--parallelStart starts MPI and returns the process index & number-------------------------------------------------------*/
  iError=parallelStart(isPara,iProc,nProc,argc,argv);

  printf("I am process %d out of %d, isPara=%d\n",iProc,nProc,isPara);fflush(stdout);

  trans = new double[nProc];
  local = new double[nProc];
  global= new double[nProc];

  srand(1234);

  for(count=0;count!=1;++count)
  {
    for(i=0;i!=nProc;i++)
      local[i]=myRand();

    for(i=0;i!=nProc;i++)
      trans[i]=local[iProc];

    MPI_Alltoall(trans,1,MPI_DOUBLE,global,1,MPI_DOUBLE,MPI_COMM_WORLD);

    /*--Validate everything-------------------------------------------------------------------------------*/
    for(i=0;i!=nProc;i++)
    {
      if (local[i]!=global[i])
        printf("%d Mismatch\n",iProc);fflush(stdout);
    }
  }

  delete [] trans;
  delete [] local;
  delete [] global;

  /*--Finalise MPI---------------------------------------------------------------------------------*/

  iError=parallelStop();

  return iError;
}