#include <stdlib.h>
#include <pnetcdf.h>
#include <stdio.h>
#include <mpi.h>

static void err(int status, int lineno)
{
    fprintf(stderr, "Error at line %d: %s\n", lineno, ncmpi_strerror(status));
    MPI_Abort(MPI_COMM_WORLD, 1);
}

int main(int argc, char **argv) {
  int ret, ncid=0, nprocs, rank, dimid1, dimid2, varid1=0, varid2=0, ndims=2;
  char buf[30] = "Collective read example\n";
  int dims[2];
  MPI_Offset sd[2];

  MPI_Init(&argc, &argv);

  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  MPI_Comm_size(MPI_COMM_WORLD, &nprocs);

  if (argc != 2) {
      if (rank == 0) printf("Usage: %s filename\n", argv[0]);
      MPI_Finalize();
      exit(-1);
  }

  // open the file  (is in define mode by default)
  ret = ncmpi_open(MPI_COMM_WORLD, argv[1], NC_NOWRITE, MPI_INFO_NULL, &ncid); 
  if (ret != NC_NOERR) err(ret, __LINE__);

  // query and check is the variable "v" is present
  ret = ncmpi_inq_varid(ncid, "v", &varid1);
  if (ret != NC_NOERR) err(ret, __LINE__);

  // query for the length of dimensions of the variable "v"
  ret = ncmpi_inq_dimlen(ncid, 0, &sd[0]);
  if (ret != NC_NOERR) err(ret, __LINE__);

  ret = ncmpi_inq_dimlen(ncid, 1, &sd[1]);
  if (ret != NC_NOERR) err(ret, __LINE__);

  printf("Dimensions: (%d, %d)\n", sd[0], sd[1]);

  MPI_Offset start[2], count[2];

  int  *data = (int*)malloc(sizeof(int)*sd[0]*sd[1]/nprocs);
  int i;
   
  start[0] = (sd[0]/nprocs)  * rank;
  start[1] =  0;
          
  count[0] = sd[0]/nprocs;
  count[1] = sd[1];

  // read variable using a collective (default)
  ret = ncmpi_get_vara_int_all(ncid, varid1, start, count, data);
  if (ret != NC_NOERR) err(ret, __LINE__);
  
  // close the file 
  ncmpi_close(ncid);

  printf("rank: %d, data[0]: %d\n", rank, data[0]);
  free(data);

  MPI_Finalize();
  return 0;
}