[netcdfgroup] possible bug in 4.3.3.1 with unlimited dimensions in NetCDF-4 format?

• To: "netcdfgroup@xxxxxxxxxxxxxxxx" <netcdfgroup@xxxxxxxxxxxxxxxx>
• Subject: [netcdfgroup] possible bug in 4.3.3.1 with unlimited dimensions in NetCDF-4 format?
• From: Ellen Johnson <Ellen.Johnson@xxxxxxxxxxxxx>
• Date: Tue, 3 Mar 2015 18:56:21 +0000

Hello,

  I just upgraded from NetCDF 4.1.3 to NetCDF 4.3.3.1 and am seeing a problem 
in our regression test when writing unlimited dimensions to a NetCDF-4 format 
file.  Specifically, if the unlimited dimension is last instead of the first in 
the dimension list, or if I declare more than one unlimited dimension, the 
program errors with the NC_EEDGE error:

    Error: NetCDF: Start+count exceeds dimension bound

  This does not occur in our current NetCDF version 4.1.3.
  To isolate the issue, I built NetCDF 4.3.3.1 outside of our build 
infrastructure and wrote a standalone C program to write to a NetCDF-4 file - 
so I am bypassing MATLAB completely.

  Can you please help me determine if this is a bug in the NetCDF code, 
specifically in dvarput.c?

  Below is the standalone C program that will throw the error above when 
linking to NetCDF 4.3.3.1.  Note I built this with HDF5 1.8.12.

  Thank you!
     Ellen Johnson
     Software Engineer
     Image and Scientific File Formats
     MathWorks


#include <stdio.h>
#include <string.h>
#include <netcdf.h>

#define FILE_NAME "unlim.nc"

/* 3D matrix, 6 x 4 x 3 */

#define NDIMS 3
#define X_LEN 6
#define Y_LEN 4
#define Z_LEN 3

/* Handle errors by printing an error message */
#define ERR(e) {printf("Error: %s\n", nc_strerror(e)); return 2;}
int
main()
{
    size_t start[NDIMS] = {0, 0, 0};
    size_t count[NDIMS] = {X_LEN, Y_LEN, Z_LEN};
    ptrdiff_t stride[NDIMS] = {1, 1, 1};
    float mydata[X_LEN * Y_LEN * Z_LEN];
    int i;
    int retval;

    int ncid, varid;
    int dimids[NDIMS];

    for (i = 0; i < (X_LEN * Y_LEN * Z_LEN); i++)
        mydata[i] = i;

    /* create the file in NetCDF-4 format */
    if ((retval = nc_create(FILE_NAME, NC_NETCDF4, &ncid)))
        ERR(retval);

    /* define dimensions */
    if ((retval = nc_def_dim(ncid, "time", X_LEN, &dimids[0])))
        ERR(retval);
    if ((retval = nc_def_dim(ncid, "lat", Y_LEN, &dimids[1])))
        ERR(retval);
    if ((retval = nc_def_dim(ncid, "lon", NC_UNLIMITED, &dimids[2])))
        ERR(retval);

   /* define the variable */
    if ((retval = nc_def_var(ncid, "data", NC_FLOAT, NDIMS, dimids, &varid)))
        ERR(retval);

    /* end define mode */
    if ((retval = nc_enddef(ncid)))
        ERR(retval);

    /* write data */
    if ((retval = nc_put_vars_float(ncid, varid, start, count, stride, mydata)))
        ERR(retval);

    /* close the file */
    if ((retval = nc_close(ncid)))
        ERR(retval);

    printf("\n\n*** SUCCESS writing example file %s!\n", FILE_NAME);
    return 0;
}