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Hi Kari, > Actually, I have a workaround: I use unlimited for time dimension and I > have verified that the big cubes work. > > I was just testing this setup for reading speed. We now are serving > modis4 data directly out of 85 GB netcdf file at > http://128.252.202.19:8080/NASA > So the reading speed is quite important, and I found this bug while > benchmarking. We found the cause of the bug and a fix for it. The fix will be in the next snapshot release. This bug has been in the code since 2004, when the 64-bit offset format was first added to netCDF 3.6.0, so it's great that you discovered it and sent in a reproducible test case that demonstrated it. The bug occurs if all of the following conditions are true: - writing a variable of any type with more than 2**32 values - the variable must have 2 or more dimensions - the platform on which the file is written must be 32-bit - the file can be either classic format or 64-bit offset format - the values to be written must begin beyond the first 2**32 values In this case, a file offset is computed for writing using 32-bit arithmetic for a multiply, but it should be using 64-bit arithmetic. This results in an undetected integer overflow and can overwrite data earlier in the file, without an error or warning. The one-line fix is to change a statement in libsrc/putget.c from lcoord += *up * *ip; to lcoord += (off_t)(*up) * (off_t)(*ip); Thanks again for reporting this bug! --Russ > I'm already using HDF5 version 1.8.4-patch1 > > I compiled my library from > ftp://ftp.unidata.ucar.edu/pub/netcdf/netcdf.tar.gz for win32. > > Kari > > > Howdy Kari! > > > > Looks like you found a bug of some kind. I have reproduced your problem in > > the netCDF build with new test libsrc4/tst_large2.c. > > > > Now we will work on a fix. I will let you know when we have it. Meanwhile, > > as a workaround, I note that the NC_NETCDF4 format works fine for your test > > program. > > > > If you are going to use netCDF-4, make sure you get the HDF5-1.8.4-patch1 > > release, and the recent 4.1.1 release of netcdf. > > > > Thanks, > > > > Ed > > > > > > Ticket Details > > =================== > > Ticket ID: DFM-455316 > > Department: Support netCDF > > Priority: Normal > > Status: Open > > > > > > > > Russ Rew UCAR Unidata Program address@hidden http://www.unidata.ucar.edu Ticket Details =================== Ticket ID: DFM-455316 Department: Support netCDF Priority: Critical Status: Closed