The problem occurs in Cray (float2) mode when calling a netCDF put routine.
On the NEC SX, netCDF converts from Cray to IEEE floating point by calling the
NEC function fl2_ie3 from various places in src/libsrc/ncx.c. Underflow is
possible because the Cray format has more exponent bits. Each underflow
generates the (normally) desired value of 0, but does not increment the
function result, which is a count of correct conversions. E.g. 3 underflows
in a vector of 8 elements would give a result of 5. NetCDF detects the fact
that this result is less than expected & generates error -60. There appears
to be no way of modifying the behaviour of fl2_ie3 to count underflows as
normal conversions.
One solution would be to count the values small enough in magnitude to
underflow before calling fl2_ie3. However, I suspect this would be too costly
in time to be worthwhile. So (unless I am being too pessimistic here and
Glenn Davis implements some such solution in ncx.c) the user should anticipate
the possibility of error -60 occuring in put routines.
Harvey Davies, CSIRO Mathematical and Information Sciences,
Email: harvey.davies@xxxxxxxxxxxxx
Phone: +61 3 9669 8110 or +61 3 9239 4556
Fax: +61 3 9669 8112
>From owner-netcdfgroup@xxxxxxxxxxxxxxxx Mon 9 1998 Mar 15:15:31
Date: Mon, 9 Mar 1998 15:15:31 -0500
From: Fred Knight <knight@xxxxxxxxxx>
To: netcdfgroup@xxxxxxxxxxxxxxxx
Subject: request: plotting utility
Received: (from daemon@localhost)
by unidata.ucar.edu (8.8.8/8.8.8) id NAA19504
for netcdfgroup-out; Mon, 9 Mar 1998 13:16:30 -0700 (MST)
Keywords: 199803092016.NAA19500
Message-Id: <9803091515.AA18386@xxxxxxxxxx>
Organization: Lincoln Laboratory
X-Mailer: Mozilla 3.04Gold (X11; I; SunOS 5.4 sun4c)
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: owner-netcdfgroup@xxxxxxxxxxxxxxxx
Precedence: bulk
Reply-To: Fred Knight <knight@xxxxxxxxxx>
I want to browse a netCDF file and be able to make plots.
I have a utility written by a summer student at NCAR. It runs under
IDL, is called ncbrowse, works fairly well, and is an aid to seeing what
is in a netCDF file. It also requires IDL and doesn't plot one vector
wrt another vector.
So I'm looking for a Unix utility with X interface to browse a netCDF
file and plot variables, including one vector (unlimited or otherwise)
with another. I'd appreciate any leads.
Thanks, Fred
--
Fred Knight | knight@xxxxxxxxxx | 781 981 1053 | fax: 781 981 5359
C-490 | MIT Lincoln Laboratory | 244 Wood Street | Lexington, MA 02173
