From: ccm@sage.cgd.ucar.EDU (CCM Group Directories)
Message-Id: <199405121429.IAA18525@grub.cgd.ucar.edu>
Subject: Operating System change
To: ccm-users@ncar.UCAR.EDU
Date: Thu, 12 May 94 8:29:19 MDT
CCM Users Group:
With the move to Unicos 8.0 at NCAR on Monday, May 9, results from
earlier integrations of the CCM2 Model will no longer be reproducible
bit-for-bit. This is due to a change in the compiler which was used
to generate the object code for the ecmfft library, and changes in the
default math libraries. The new ecmfft library has been tested where
the results agree to approximately 13 decimal places when compared to
results from the previous library (presumably, the result of
instruction reordering by the new compiler). This change produces
machine accurate differences in the CCM2 on the first time step when
compared to the same result generated prior to Monday, May 9th.
The NCAR Scientific Computing Division (SCD) has agreed to make the
old fft library available under the name ecmfft.old for an indefinite
(but likely finite) period of time. The provision of the old library
is to allow users to reproduce the results from earlier CCM2 control
runs, as well from their own model integrations conducted prior to May
9th. The user must also include the old Cray math library "libmv1" on
the segldr command as follows (using libmv1 also causes the Model to
run considerably faster than with the current default math library):
segldr -f indef -o ccm.xx.$$ ccm2.$$.o \
-L /usr/local/lib,/lib,/usr/lib,/ccm/ccm2/T42 \
-l ncaro,ecmfft.old,mv1,net,mss,ccm \
-M ,s
We strongly urge users move to the default libraries as soon as
possible since we are unable to guarantee how long the old fft and
math libraries will be available.
Also as a result of the operating system change, it is necessary to
make a change in the "assign" commands for SSD units found in the CCM2
run script. This change has been made in the Cray permanent disk
copies of CCM2 and CCM2.1 run scripts, and will be included in a new
ftp release, coming very soon.
CCM Core Group