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SYNOPSIS:
GRESS (Gradient-Enhanced
Software System) automates the implementation of
direct and adjoint sensitivity analysis methods into
existing FORTRAN models.
WHOM TO CONTACT:
Jim Horwedel
Nuclear Engineering Applications
Computing Applications Division
Oak Ridge National Laboratory
P. O. Box 2008
Oak Ridge, TN 37831-6370
Tel.: (615) 576-4420
Fax: (615) 574-3527
jqh@ornl.gov
DOCUMENTATION:
- WWW:
- papers:
- J. E. Horwedel, GRESS Version 2.0 User's
Manual, ORNL/TM-11951 (November 1991).
- J. E. Horwedel, GRESS,
A Preprocessor for Sensitivity Studies of Fortran Programs, Proc. of
SIAM Workshop of Automatic Differentiation of Algorithms: Theory,
Implementation, and Application, Breckenridge, Colorado, January 6--8,
1991, pp. 243--250 (1991).
- B. A. Worley, Experience with the
Forward and Reverse Mode of GRESS in Contaminant Transport Modeling
and Other Applications, Proc. of SIAM Workshop on Automatic
Differentiation of Algorithms: Theory, Implementation, and
Application, Breckenridge, Colorado, January 6--8, 1991, pp. 307--314
(1991).
FUNCTIONALITY:
GRESS reads an existing Fortran code
as input and produces an enhanced Fortran code as output.
The enhanced code has additional new lines of coding for calculating
derivative information analytically but using the rules of
calculus. The enhanced model reproduces the reference model
calculations and has the additional capability to compute derivatives
and sensitivities specified by the user. The user also specifies
whether the direct or adjoint method is to be used in computing
sensitivities.
HIGHLIGHTS:
The direct method is
most efficient for applications in which the sensitivities are desired
for a large number of model results with respect to a small number of
model inputs. The adjoint method is most efficient for applications in
which the sensitivities are needed for a small number of model results
with respect to a large number of model input parameters. The
sensitivities can be calculated for any model variable with respect to
any other model variable, so that GRESS can also be used for purposes
other than sensitivity analysis, such as optimization and code
development.
GRESS has been used to enhance large-scale codes for
a wide range of applications, for example,
- 3-D finite
difference transient geohydrology code SWENT was enhanced to calculate
the derivatives of approximately 900 output parameters with respect to
a selection of input variables.
- Shallow-land waste disposal
model PRESTO-II was enhanced for adjoint capability in order to
calculate the derivatives and sensitivities of a few key parameters
with respect to 69,000 data variables.
AVAILABILITY:
The latest version of GRESS operates on the full range of most workstations and
mainframes. GRESS can be obtained from the Radiation Shielding Information
Center, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6362
(615/574-6176).
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