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Colleagues,
We wish to inform you that ASCEND IV is now available as an
installable binary for Windows (NT4.0,Win95) or as easily
configurable source code for virtually all UNIX platforms.
ASCEND IV is a free, large-scale, equation-based, environment
featuring a strongly-typed, object-oriented model-description
language. ASCEND is designed to reduce the time needed for
creating, debugging, and solving mathematical models by orders of
magnitude in comparison with C++-like and FORTRAN-like languages.
More information on how to obtain this free software can be found
at
here.
in the download section, and we invite you to try it out.
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Why might you want to use ASCEND?
In the past, ASCEND has been targeted to expert model developers
only. ASCEND IV sets out to change that, to bring lessons in
good modeling practice within the reach of engineers and
students. ASCEND IV has several new features, the most important
being that it is extensively documented. The remainder of this
note highlights ASCEND features.
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A list of important
features ASCEND IV continues to support:
Interactive support tools for modeling, debugging, and solving
systems with tens of thousands of nonlinear algebraic or
differential equations. Including:
- a library of equilibrium-based unit operations for chemical
engineering and an easily extensible physical properties
library with thirty-four common species.
- user-centered structured methodology for reaching correct
problem specifications.
- automatic analysis of degrees of freedom.
- automatic checking of unit conversions on input data and
equations.
- automatic initialization of variables.
- choice of automatic scaling methods for nonlinear equations.
- an object-oriented modeling language.
- GNU Licensed source code for all distributed system
components.
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List of features new
in release 0.8:
The interface has been ported to Tcl/Tk 8.0, resulting in a
sharper look and feel as well as Windows compatibility. Tk 8.0 is
very new, so we particularly invite your comments on the Windows
version.
Full documentation. A 235 page book available free with the
software describes the interface and the modeling language
syntax. This book is also browsable on the web from the
Documentation section of ascend.
The language has been modestly expanded as defined in recent
theses and technical reports from Arthur Westerberg's ASCEND
research group in the ICES/Engineering Design Research Center at
Carnegie Mellon. One or two of the minor defined features, for
example a tabular data statement, remain unimplemented. The
documentation clearly notes which features are not yet available.
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New language elements
include:
- a highly reusable library of equilibrium-based unit
operations.
- model construction by object-passing and value passing,
including strict assertion checking to assure valid MODEL
usage in each application context. This vastly improves
compiler performance and diagnostics, also.
- a MODEL preprocessor which very carefully diagnoses errors
and symptoms of poor object-oriented style. Users report that
this preprocessor drastically reduces the time needed to
debug new or complicated models.
- a SELECT statement for choosing among alternative
constructions at instantiation time.
- a WHEN statement for choosing alternative equation sets or
alternative sub-models from available superstructures during
solution.
- a SWITCH statement for managing flow of control in executing
ASCEND methods.
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New solver features
include:
- selection of equations and models based on logical, integer,
or symbolic configuration variables.
- fast automatic analysis of model hierarchies to determine
good reordering of equations and variables to obtain fast
linear factorization.
- an interface to CONOPT, a very good NLP optimization package.
(Sorry, we only distribute the connection to CONOPT -- we are
not licensed to distribute CONOPT itself.) Contact Arne Drud
to obtain CONOPT. UNIX users can build ASCEND with it simply
by pointing at the CONOPT binary library during ASCEND
configuration. The CONOPT/VC++ interface on the PC is still
in development. When a CONOPT DLL becomes available, we will
support its use in a future ASCEND release.
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New interface
features include:
- improved generation of GAMS code for access to out-of-core
solvers and optimizers.
- an object-oriented approach to modeling
differential-algebraic equations, which allows one model to
be used for steady state or dynamic simulation of a process
or of any of its process units (sub-models).
- more intuitive simulation construction and object browsing/
manipulation.
- interactive configuration of window appearance (fonts, etc).
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>end
pitch<
Thank
you.
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