Soar 9.5.0.beta Release Notes, July 2015

This release of Soar includes a new, more powerful version of chunking, which
we call explanation-based chunking. It also includes various important bug
fixes, new commands for semantic memory, a new reinforcement learning

SVS, explanation-based chunking and all other learning mechanisms are off by

And, a special thanks to Alex Turner for his many contributions getting this
release out as well as the new unit and performance testing frameworks, Nathan
Glenn for his Lexer, parser and scons build improvements, and to Soar
Technology for funding a portion of 9.5's development in 2014. Also, a thanks
to Mitchell Bloch for the GQ(λ) Off-Policy Learning option and Steven Jones
for the new semantic memory debugging commands.

Beta Version Information

This version of Soar has has been a research project that has been in parallel
development with main branch of Soar for almost two years. As a result, we
currently consider this version a beta release. Because the changes were
so widespread and involved, we want to spend extra time testing correctness,
optimizing for speed, improving memory use and creating documentation.

That said, it's already being used to do some interesting new work in more than
one big research project at the University of Michigan. Moreover, many of the
low-level changes have been gradually migrated over in 9.3.4 and 9.4.0, so those
aspects have already had a lot of field testing.

Important Changes

(1) Explanation-Based Chunking

Soar is now able to learn rules that are far more general than before.
While previous versions of Soar would only generalize relationships
between Soar short-term identifiers, Soar 9.5's EBC system will now
generalize reasoning over other types of knowledge.

In more practical terms, any element in a learned rule can now be
variablized. To handle the type of reasoning that agents use with
these other knowlege types, Soar will add constraints on the
value of variables which summarize what constraints had to be true
for the original problem-solving to occur.

In general, we expect users to find that:

- Their agents will learn fewer rules that can apply to a greater number
of future situations.
- These rules will be more general but never over-general.
- Note that EBC does not eliminate over-generality that can come from
negatively testing structures in a substate. That remains as the
only source of over-generality.
- Their agents will be far less likely to be slowed down by a large
number of very specific rules that never fire. As a result, we hope
that users will eventually be comfortable always leaving EBC on by


- Agents designed to work well with previous versions of chunking may not
see any improvements, since their problem-solving was designed to revolve
around relationships between short-term identifiers.
- EBC has not been tested with the context-dependent preference set, which
was introduced in 9.3.4. (off by default) Users can still enable
learning search control knowlege (what the CDPS does), but Soar will give
a warning.
- Preliminary testing has shown that Soar 9.5's speed is on par with other
major additions to Soar. (based on TestSoarPerformance and a few tests
in the new Soar performance testing framework).
- While we have already found several way to improve performance, we
have not thoroughly profiled the code to find ways to optimize it. We
expect more improvements in the future.
- Memory usage has not been profiled or optimized at all yet. Currently Soar
9.5 will use more memory than 9.4.
- You cannot turn EBC off in 9.5 beta. While we may add an option to
simulate 9.4's chunking, we are not yet sure whether we can make it
exactly equivalent.

For more information, see Mazin Assanie's presentation slides from the 2015
Soar Workshop.

(2) GQ(λ) Off-Policy Learning

- This reinforcement learning option provides off-policy learning quite
effectively. This is a good approach in cases when agent training
performance is less important than agent execution performance.
- GQ(λ) converges despite irreversible actions and other difficulties
approaching the training goal. Convergence should be guaranteed for
stable environments.


- Should use a lower learning rate
- Might need to tune step-size-parameter
- Computational cost is marginally higher.
- Performance is not guaranteed to dominate Sarsa(λ) or Q(λ), but
convergence should be guaranteed.

For more information, see Mitchell Bloch's presentation slides from the 2015
Soar Workshop.

(3) Three new semantic memory debugging commands
- smem --history
- smem --query
- smem --remove

(4) New semantic memory depth parameter
- Semantic memory retrievals now accept a "depth" parameter with an
integer value.
- Soar will limit retrieval to a wme graph of that height.

(5) Various bug fixes
- Full listing will be included with the official 9.5 release. If you
need to know more now, you can visit our github site and browse the
commit history of the development branch.

(6) Many low-level architectural changes and a lot of code clean-up and
- New test representation
- More object-oriented
- Centralized output manager
- General memory manager that allows memory management to no longer be
- Vastly improved debug output for Soar data structures
- Lots of new unit tests. About 50 of them are new ones created for the
new explanation-based chunking capabilities. We're also in the process
of porting a few hundred unit tests from the java-based version of Soar.
- Eliminated a few third-party libraries Soar that was dependent on
- A new performance testing framework that will allow us to compare a
broader range of agents

General Information

Soar can be downloaded by following the download link on the Soar home
page at:


Soar releases include source code, demo programs, and a number of
applications that serve as examples of how to interface Soar to an
external environment. There is support for integrating Soar with C++,
Java, Tcl and Python applications. Many tools that aid in development
of Soar programs are also available. The download section of the web site
allows you to browse and download all of the
different distributions, tools and agents.

[Help and Contact information]

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