Yochan Research Group

Project: AltAlt System

"A Little of This a Little of That"


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AltAlt system is a domain-independent planner based on a combination of Graphplan and heuristic state space search technology.  The first version of AltAlt competed in the last international planning competition (AIPS-2000). Although that version was not completely debugged, it stayed on the average with respect to the rest of the planners. AltAlt has recently been  enhanced, and its performance with respect to the test suite used in the last AIPS-2000 planning  competition, as well as many benchmark problems is remarkably robust.

AltAlt is a hybrid planner implemented on the top of two state of the art planning systems, STAN a Graphplan-style planner and HSP-r a heuristic search planner. Basically, AltAlt uses Graphplan's planning graph data structure to derive a family of very effective search heuristics, which are then used to drive a heuristic state search planner.

The new version of AltAlt has been enhanced with a variety of optimizations to drive down the cost of heuristic computation, as well as the state search. Specifically, we have use partial constructed planning graphs to control the cost of computing the heuristics, and  subsets of actions in the planning graph to limit the branching factor of regression search.

Slides of a Talk on AltAlt.

Related Publications.

1. Planning Graph as the Basis for deriving Heuristics for Plan Synthesis by State Space and CSP Search.
XuanLong Nguyen, Subbarao Kambhampati and Romeo Sanchez Nigenda. Artificial Intelligence. March 2002. (

2. AltAlt: Combining the advantages of Graphplan and Heuristic State Search.
Romeo Sanchez Nigenda, XuanLong Nguyen and Subbarao Kambhampati. ASU Technical Report   (Postscript) (PDF).

3. Extracting effective and admissible heuristics from the Planning Graph. XuanLong Nguyen and Subbarao Kambhampati. Presented in AAAI-00

4. Distance based goal ordering heuristics for Graphplan Subbarao Kambhampati and Romeo Sanchez Nigenda. In Proc. AIPS-2000.

5. AltAlt-p: Online parallelization of plans with heuristic state search. Romeo Sanchez and Subbarao Kambhampati. ASU CSE TR02-002.


AltAlt source code is available in C/C++ and Common Lisp. The executable code runs under Red Hat Linux 6.0 platform. If you find bugs or have any comments about the source code, please feel free to contact us.The Common Lisp version of the planner is available only upon request.

C/C++ Version. AltAlt1.0

Common Lisp Version. AltAlt


For any comments on the code or discussions about the AltAlt project contact to:

Dr. Subbarao Kambhampati.

Romeo Sanchez Nigenda (C/C++ Version).

XuanLong Nguyen (Common Lisp Version).

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