1 / 15

Review Test1

Review Test1. Robotics & Future Technology. Future of Intelligent Systems. Ray Kurzweil futurist A Long Bet Robot Soccer BBC News - What happened to the Robotic Age ? Robotic Dance?. CHAPTER 5. REVIEW of some important concepts to remember….

ramona-may
Télécharger la présentation

Review Test1

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Review Test1

  2. Robotics & Future Technology

  3. Future of Intelligent Systems • Ray Kurzweilfuturist • A Long Bet • Robot Soccer • BBC News - What happened to the Robotic Age? • Robotic Dance?

  4. CHAPTER 5 REVIEW of some important concepts to remember…

  5. Incremental Problem Formulation (The N-Queens Problem)

  6. Constraint Satisfaction A constraint satisfaction problem (CSP) is a problem composed of variables and constraints. The objective is to assign values to variable in such a way that all of the constraints are satisfied. A CSP can be more formally viewed as a triple <D,X,C> where: • D represents a set of n domains • X represents a set of n variables, each variable xi takes it value from Di • C represents a set of constraints.

  7. Two types of CSPs • Finite domain CSPs • Queens, Domains, Boolean • Infinite Domain CSPs • If Job1 takes 5 days, then Job3 will start • Job1 +5 < Job3

  8. thrashing Wasteful” backtracking is known as

  9. Variable & Value Ordering • Variable order selection seldom results in the most efficient search • One efficient strategy • Minimum Remaining Value (MRV) which chooses the value with the fewest legal values • A.K.A “Most Constrained Value” • A.K.A “Fail-First” Heuristic because it is the most likely to cause failure first

  10. Propagating through constraints • Forward Checking is a better use of constraints • When every variable X is assigned, the forward checking process looks at each unassigned variable Y AND Deletes from Y’s domain any value that is inconsistent with the value chosen for X. • Think of Forward Checking as a way to incrementally compute the info needed for MRV to do its job

  11. Arc Consistency • nother backtrack-based algorithm that is even more efficient is called the maintaining arc consistency (MAC) algorithm. • Arc Consistency provides fast method of constraint propagation stronger than forward checking. • Arc Consistency can be provided as preprocessing step (just as forward checking can be used to preprocess).

  12. MAC Algorithm p146 • Rather than just revising each domain corresponding with the value of each instantiated variable MAC makes the network arc-consistent with respect to the instantiated variables (all arcs must be consistent). • MAC is applied repeatedly until no more inconsistencies remain. • Node Consistency • 1- consistency means that each individual variable by itself is consistent (node consistency) • 2- consistency is arc consistency • 3- consistency means that any pair of adjacent variables can always be extended to a third neighboring variable (i.e. path consistency or AC-3) • AC-3 uses a queue to keep track of nodes that need to be checked for inconsistency

  13. Intelligent backtracking: looking backward • Chronological backtracking: a policy for when a branch of the search fails by backing up to the preceding variable and try a different value for it • Chronological uses the more recent decision point to revisit

  14. Things that cause a failure • The conflict set • Backjumping backtracks to the most recent variable in the conflict set

More Related