Arc Consistency in Constraint Satisfaction Problems
Dive into the concept of arc consistency in constraint satisfaction problems. Learn how propagation ensures consistency in all arcs within the CSP, and the importance of managing queues for effective problem-solving. Explore examples and illustrations to grasp the concept better.
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Presentation Transcript
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: SA->WA NT->WA NT Q WA SA NSW V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: NT->WA WA->SA NT->SA Q->SA NSW->SA V->SA NT Q WA SA NSW V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: WA->SA NT->SA Q->SA NSW->SA V->SA WA->NT SA->NT Q->NT NT Q WA SA NSW V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: WA->SA NT->SA Q->SA NSW->SA V->SA WA->NT SA->NT Q->NT NT Q WA SA NSW V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: NT->SA Q->SA NSW->SA V->SA WA->NT SA->NT Q->NT NT Q WA SA NSW V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: Q->SA NSW->SA V->SA WA->NT SA->NT Q->NT NT Q WA SA NSW V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: NSW->SA V->SA WA->NT SA->NT Q->NT NT Q WA SA NSW V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: NT NT Q Q WA WA SA SA NSW NSW V V Remember: Delete from the tail!
POLL: What gets added to the Queue? A simple form of propagation makes sure all arcs are consistent: Queue: A: NSW->Q, SA->Q, NT->Q B: Q->NSW, Q->SA, Q->NT NT NT Q Q WA WA SA SA NSW NSW V V
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: NT->Q SA->Q NSW->Q NT NT Q Q WA WA SA SA NSW NSW V V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: SA->Q NSW->Q WA->NT SA->NT Q->NT NT NT Q Q WA WA SA SA NSW NSW V V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: NSW->Q WA->NT SA->NT Q->NT WA->SA NT->SA Q->SA NSW->SA V->SA NT NT Q Q WA WA SA SA NSW NSW V V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: WA->NT SA->NT Q->NT WA->SA NT->SA Q->SA NSW->SA V->SA V->NSW Q->NSW SA->NSW NT NT Q Q WA WA SA SA NSW NSW V V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: WA->NT SA->NT Q->NT WA->SA NT->SA Q->SA NSW->SA V->SA V->NSW Q->NSW SA->NSW NT NT Q Q WA WA SA SA NSW NSW V V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: SA->NT Q->NT WA->SA NT->SA Q->SA NSW->SA V->SA V->NSW Q->NSW SA->NSW NT NT Q Q WA WA SA SA NSW NSW V V Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: SA->NT Q->NT WA->SA NT->SA Q->SA NSW->SA V->SA V->NSW Q->NSW SA->NSW NT NT Q Q WA WA SA SA NSW NSW V V !!! Remember: Delete from the tail!
Arc Consistency of an Entire CSP A simple form of propagation makes sure all arcs are consistent: Queue: SA->NT Q->NT WA->SA NT->SA Q->SA NSW->SA V->SA V->NSW Q->NSW SA->NSW NT NT Q Q WA WA SA SA NSW NSW V V Backtrack on the assignment of Q Arc consistency detects failure earlier than forward checking Can be run as a preprocessor or after each assignment What s the downside of enforcing arc consistency? Remember: Delete from the tail!
