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lds revisited

lds revisited. (aka chinese whispers). Send reinforcements. We’re going to advance. Send three and fourpence. We’re going to a dance!. Motivation (rooted in footnote 279/1998) lds (improved) for non-binary domains present the algorithm how does it perform. Quick Intro. A refresher

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lds revisited

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  1. lds revisited (aka chinese whispers)

  2. Send reinforcements. We’re going to advance.

  3. Send three and fourpence. We’re going to a dance!

  4. Motivation (rooted in footnote 279/1998) • lds (improved) for non-binary domains • present the algorithm • how does it perform

  5. Quick Intro • A refresher • Chronological Backtracking (BT) • what’s that then? • when/why do we need it? • Limited Discrepancy Search (lds) • what’s that then Then the story

  6. An example problem (to show bt) 1 2 3 4 5 Colour each of the 5 nodes, such that if they are adjacent, they take different colours

  7. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 v1 v2 v3 v4 v5 4 5

  8. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 v1 v2 v3 v4 v5 4 5

  9. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 v1 v2 v3 v4 v5 4 5

  10. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 v1 v2 v3 v4 v5 4 5

  11. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 v1 v2 v3 v4 v5 4 5

  12. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 v1 v2 v3 v4 v5 4 5

  13. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 5 4 v1 v2 v3 v4 v5

  14. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 5 4 v1 v2 v3 v4 v5

  15. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 5 4 v1 v2 v3 v4 v5

  16. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 5 4 v1 v2 v3 v4 v5

  17. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 5 4 v1 v2 v3 v4 v5

  18. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 5 4 v1 v2 v3 v4 v5

  19. A Tree Trace of BT (assume domain ordered {R,B,G}) 1 2 3 5 4 v1 v2 v3 v4 v5

  20. LDS • show the search process • assume binary branching • assume we have 4 variables only

  21. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take no discrepancies (go with the heuristic) What’s a heuristic

  22. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take no discrepancies

  23. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take no discrepancies

  24. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take no discrepancies

  25. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  26. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  27. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  28. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  29. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  30. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  31. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  32. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  33. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  34. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  35. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  36. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 1 discrepancy

  37. Now take 2 discrepancies

  38. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 2 discrepancies

  39. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 2 discrepancies

  40. Limited Discrepancy Search (LDS) Ginsberg & Harvey Take 2 discrepancies

  41. And now for the Chinese whispers

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