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← 08-02 Problem Solving Vs Planning

Unit 8 2 Problem Solving vs Planning

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Showing Revision 1 created 11/28/2012 by Amara Bot.

  1. [Narrator] You remember our problem-solving work?
  2. We have a state space like this, and
  3. we're given a start space and
  4. a goal to reach,
  5. and then we'd search for a path
  6. to find that goal, and maybe we find
  7. this path.
  8. Now the way a problem-solving agent
  9. would work is first it does all the work
  10. to figure out the path to the goal
  11. just doing by thinking,
  12. and then it starts to execute that path
  13. to drive or walk, however you want to get there,
  14. from the start state to the end state,
  15. but think about what would happen
  16. if you did that in real life; if you did all
  17. your planning ahead of time, you had the complete goal,
  18. and then without interacting with the world,
  19. without sensing it at all,
  20. you started to execute that path.
  21. Well this has, in fact, been studied.
  22. People have gone out and
  23. blindfolded walkers, put them in a field
  24. and told them to walk in a straight line,
  25. and the results are not pretty.
  26. Here are the GPS tracks to prove it.
  27. So we take a hiker, we put him at a
  28. start location, say here,
  29. and we blindfold him so that he can't
  30. see anything in the horizon,
  31. but just has enough to see his or her feet
  32. so that they won't stumble over something,
  33. and tell them execute the plan of going forward.
  34. Put one foot in front of each other and walk forward in a straight line,
  35. and these are the typical paths we see.
  36. They start out going straight for awhile
  37. but then go in loop de loops
  38. and end up not at a straight path at all.
  39. These ones over here, starting in this location,
  40. are even more convoluted.
  41. They get going straight for a little bit
  42. and then go in very tight loops.
  43. So people are incapable of walking a straight line
  44. without any feedback from the environment.
  45. Now here on this yellow path, this one did much better,
  46. and why was that?
  47. Well it's because these paths were on overcast days,
  48. and so there was no input to make sense of.
  49. Whereas on this path was on a very sunny day,
  50. and so even though the hiker couldn't
  51. see farther than a few feet in front of him,
  52. he could see shadows and say,
  53. "As long as I keep the shadows pointing in the right direction then
  54. I can go in a relatively straight line."
  55. So the moral is we need some feedback from the environment.
  56. We can't just plan ahead and come up with a whole plan.
  57. We've got to interleave planning
  58. and executing.