Okay.

Okay

so yes.

That is most probably a sign that you have a very old version of a browser.

I know this about Apple tablets

which have kind of fixed browsers

old versions of Safari

on it.

Yeah

the tablets can have a problem

yes.

And I'm afraid there's nothing I can do about it.

Any more questions and comments?

We were talking about informed search.

And you can probably best summarize informed search.

One is you have to have a heuristic.

The heuristic is something that's external to the problem formulation.

And if the heuristic is good

life is easy.

If you have a straight line distance heuristic

past finding is not a problem.

If you do not

you're basically left with iterative deepening search

which is exponential.

So the real problem or the real art is finding good heuristics.

The good news is if you have one, then everything works.

The bad news is there are very few heuristics that work for more than one problem.

Yes

straight line distance works in Romania and in Germany and in India and Russia too.

Not a problem.

Okay?

But that's kind of the exceptional case.

So the question

of course

is how do you find good heuristics?

And we started looking at that.

And we looked at essentially different heuristics than what we came up with was the idea that

we have the best of all heuristics

the true distance or cost to the goal.

And the closer a heuristic comes to that

the more direct the search is.

And in particular, if we have two heuristics and one of them dominates the other, as we

say

then it is actually a better heuristic

meaning less search.

We looked at examples for the nine puzzle

which is essentially we have the Manhattan

distance and the misplies

tile numbers as heuristics

which are