Pathologically Eclectic Rubbish Lister PerlMonks

### comment on

 Need Help??
Cool program!

The evolution of the score you see is pretty typical of genetic algorithms and genetic programs: much progress is made in the initial iterations, but it takes a lot more to gain further improvement.

I just wanted to mention that the assertion by ff's professor that you only need 30 tries is patently false. If a problem has many degrees of freedon and a complex error surface, in general the amount of searching one must do is O(k^N), where N is the number of degrees of freedom and k is related to the complexity of the error surface.

To see this, consider a simple example. Suppose we one have degree of freedom and we know that a good solution lies either at x = -1 or x = 1. Then we only have to search twice. Now add a similar degree of freedon y that interacts with x in a complex way. Then we would need to search (+-1, +-1), or 4 attempts. Adding another would need 8 attempts, and so on, yielding O(2^N) behavior. An this is just looking for a good quadrant! This blowup of search space with degrees of freedom is called the 'curse of dimensionality' and along with a complex error surface, is the basic reason that some problems are NP-complete.

Some problems have some nice large scale structure of the error surface that admit heurisitic guesses that often do well, but others, like k-satisfiability for k > 2, don't seem to. So don't throw away your simulated annealing and genetic algorithms code yet!

-Mark

In reply to Re: Evolution in Action. by kvale
in thread Evolution in Action. by BrowserUk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.

Create A New User
Domain Nodelet?
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others lurking in the Monastery: (1)
As of 2023-01-28 04:31 GMT
Sections?
Information?
Find Nodes?
Leftovers?
Voting Booth?

No recent polls found

Notices?