[RESOLVED] Semi-Random file selector.

Weighted Random File Selector.
I am planning out a program with several parts. I have used VB as a hobby for a few years but want to do this in C#. I’m not quit up on what should be a module, a sub-routine or what should be a class. Anyway this is part of what I want to do.

Perhaps from a comma delimited text file, a sub-routine would read in or index a list of files that also have a percentage rating associated with each one.
When called, the program would select one file from the list in a weighted random fashion. In other words the file that had a rating of 10 % should come up approximately ten times as often as the file with a rating of 1 % but not in a predicable way.

Would this be just a little code or a lot?

IIRC modules are a VB specific thing. Next, in .NET we have config files to store dynamic data, a perferred method over using a comma delimited file. And to answer your question, that shouldn't take much code.

The simplest thing to do would be to create a little struct that ties a string (the filename) to a float (the percentage, expressed as a value between 0 and 1).

Code:

---

struct FileWeight
{
  private string _path = "";
  private float _weight = 0.0f;

//put public accessors here...
}

---

Then all you need to do is create one of those for each file in your list, assign a weight to it.

Then once you've got them all in an array (or a list or whatever), just generate a random float in the range zero to (sum of all weights in list).

Then loop through the list adding each weight to a sum until the random float is less than the sum. Then you know you've selected the file by its weight.

20 lines of code max.

:)

How about creating a string array where each filename was in the array x% of the time, and use random to index the array?

Quote:

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Originally Posted by wild_bill

How about creating a string array where each filename was in the array x% of the time, and use random to index the array?

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Because that would be...

a) wasteful of memory
b) fiddly to tune for correct weightedness
c) the resolution would be too low.

Addendum to post #3...

Actually, the weight inside each struct item doesn't have to be between 0 and 1 really, it can be any number. I suggested 0-1 as it might be simpler to deal with.

Just thought I'd better point that out in case you had any problems restraining the values.