Random Number Generators

Quote: kp

Is the tie breaking done before or after the conversion to integers?

Update	shuffle
Set	sortorder = x.sortorder
From (	Select	shuffle_num,
		c_index,
		row_number() over(order by sortorder) sortorder
			From	shuffle
			Where	shuffle_num = @l_shuffle_num ) x
	Inner Join	shuffle y
	On	x.shuffle_num = y.shuffle_num
		And x.c_index = y.c_index

Quote: s2dbaker

Here's the geekery:

Quote: s2dbaker

For a deck of cards, it gets complicated so what I do is let the RNG assign a value from zero up to but not including one to each "card" in my virtual deck. I then sort the cards by the number assigned and turn those numbers into Integers from one to 52 ( or 53 with a joker ) because integers are conceptually easier to work with. In the case of a tie, the database decides the order based on the primary key so the Two of Clubs will always come before the Ace of Spades. But with granularity into the trillions, that's a risk I'm willing to accept.

Quote: DJTeddyBear

Out of curiosity, what language is that?

Quote: MathExtremist

Why are you using integer conversions for the RNG values? With this shuffle algorithm, I don't think you need to convert at all. If you have a table with two columns, A for cards and B for floats, then you just randomly assign the float values in column B, sort on it, and A is now your shuffled deck. On initialization you need to assign 0..51 to column A, but only once (not each time). The only thing you need to do for a new shuffle is re-enter floats for column B and re-sort. Then just use a DB cursor to deal the cards.

Quote: MathExtremist

200,000 shuffles per second using C#

Quote: s2dbaker

Wow, no love here for the the SQL! I find it to be very flexible. I can make changes to stored procs while processes that use them are running and do a whole lot of programming no-nos in the interest of reduced development time. It's worth the trade-off just so that I don't have to compile :)