Calculating a par sheet for a multi-line slot is not always as easy as it seems.

Calculating as if for one line only works when there are no weighted symbols.

I'll give an example.

With a single line game, it's possibly to give a lot more weight to the blanks above and below the major jackpot symbol. But if you try this on a multiline game, the results change significantly. let's say the jackpot symbol is weighted at one, with the blanks above and below the line weighted at six. this means the jackpot is 6*6*6 (216) times more likely to land above the winline, and that same number of times it will go below the winline. now you pay 3 coins? there's now 433 chances to get that jackpot, with the same number of possible spins on the virtual reels. even at triple the cost per spin, you get much more back.

If you just do the single line calculation, it will be very wrong for the multiline. In a 3 line slot with weighted blanks, you must put the blanks above and below the major jackpot symbol to the SAME weight as the major to stop them from crowding around the winline.

Now let's say these symbols are also a multiplier of other wins. Oh dear...

This is the case in Triple Triple Diamond 3 line. There are spots on the reels with consecutive blanks. This is to let high value symbols be rare not only on line 1, but also on line 2 and line 3.

Now one silly programmer was making this slot for Masque slots, in a program called IGT Slots Diamond Galaxy. A slots program with "True Casino Odds." He saw the consecutive blanks, and merged them, removing the extra wide spots on the reel, and combining the weights. This completely broke the major jackpot, which with this coding error is 3,150 times more likely to show on line three than line one, which is a 1 in 200 cubed chance.

I was able to decompile the swf, and check the ActionScript to see the weighted reel table. And while most of them were 11 symbols, and 11 blanks, which is what's expected for a 3 reel slot, that one had 10 symbols on reel 1 and 2 with ten blanks, and nine symbols and nine blanks on reel 3. While the math works out anyway for center line wins, lines 2 and 3 were totally screwed up, with the 9x multiplier symbols showing up way too often on lines 2 and 3. Which allows you to make a killing.

they had [kSymBlank,15],[kSymLogo,1],[kSymBlank,1]

for reel 1 and 2.

it should have been

[kSymBlank,14],[kSymBlank,1],[kSymLogo,1],[kSymBlank,1]

now it's equally likely above and below the winline.

So when doing a multi-line slot with weighted reels, you must actually record all wins from each possible spin on all lines on the virtual reels, divide by the number of spins, then divide by the number of credits per spin, THEN multiply by 100 to get the percentage.

As far as I know, this in not mentioned in the guides.

I thought that not having weighted symbols on multi-line slots was the standard, for pretty much exactly the reason stated in the original post.

Quote: ThatDonGuy

I thought that not having weighted symbols on multi-line slots was the standard, for pretty much exactly the reason stated in the original post.
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I think you are basically correct. Most multi-line games are video which have no need for weighted reels. Mechanical multi-reel games still tend to use weighted reels.