Progressive Contribution

What a great site! I only just noticed it has a forum too..

Anyway I've been coding some free-to-play slot games for my site and I thought it might be fun to have a "progressive jackpot" like the one's they have on some sites.

I want something like:

-must pay out by 1000
-5% from the stake goes to the progressive
-starts at 100

Now I've calculated all my probabilities and returns for my line wins and scatters etc but I'm confused about progressives.

If I have 10 lines and I'm playing on 100 credits (so 10 credits per line) my wins are calculated as credit per line x win amount. So 5 Kings a win of 75 x 10 (credit per line) = 750.

But if I take off 5% contribution to the progressive my maths is all screwed. so my actual spin would be 95 credit and I'd end up with weird win amounts.

They don't seem to be doing it like that on real casino sites so I'm wondering how they are factoring in the progressive contribution into the pays and returns.

Could someone help please?

Determine the payback percentage you want to have the machine set at. A typical one cent games returns around 88%. Set up your paytable and reel weights such that the game pays back 83%. By adding in the 5% of coin in for the progressive the actual return becomes 88%.

Quote: DRich

Determine the payback percentage you want to have the machine set at. A typical one cent games returns around 88%. Set up your paytable and reel weights such that the game pays back 83%. By adding in the 5% of coin in for the progressive the actual return becomes 88%.

In other words, you do pay that dollar. You just pay it 5% less often, because that money is seeding your progressive. At least that's how I understand it. The easy way (I think) would be to remove a paying combo worth about 5% on your paytable, or knock down the value on several a notch. If you pay 4x a winning line for something, pay 3x instead, for example, and count that towards your progressive.

Using the above example, calculate your probabilities to equal the 83% assuming the base amount for the progressive (that's the $100 number you quoted).

Then the 5c per dollar that goes in to the progressive gets you to 88%. This gets you to a progressive that just continues to grow. I'm less clear on a must-hit.

Must-hits don't change anything, they just artificially interrupt the growth of the jackpot by paying it at intervals no greater than the must-hit amount. It still keeps growing at 5% regardless of whether it pays frequently or not.

Quote: beachbumbabs

In other words, you do pay that dollar. You just pay it 5% less often, because that money is seeding your progressive. At least that's how I understand it. The easy way (I think) would be to remove a paying combo worth about 5% on your paytable, or knock down the value on several a notch. If you pay 4x a winning line for something, pay 3x instead, for example, and count that towards your progressive.

That's if you want to work backwards from total RTP including progressive. Usually it's the other way around -- you start with the base RTP and then the progressive rate is configurable and thus so is the total RTP. Most of the time you'll have a handful of base RTPs and then a setting for progressive rate on top of that. You could get to 90% by using the 90% game with no jackpot, or using the 88% game with a 2% jackpot, or the 85% game with a 5% jackpot, etc.

Quote: davidrams

Anyway I've been coding some free-to-play slot games for my site and I thought it might be fun to have a "progressive jackpot" like the one's they have on some sites.

I want something like:

-must pay out by 1000
-5% from the stake goes to the progressive
-starts at 100

Now I've calculated all my probabilities and returns for my line wins and scatters etc but I'm confused about progressives.

For what it's worth, kudos on taking the time to do your progressive math correctly. I did the games for Double Down Interactive but they had a fake progressive jackpot and wouldn't let me fix it. Nobody cared in 2011 though, they were making too much money.

Quote: MathExtremist

That's if you want to work backwards from total RTP including progressive. Usually it's the other way around -- you start with the base RTP and then the progressive rate is configurable and thus so is the total RTP. Most of the time you'll have a handful of base RTPs and then a setting for progressive rate on top of that. You could get to 90% by using the 90% game with no jackpot, or using the 88% game with a 2% jackpot, or the 85% game with a 5% jackpot, etc.

Yeah, I was referring to him trying to reconfigure the paytable he already generated. Your advice on this is better; start over with a target in mind, base RTP, then add your progressive RTP.

Thanks for the great answers guys I think I get some of it now.

I can always adjust my symbol distribution and rerun my probabilities and returns no problem.

So if I did as you suggest and start with say 95% RTP and I want 5% of that to be from the progressive then I just adjust the odds of the progressive until it gives the 5% return roughly. Is that correct?

If so then i'm still slightly confused by the maths since the progressive value increases.

If it was a fixed 1000 credit jackpot then I'd calculate the return by setting the odds at say 20000-1 and multiplying the probability by 1000 which gives me 4.99997% return.

1. Does that make sense?
2. How if it starts at 100 and can go to 1000 how do I make so the odds scale so you have 100% chance by 1000?
3. What does that mean if I wanted to calculate the return? Not sure how to calculate scaling probabilities and returns.

Apologies if anyone already answered this, I may have not understood some of the replies.

Quote: MathExtremist

Must-hits don't change anything, they just artificially interrupt the growth of the jackpot by paying it at intervals no greater than the must-hit amount. It still keeps growing at 5% regardless of whether it pays frequently or not.

Wouldn't must hit increase the return? Say it starts at $100 and must hit by $101. Even if it has a 0.00001% chance of hitting, it MUST be paid at the must hit amount, artificially increasing the hit rate.

Quote: RS

Wouldn't must hit increase the return? Say it starts at $100 and must hit by $101. Even if it has a 0.00001% chance of hitting, it MUST be paid at the must hit amount, artificially increasing the hit rate.

The $100 amount matters, but I usually account for that separately from the $1 (or whatever the jackpot becomes). When you split it out, you get a clean calculation for how much the reset value ($100) contributes to the RTP and then the rest is a straight add-on. There's a bit of circularity in that increasing the accrual rate also increases the hit frequency for a must hit, but it's easy enough to calculate.

On the other hand, while I understand your point, yours was a contrived example. In practice it's often the case that the reset value is low enough (compared to the must-hit amount) that the contribution you're talking about is a negligible fraction of a percentage. In my experience labs often don't catch (or care about) a discrepancy less than 0.001%, and even 0.01% is pretty minor. In the grand scheme of things, that level of precision doesn't really matter to the bottom line -- if a slot game wins $300/day at 8%, the difference in expected win between 8% and 8.001% over a three-year useful life of the game (which is optimistic these days) is only $41; the difference between 8% and 8.01% would be $410. The point is that, certainly for a free-to-play unregulated slot game, I wouldn't put a ton of engineering time into making it exactly perfect. Not when you could spent the money better on user acquisition. That's where the real costs are in social right now.

Hello,

and what about the initial value of the jp. Is it considered in the base RTP of the game? (Taking the situation that jp is triggered by a certain combination only)

Quote: spinswizard

Hello,

and what about the initial value of the jp. Is it considered in the base RTP of the game? (Taking the situation that jp is triggered by a certain combination only)

yes. Any amount over the initial seed amount is player money, contributed by prior spins.