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Best of John Robison

Gaming Guru

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Ask the Slot Expert: Should I play more lines on a slot machine or more coins per line?

12 September 2012

John,

Love your column. Always look forward to it, and to your great input. Told my friends about you.

My question is: Are the odds better if you play 100 lines (max) x 2 cents (least), 50 lines x 5 cents, or 25 lines x 10 cents, and so on, on any one machine?

I would appreciate your feedback as I do your wisdom.

Sincerely,
Slot Starvin' Marvin

Dear Marvin,

Thanks for the kind words about my column.

Most multi-line/multi-coin (video) slots are straight multipliers (that means there's no bonus for playing more coins), so the number of coins you bet on a line and the number of lines you play do not affect the long-term payback. When you spread out your bet over more paylines, however, you decrease the volatility you'll experience because you have more ways to win a portion of your bet. The more paylines you play, the lower the volatility and the greater the chance that you'll win something on a spin.

To sum up, your long-term payback is the same, but the hit frequency goes up as you bet more lines and the volatility goes down.

Jackpots for all,
John


John,

I have looked through most of your archives and cannot find a more detailed explanation of how the RNG and lookup tables work in a slot machine. I have a good understanding of the process but a few things about the process I can't put together. Can you fill in the gaps for me?

You press the stop button and the RNG takes a number the "seed" which I understand to be typically based on the milliseconds that have elapsed since 1/1/1970 and divides that number by the number of positions in the virtual reel table, usually 64 or 128. The remainder of that number is used to find the actual stop or reel position on the machine. This system makes complete sense to me (and possibly my system is slightly off). My more important question is if a time "seed" is used and only one pseudo-random number is used how does each reel get assigned a truly random number? My thought process would leave me to believe that all the reels would get the same number picked for them with this process. Even if there was a determined delay in the process of picking random numbers the resulting combinations for reels 2 and 3 would be a result of reel 1. Wouldn't that be great to hit the top prize on the more difficult machines every 128 spins? Can you please explain this process in depth explaining the seed and the RNG's process to determine a number for each reel?

Thanks,
Kris

Dear Kris,

You're missing some very important steps in how the RNG operates.

The RNG is a mathematical function that takes a value, called the seed, performs some mathematical operations on it, and returns a number.

The RNG in a slot machine needs to run continuously, as per slot regulations in all jurisdictions (as far as I know). The RNG also needs an initial seed value. So, here is what happens.

When the slot machine is turned on, the program running the slot needs an initial seed value for the RNG function so it might use the number of milliseconds since 1/1/1970. Then it regularly calls the RNG function (hundreds of times per second), each time passing in the last number generated as the new seed value.

When someone plays the machine, it has to determine the outcome of the spin. Let's start with the first reel. The program gets the most recently generated number (called "polling the RNG"), divides it by the number of virtual stops on reel 1, and then uses the remainder as an index into the virtual reel table for reel 1 to determine which physical stop should land on the payline.

Now the program needs to determine which physical stop should land on the payline for the second reel. It polls the RNG again, divides by the number of virtual stops on reel 2 (which is usually the same as reel 1), and uses the remainder as an index into the virtual reel table for reel 2 to get the physical stop. This process is repeated for the remaining reel(s) on the machine.

With these additional steps, I hope you can see how the machine gets a separate random (well, pseudo-random, really, but that's another subject) number for each reel.

Jackpots for all,
John


Just read your question and answer about taking machines off the floor if they are paying too much. Well, here is my opinion. At my favorite casino in Indiana I have hit it pretty big on 3 slots and have watched 2 others hit a big one. The next month (we go once a month) the machines are gone -- without exception.

When the southern Ohio casinos open I'm switching casinos.

Kentucky slot player

Dear Kentucky,

Machines have to pay their jackpots sometimes. If they didn't, they would be holding too much money. If a casino removed machines every time they had a hot streak, there would be no machines on its slot floor.

I'll never be able to convince you that the disappearance of the machines that paid jackpots is just a coincidence. But you might be able to convince yourself. The next time you see a machine pay off, check to see if it's still there the next time you visit. I bet that the machines will still be there the vast majority of the time.

One more thing to keep in mind. Maybe the machines weren't removed, but just moved.

Jackpots for all,
John

John Robison

John Robison is an expert on slot machines and how to play them. John is a slot and video poker columnist and has written for many of gaming’s leading publications. He holds a master's degree in computer science from the prestigious Stevens Institute of Technology.

You may hear John give his slot and video poker tips live on The Good Times Show, hosted by Rudi Schiffer and Mike Schiffer, which is broadcast from Memphis on KXIQ 1180AM Friday afternoon from from 2PM to 5PM Central Time. John is on the show from 4:30 to 5. You can listen to archives of the show on the web anytime.

Books by John Robison:

The Slot Expert's Guide to Playing Slots
John Robison
John Robison is an expert on slot machines and how to play them. John is a slot and video poker columnist and has written for many of gaming’s leading publications. He holds a master's degree in computer science from the prestigious Stevens Institute of Technology.

You may hear John give his slot and video poker tips live on The Good Times Show, hosted by Rudi Schiffer and Mike Schiffer, which is broadcast from Memphis on KXIQ 1180AM Friday afternoon from from 2PM to 5PM Central Time. John is on the show from 4:30 to 5. You can listen to archives of the show on the web anytime.

Books by John Robison:

The Slot Expert's Guide to Playing Slots