Identifying Dangerous Suji

Suji are a popular defense strategy; so popular, in fact, that suji traps are an effective anti-defense. We would like to increase the yomi level and create an anti-anti-defense by identifying when suji traps are likely. Are there situations in which suji are more dangerous? Are they really traps, or are they just incidental discards?

Prominent authors actually disagree on this. Some claim that suji discarded after riichi are more dangerous, while others claim that suji discarded before riichi are more dangerous. The general agreement is that the tile discarded immediately upon declaring riichi is dangerous.

Who’s right? Do you think there’s a difference? Using the Tenhou game logs database, we can examine riichi hands and their discards to finally answer this question.

(more…)

I told you not to go for Kokushi

We’ve all been there: you’re dealt a hand with a lot of yaochuu tiles — ones, nines, and characters — and you find yourself asking, “Do I go for the stupid thing?”

Despite being one of the most common yakuman, Kokushi Musou still boasts a wide arsenal of ways to betray you. Those last few tiles never seem to come; your discards give away your strategy; you have no real defense; and if the other players discard all four of a tile you need, you can’t easily switch to something else.

So when do you go for it? An advanced player might say that you can do it when you start with 11 different yaochuu tiles, but if you’re playing a 3-player game on Tenhou, you can do it with 8. Aside from that, are there any situations in which it’s worth being more aggressive? Are there any strategic uses for the forced redeal (kyuushukyuuhai)? In this post, I will look at the strategies employed by players when they had the chance to go for Kokushi. What choice did they make? Were they successful? What situational information influences the decision to be more or less aggressive?

(more…)

Statistics: The Value of a Lead

After I started playing mahjong, I learned one thing very fast. It is great to be in the lead. It’s not just great. It is amazingly awesome. You are like a champion looking down on the rabble, watching them scrabble around for crumbs from your table, more often than not having to cannibalize each other to stay ahead. When a minor threat emerges, you can just put on your defensive armor and snicker at the pathetic attempts at toppling you. Should you choose to take the offensive, you can strike from anywhere, at anyone, with anything. Or if you are rich and bored you can just take a luxurious stroll around menzen mansion and not do much of anything, while everyone else is hanging on your every discard, safe in the knowledge that even doing absolutely nothing can benefit you. Being in the lead is great. But how great is it?

(more…)

Yaku defense guide: Toitoi and Yakuhai

Well hello there. It seems that some strategy for defending against specific yaku is in order here! Today, I shall discuss some ways to fight back against THEM TOITOIS, as well as those “yakuhai + rage” hands people complain about.

If you’ve been playing Mahjong for a while then you probably know of some environments where these yaku feature very prominently in the play style. Are you frustrated? This post will be intended to help people, not to criticise them, so we won’t be complaining about this or that ruleset, environment, or whatever. Rather, we’ll come up with ways to counterattack the people who take advantage of the opportunity afforded by the rules to cheapen the game.

Also, you might have heard some yaku counterattack strategy already, but only in cases where it is treated very briefly. Thanks to our extensive statistical research tools, I hope we will be able to go a bit more in-depth when looking at what our opponents are doing, and see how this compares with theories we have heard.

(more…)

Let’s Debunk Some Mahjong Superstitions!

Hey, this is UmaiKeiki, a very lazy mahjong player — although I’m often in the company of some real addicts. They’ve scoured the internet for anything and everything related to Mahjong, and found some really outrageous ideas. Are the tiles given by Tenhou really random? Is a hanchan really the same length as two tonpuusen? Questions like these, while not exactly about “luck” and the “flow of the game”, are a bit reminiscent of “occult” Mahjong, which is essentially the belief that random events in Mahjong are not really random.

Now there’s nothing terribly wrong with Occult Mahjong in that it can be a convenient way to explain away some minor issues — such as that awful losing streak you just had, or some secret technique you don’t want to share with everyone. However, it sure would be fun to test some of these claims against the mathematics of probability and statistics! Today we shall do exactly this, and see how well they stand up.

(more…)