Why don't they riichi?

[or2az]

I have noticed that in one of the games I play which has a multitude of computer opponents to chose from, that some of them will always win their concealed hands by ron or tsumo (quite regularly, I might add), but they will never riichi, and I mean never!
They get the usual assortment; pinfu, iipeiko, CSD, honitsu, seven pairs, straights, etc, etc, but never riichi.
Naturally, they also win with open hands; tanyao, toi-toi, flushes, etc, etc.
I find it hard to believe that there is some sort of strategy to this style of play, (after all, the game is called Riichi Mahjong), but I could be wrong.
The only other thing I can think of is that they are programmed this way to make all of them different in some respects with certain strengths and weaknesses, thus adding some variety to the game for human players of various skill levels, although never hitting the riichi button seems a bit drastic. What do you think?

[Ozball]

Is it a game that bases cpu opponents off of real people?

[or2az]

Not exactly sure what you mean. Are you referring to "actual" people (like me and you) or just people in general, that probably don't exist, like kousuke, ayaka, kazuya, meirin, and bob. And how would I know?

[Ignatius]

I bet some mahjong pros just do not go Riichi, and like to play mostly damaten. Probably that´s why Ozball asked that question. In the game Saikyo Mahjong 3D, for example, each character has it own playing style. A few of them seldom declares Riichi. The playing style of each character can be changed through options.

[jespernohr]

Real people know when to riichi and when not to riichi. It all depends on value, position, what's the score etc.

CPUs are based on rules. Know the rules and you will know exactly how they play

[Ozball]

I bet some mahjong pros just do not go Riichi, and like to play mostly damaten. Probably that´s why Ozball asked that question. In the game Saikyo Mahjong 3D, for example, each character has it own playing style. A few of them seldom declares Riichi. The playing style of each character can be changed through options.

This. MFC also has Pro CPUs, though I don't know how closely they are based off their real life counterparts.

Real people know when to riichi and when not to riichi. It all depends on value, position, what's the score etc.

CPUs are based on rules. Know the rules and you will know exactly how they play

The answer to your question or2az is basically this (and what you said in your OP). They're programmed to never reach, so as to give the human player a different experience. Also different / non-standard styles of play can really throw people off their game (See the whole Horiuchi debacle from last year) so it also adds an extra challenge and means you need to be pretty good at being able to read when your opponent is in tenpai if they are always going to be damaten.

[Masa]

When I played with computer(Super Real Mahjong series) over 20 years ago, The strip mahjong was majority. There were nothing pure mahjong game like MFC or MJ in the arcade.

There was no doubt. That computer was really strong
I spent much coins to see "something"

[or2az]

I have noticed that in one of the games I play which has a multitude of computer opponents to chose from, that some of them will always win their concealed hands by ron or tsumo, but they will never riichi, and I mean never!
I find it hard to believe that there is some sort of strategy to this style of play, but I could be wrong.

Well, I guess I was wrong. There is a strategy to not calling riichi.
After doing a lot of reading on damaten, I found this in Osamuko's blog, which sums it up quite nicely.

"Riichi is an announcement to the whole table that you are Tenpai. It tells everyone that you are a threat and they should take immediate action to defend. If they do, you’ll be winning a whole lot less because everyone is throwing safe tiles at you. However, if there are people who attack recklessly right up to the point where you Riichi, you can use Dama-ten to prevent them from going into defensive mode. This way they’ll keep discarding dangerous tiles and you’ll have a much better chance of getting your winning tile from one of them."

This is what THEY are trying to do to ME. Since I am one of those people who attack right up to the point where someone calls riichi, and then go into defensive mode, they are using damaten to keep me discarding dangerous tiles so they will have a much better chance of winning on one of them. OH, THOSE SNEAKY COMPUTER ROBOTS!

I also found this on the blog;
"If you have a really high-value hand, Dama-ten can be important. You absolutely do NOT want to give away that you are shooting for a monster hand, or opponents will do anything they can to stop you!
If you decide to Dama-ten but tsumokiri everything after that, opponents might get an idea of what you are up to. (Tsumokiri means discarding the tile you just drew.) Make sure you don’t tsumokiri every turn or your cover will be blown!"

My question is, if you don't tsumokiri every turn, how do you maintain your high-value hand?

[Referee]

One possibility is discarding a tile from your hand when you draw a duplicate.

[Ozball]

There is strategy for not declaring Reach, but to NEVER declaring Reach is still extreme. There are times when I personally don't reach (Eg usually hands at Haneman or above that already have a yaku) and the rule set you're playing with will pay a part as well. Eg JPML A rules don't have ippatsu and Ura-Dora so the value of reaching is a lot lower as you'll only ever get 1 han out of it.

Looking for someone tsumogiriing every turn is one way to judge if they are in tenpai or not. The only way to not send this signal is as referee said, if you draw a duplicate of something already in your hand then you can discard the one from your hand to make it look like you're changing things.

[Masa]

if you draw a duplicate of something already in your hand then you can discard the one from your hand to make it look like you're changing things.

This behavior is called "Kara-giri".(and Discarding from hands -> "Tedashi", Tsumo-giri -> already mentioned)