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Tile Efficiency 101 (Part 3)

Part 3 of the Tile Efficiency series for Osamuko.com is here. This time, it's taatsu theory. More precisely? Ryankan.

I skipped a few parts of things you should already know. If you don't, then read:

Tiles from 3 to 7 are the most flexible. 2's and 8's are a little less flexible. 1's and 9's are the least effective of number tiles. And lastly, character tiles/honors are the most difficult of all to complete melds with.

A kanchan (central wait) is superior to a penchan (side wait). That is because a 46 kanchan, for example, can become ryanmen with a 3 or a 7, while a 12 penchan must first draw a 4 and discard the 1, then draw a 5 to have a ryanmen; you're more likely to complete the meld than you are of upgrading the shape.

Also, a kanchan composed purely of tiles from 3 to 7 are superior to other kanchan, because they can expand towards either side (thusly, a 35 kanchan is superior to a 13 or 24 kanchan).

Furthermore, if you have two ryanmen overlapped (23 56) it's less efficient than having two separate ryanmen in two different suits. This is, because if they share an out in common, the number of useful tiles is decreased. Saying "Oh, but I might get a three sided with if I draw the 4 for a 23456!" is no excuse if you have more efficient shapes available. When the same out is repeated for two different taatsu (proto-melds), this is called a "ni-do-uke" (or "double out").


So, if that is clear, then let's continue. This is the source: http://beginners.biz/h_05.html

Taatsu Theory

About ryankan (aka double gut shot).

Ryankan is a compound shape of two kanchan waits, such as 2m4m6m.

The ukeire is of 8 tiles, but...

  1. It uses up 3 tiles.

  2. If it is left as the final wait, it will become a kanchan.

Considering the two points above, it is clear it is less efficient than a ryanmen.

1.Ryankan and Shanpon

Ex1

1m3m3m5m3p3p7p8p1s2s3s6s7s Tsumo: 5s

What becomes a problem with ryankan, is the decission of choosing shanpon over it or not.

In example 1, if we were considering the chances of becoming pinfu, discarding 3m would be correct. Drawing 2m4m it becomes pinfu. Likewise, by discarding 1m or 5m, there is only 1 type of tile that will give us pinfu. Therefore, it may look better to use the ryankan.

However, if we were considering tenpai chance, you should discard 1m with this hand.

Drawing 6m2p4p it perfectly evolves to a smooth 1shanten for pinfu.

3m3m5m3p3p7p8p1s2s3s5s6s7s Tsumo: 2p

In the case of chunchan tiles (simples, middles, tan yao tiles, 2-8) that can evolve to ryanmen, choosing the shanpon+kanchan shape which has better room for hand evolution is generally more advantageous.

Ex2

4m5m6m6m4p6p8p8p4s5s5s6s7s Tsumo: 3m

San Shoku is visible, so we may want to discard 8p but, discarding the 4p that leaves room for the 3menchan (3-sided-wait) in the manzu (cracks/reds) tiles is an excellent discard.

3m4m5m6m6m6p8p8p4s5s5s6s7s Tsumo: 7m

Ex3

1s1s3s5s8s8s4p6p7p8p (pon) 5z5z5z Tsumo: 2p

In the case of an open hand, taking the shanpon becomes more useful.

In example 3, we should cut 5s and aim for the pon-ten (pon and tenpai) of 1s and 8s.

Discarding 1s the uke-ire number doesn't change, however the speed of tenpai is different. That is because you can only call a chii from the player on your left, but you can call a pon from anyone.

Ex4

4m6m8m8m1p1p5p6p7p7p8p3s5s Tsumo: 4s

So, we basically said that is is generally better to take shanpon over kanchan, but this is not so black-and-white.

In example 4, we want to take the better 1shanten shape by discarding 8m. Not just because of the 3m, the backfire of drawing 1p also becomes useful.

4m6m8m1p1p5p6p7p7p8p3s4s5s Tsumo: 1p

By discarding 8m or 4m here, the uke-ire number is greatly increased.

Furthermore, if we discaded 4m to fixate on the shanpon, drawing 5m isn't any useful at all. It becomes nothing more than a complete backfire.

Theory

In a hand with a ryankan, when deciding whether to take shanpon or kanchan, we compare the number of tiles of evolution towards good shape.

Generally, there are many cases where shanpon is better.

2.Ryankan that are easy to overlook

Since ryankan that are embedded inside of melds are easy to overlook, let's be careful.

Ex5

4m5m7m5p5p6p7p7p1s3s3s7s8s Tsumo: 9p

With a hand of a shape such as example 5's, there are people who easily tsumo-kiri (tsumo-kill/discard upon picking up) the 9p.

We can see the ii-pei-kou, but if we extract the 5p6p7p meld, we can see we have a 5p7p9p ryankan in the pinzu (circles/dots).

If we discard the 9p here, we eliminate the 8p uke-ire completely.

Ex6

1m2m2m3m4m6m7m8m9m5s5s6s7s

In example 6, we're one away from ittsuu (full straight), but we have a ryankan in the manzu.

Even if we draw a safe tile, by descarding 2m we are completely missing the chance of tenpai by drawing 3m.

3.Irregular kanchan

Rarely, we come into shapes that are "distant ryankan."

With a shape like

2s4s5s6s7s9s

we have an uke-ire of 8 tiles by using up 6 tiles.

Ex7

4m5m5m6m1p3p4p5p6p8p9p7s7s Tsumo: 6m

You may run many times in cases like this where you must take appart the ittsuu.

Of course we should aim for mentanpin (riichi tan yao pinfu) and iipeikou, but between discarding 1p and 9p there's a huge difference. If we discard the 1p, we completely lose the uke-ire for 2p.

4m5m5m6m6m1p3p4p5p6p8p7s7s Tsumo: 2p

4m5m5m6m6m3p4p5p6p8p9p7s7s Tsumo: 2p


Okay, so that's it for now. You may have noticed the importance of "backfire follow-up" or "urame follow-up." Many times you make a decission, a backfire may happen. Before discarding, think about what becomes a loss, and how will you deal with that loss. Did it ever happen to you that you ended up picking up and discarding a whole series of tiles in a spiral because of one single early discard? Then you're clearly not looking out for your backfires.

Also, sorry I took so long to finish this one up. It was my birthday last week, and yeah, stuff.

See you next time.

Tile Efficiency 101 (Part 3)
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