Source: http://blog.jpmahjong.net/read.php/621.htm
Lastly, we'll have an example to end this.
[The image with the K-ON background.]
In this situation, we're the dealer and the round is Ton 4 of a hanchan. We reached tenpai very early, and there are many choices to deal with this.
You can discard 2,3 pin and be in damaten/riichi or discard chun and declare riichi, but there is only one answer.
Damaten on the dora 3 pin might not be an easy wait either.
In addition, you should give up how the intermediate games' players think, like discarding 3 pin and declaring riichi to lure out 2 pin.
There are only two 2 pin left, the chances of winning is slim. Added to the fact that it is next to the dora, there is no one who would fall for such tricks in Houou level games.
You should only set traps when the chances of tsumo is low.
Discarding 2 pin and declaring riichi and tanki on the dora to bet on a tsumo is an extreme method. Tsumo gives you haneman and ura-dora gives you baiman.
If this is all last and you're behind by alot, you can play this way.
But in this situation, a tsumo mangan is more than enough.
Discarding chun here and declaring riichi should only be limited to this hand.
It's early and the chances of tsumo 1/4 pin is high.
And there's also a chance of having ura-dora 1 and reaching haneman.
(But in the actual situation, the other players all went into betaori after the riichi. orz)
Showing posts with label Riichi Theory. Show all posts
Showing posts with label Riichi Theory. Show all posts
Wednesday, 21 March 2012
Sunday, 18 March 2012
Riichi theory(7): Decision between tenpai with points difference - Part 2
There's only one part left after this...
Source: http://blog.jpmahjong.net/read.php/621.htm
Hands with a difference of 2 han
Discarding 7 sou here will not give you pinfu and there's a 2 han difference between the good shape and the bad shape.
In this kind of situation, the key here is the amount of dora that you have.
You have no dora
The riichi with the good shape is only worth 1300 points, whereas the riichi with the bad shape is four times of that, therefore it is better. Without any dora, declaring riichi with the bad shape is the basics.
You have one dora(or there are other yaku worth 1 han, like tanyao)
A damaten with a bad shape(5200), riichi with a good shape(2600) and riichi with a bad shape(8000) are all possible choices. To make a decision, you'll have to look at the points situation here.
In a situation where the points are even, most people will declare riichi with a good shape. Even though damaten is worth twice that of riichi, but if you factor in ura-dora and various other advantages, I feel that riichi is a better choice, especially when you're waiting for number tiles like 3 and 7.
If you're after security, or if you're in the lead, you can choose to stay in damaten. This will give you the possibility of going into betaori.
If it's close to the end of the game and you need tsumo haneman for gyakuten, declaring riichi with a bad shape can be a possible solution.
You have three dora
If riichi and damaten are both worth mangan, declaring riichi with a good shape is obviously better.
Source: http://blog.jpmahjong.net/read.php/621.htm
Hands with a difference of 2 han
Discarding 7 sou here will not give you pinfu and there's a 2 han difference between the good shape and the bad shape.
In this kind of situation, the key here is the amount of dora that you have.
You have no dora
The riichi with the good shape is only worth 1300 points, whereas the riichi with the bad shape is four times of that, therefore it is better. Without any dora, declaring riichi with the bad shape is the basics.
You have one dora(or there are other yaku worth 1 han, like tanyao)
A damaten with a bad shape(5200), riichi with a good shape(2600) and riichi with a bad shape(8000) are all possible choices. To make a decision, you'll have to look at the points situation here.
In a situation where the points are even, most people will declare riichi with a good shape. Even though damaten is worth twice that of riichi, but if you factor in ura-dora and various other advantages, I feel that riichi is a better choice, especially when you're waiting for number tiles like 3 and 7.
If you're after security, or if you're in the lead, you can choose to stay in damaten. This will give you the possibility of going into betaori.
If it's close to the end of the game and you need tsumo haneman for gyakuten, declaring riichi with a bad shape can be a possible solution.
You have two dora
Normally, the condition should be the same as that of dora 1. In a situation where the points are even, declaring riichi with a good shape is superior to declaring riichi with a bad shape.You have three dora
If riichi and damaten are both worth mangan, declaring riichi with a good shape is obviously better.
Riichi theory(7): Decision between tenpai with points difference - Part 1
I'll be separating the article into parts because it's really long. :(
Source: http://blog.jpmahjong.net/read.php/621.htm
We're basically at the end of the riichi theories, which is also the hardest part to understand.
Everyone should have had hands that can go into tenpai with different waits, and hands with a good shape that has a lower value than hands with a bad shape. For example:
This hand has three choices.
1. Good shape(Discard 7 sou) riichi
2. Bad shape(Discard 4 sou) damaten
3. Bad shape(Discard 4 sou) riichi
As mentioned before, you should declare riichi when you have a good shape, therefore there's no need to consider the first option.
The point of this article is to find out which is the correct method.
I'll first introduce an important theory.
The winning rate of riichi with a good shape is similar to that of damaten with a bad shape.
This theory is based on the huge amount of statistics by 凸本. If riichi and damaten has the same amount of points, it is more advantageous to declare riichi. This is due to ippatsu and ura-dora.
Hence
For this type of hand, discarding 1 wan and declaring riichi is better than discarding 4 wan and staying in damaten.
As for the example in the beginning, riichi with a good shape is 3900 points, while damaten with a bad shape is 5200 points. Similarly, riichi with a good shape is definitely better than damaten with a bad shape. A 3900 points ryanmen riichi has a winning average of 6000 points and above.
Then how does a good shape and a bad shape compare when declaring riichi?
For this kind of points, the good shape is more advantageous. The riichi with the bad shape is 4 han 30 fu, the effectiveness of ura-dora etc will be reduced. However, the winning rate will be a grade lower and the expected value is not comparable to that of the riichi with the good shape.
Hence, unless it's all last where you need tsumo haneman or other special situations, declaring riichi with a good shape is the correct answer. This sort of shape is worthwhile for everyone to take note.
Source: http://blog.jpmahjong.net/read.php/621.htm
We're basically at the end of the riichi theories, which is also the hardest part to understand.
Everyone should have had hands that can go into tenpai with different waits, and hands with a good shape that has a lower value than hands with a bad shape. For example:
This hand has three choices.
1. Good shape(Discard 7 sou) riichi
2. Bad shape(Discard 4 sou) damaten
3. Bad shape(Discard 4 sou) riichi
As mentioned before, you should declare riichi when you have a good shape, therefore there's no need to consider the first option.
The point of this article is to find out which is the correct method.
I'll first introduce an important theory.
The winning rate of riichi with a good shape is similar to that of damaten with a bad shape.
This theory is based on the huge amount of statistics by 凸本. If riichi and damaten has the same amount of points, it is more advantageous to declare riichi. This is due to ippatsu and ura-dora.
Hence
For this type of hand, discarding 1 wan and declaring riichi is better than discarding 4 wan and staying in damaten.
As for the example in the beginning, riichi with a good shape is 3900 points, while damaten with a bad shape is 5200 points. Similarly, riichi with a good shape is definitely better than damaten with a bad shape. A 3900 points ryanmen riichi has a winning average of 6000 points and above.
Then how does a good shape and a bad shape compare when declaring riichi?
For this kind of points, the good shape is more advantageous. The riichi with the bad shape is 4 han 30 fu, the effectiveness of ura-dora etc will be reduced. However, the winning rate will be a grade lower and the expected value is not comparable to that of the riichi with the good shape.
Hence, unless it's all last where you need tsumo haneman or other special situations, declaring riichi with a good shape is the correct answer. This sort of shape is worthwhile for everyone to take note.
Friday, 9 March 2012
Riichi theory(6): Tips to riichi
Source: http://blog.jpmahjong.net/read.php/620.htm
The previous articles introduced a few commonly seen examples of whether or not to declare riichi. Next, we'll discuss what tile you should declare riichi with.
It may seem like a trivial matter, but as the error piles up, it may adversely affect your results.
Choose the tenpai that lets you win easily
This can be considered a basic tenet of riichi, for example:
I believe that everyone would discard 4 sou and riichi.
Sometimes, a tile isn't necessarily easier to win on just because it's been discarded less. In the above example, even if a nan has been discarded and not a single 4 sou has been discarded, declaring riichi and waiting on nan is still the correct choice. A guest wind tile that has been discarded once is a very good wait.
What about this hand?
It's a no brainer to declare riichi here with dora 3. However, I'll only give you 90 marks if you declare 9 pin here. Personally, I would discard 2 wan here and wait on tanki 1 wan. Even though the number of tiles you can wait on is one lesser, there are two advantages in waiting for 1 wan.
1. 1 wan is more difficult to use compared to 3 wan, and it is much easier for it to be discarded. This effect is much more pronounced when the riichi is an early one and there are no safe tiles.
2. After discarding 2 wan, everyone will discard it as it's a genbutsu. 2 wan will gradually become kabe, thereby increasing the chances of someone discarding 1 wan.
The winning rate of 1 wan here should be higher than that of 3 wan.
Prioritize ankou of terminal tiles
Hands that do not have pinfu, should retain ankou of terminal tiles if possible. Like the following:
You should never discard 2 pin, but discard 3 pin here.
Terminal ankous are worth 8 fu, and the fu of the hand will be 40 fu if you get a tsumo. There's a difference between 1000 - 2000 points and 1300 - 2600 points.
Chance of ura-dora
Ura-dora is an important right of riichi, but a careless discard can affect your chances of getting ura-dora.
In normal situations, you would discard 5 wan and not 2 wan, and declare riichi. The hand is obviously aiming for ura-dora in order to reach mangan, and therefore should increase the chances of getting ura-dora.
However, there are exceptions to this.
The current round is all last and you're the dealer, the difference between you and the top player is 20000 points. Winning with a riichi tsumo mangan and getting a renchan in order to achieve gyakuten is a good idea, however, it would be perfect to get a tsumo haneman and achieve gyakuten in one shot.
Getting an ura-dora 1 would only mean an increase of 300 points, whereas ura-dora 2 gets you a haneman. Hence in order to increase the chances of getting ura-dora 2, it would be better to discard 8 wan here.
The next article will be about making decisions between han value and number of waits during riichi.
The previous articles introduced a few commonly seen examples of whether or not to declare riichi. Next, we'll discuss what tile you should declare riichi with.
It may seem like a trivial matter, but as the error piles up, it may adversely affect your results.
Choose the tenpai that lets you win easily
This can be considered a basic tenet of riichi, for example:
I believe that everyone would discard 4 sou and riichi.
Sometimes, a tile isn't necessarily easier to win on just because it's been discarded less. In the above example, even if a nan has been discarded and not a single 4 sou has been discarded, declaring riichi and waiting on nan is still the correct choice. A guest wind tile that has been discarded once is a very good wait.
What about this hand?
It's a no brainer to declare riichi here with dora 3. However, I'll only give you 90 marks if you declare 9 pin here. Personally, I would discard 2 wan here and wait on tanki 1 wan. Even though the number of tiles you can wait on is one lesser, there are two advantages in waiting for 1 wan.
1. 1 wan is more difficult to use compared to 3 wan, and it is much easier for it to be discarded. This effect is much more pronounced when the riichi is an early one and there are no safe tiles.
2. After discarding 2 wan, everyone will discard it as it's a genbutsu. 2 wan will gradually become kabe, thereby increasing the chances of someone discarding 1 wan.
The winning rate of 1 wan here should be higher than that of 3 wan.
Prioritize ankou of terminal tiles
Hands that do not have pinfu, should retain ankou of terminal tiles if possible. Like the following:
You should never discard 2 pin, but discard 3 pin here.
Terminal ankous are worth 8 fu, and the fu of the hand will be 40 fu if you get a tsumo. There's a difference between 1000 - 2000 points and 1300 - 2600 points.
Chance of ura-dora
Ura-dora is an important right of riichi, but a careless discard can affect your chances of getting ura-dora.
In normal situations, you would discard 5 wan and not 2 wan, and declare riichi. The hand is obviously aiming for ura-dora in order to reach mangan, and therefore should increase the chances of getting ura-dora.
However, there are exceptions to this.
The current round is all last and you're the dealer, the difference between you and the top player is 20000 points. Winning with a riichi tsumo mangan and getting a renchan in order to achieve gyakuten is a good idea, however, it would be perfect to get a tsumo haneman and achieve gyakuten in one shot.
Getting an ura-dora 1 would only mean an increase of 300 points, whereas ura-dora 2 gets you a haneman. Hence in order to increase the chances of getting ura-dora 2, it would be better to discard 8 wan here.
The next article will be about making decisions between han value and number of waits during riichi.
Wednesday, 7 March 2012
Riichi theory(5): Tenpai with yaku having a bad shape
Source: http://blog.jpmahjong.net/read.php/616.htm
This section will explaining the benchmark of tenpai with yaku having a bad shape. There is actually very little difference between this part and other situations with bad shape.
Instant riichi with a 2600, 5200 point hand(including riichi)
There is no problem with declaring riichi immediately with this hand at all.
However since you can win in damaten with this hand, there are cases where people stay in damaten. You can choose to stay in damaten, if you realize that the current situation is dangerous or there's a situation that warrants going into betaori for.
Damaten with a 5200 points hand
The majority of modern mahjong players would stay in damaten with a 5200 points hand that has a bad shape. The only exceptions are when the current round of discard is early or when it's obvious that someone is attacking. (If there's already a situation where three exposed melds are made.)
Riichi only increases the points to 8000, and getting ura-dora would be pointless as the effectiveness is diminished. However if it's still early, there's a good chance of getting tsumo, you can try gunning for a ura-dora 1 haneman.
Tenpai with a [really bad shape]
A really bad shape refers to waiting on tiles that no one will discard, like a dora in the middle of a suit. For example:
Or an even more extreme example:
In the first example, waiting for a 5 wan to turn it into a 3 sided wait is a negative way to play. Beginners tend to assume that no one will discard the dora 7 wan. They will continue to wait even if the current situation is impossible to change tiles with. This is an unwise play style. Since you understand that the dora is a tile that will not come out even if you are in damaten, then you should also know that the side effect of riichi that decreases your winning rate is also hugely reduced. It'll at least be a mangan if you declare riichi and tsumo the dora, and it'll be haneman if you get ura-dora 1. Why not just declare riichi?
The second example follows the same reasoning. No one would simply discard a dora in the middle of a suit. Personally, Iwould declare riichi and aim for a tsumo.
True, this type of hand would usually end in ryuukyoku.(This type of dora tanki tenpai has a winning rate of 20 to 30 percent) However, a haneman is guaranteed if tsumo is achieved, and a baiman is possible if there is an ura-dora. It doesn't matter if the winning rate is a little low, right?
The next time will be discussing commonly used techniques during riichi.
This section will explaining the benchmark of tenpai with yaku having a bad shape. There is actually very little difference between this part and other situations with bad shape.
Instant riichi with a 2600, 5200 point hand(including riichi)
There is no problem with declaring riichi immediately with this hand at all.
However since you can win in damaten with this hand, there are cases where people stay in damaten. You can choose to stay in damaten, if you realize that the current situation is dangerous or there's a situation that warrants going into betaori for.
Damaten with a 5200 points hand
The majority of modern mahjong players would stay in damaten with a 5200 points hand that has a bad shape. The only exceptions are when the current round of discard is early or when it's obvious that someone is attacking. (If there's already a situation where three exposed melds are made.)
Riichi only increases the points to 8000, and getting ura-dora would be pointless as the effectiveness is diminished. However if it's still early, there's a good chance of getting tsumo, you can try gunning for a ura-dora 1 haneman.
Tenpai with a [really bad shape]
A really bad shape refers to waiting on tiles that no one will discard, like a dora in the middle of a suit. For example:
Or an even more extreme example:
In the first example, waiting for a 5 wan to turn it into a 3 sided wait is a negative way to play. Beginners tend to assume that no one will discard the dora 7 wan. They will continue to wait even if the current situation is impossible to change tiles with. This is an unwise play style. Since you understand that the dora is a tile that will not come out even if you are in damaten, then you should also know that the side effect of riichi that decreases your winning rate is also hugely reduced. It'll at least be a mangan if you declare riichi and tsumo the dora, and it'll be haneman if you get ura-dora 1. Why not just declare riichi?
The second example follows the same reasoning. No one would simply discard a dora in the middle of a suit. Personally, Iwould declare riichi and aim for a tsumo.
True, this type of hand would usually end in ryuukyoku.(This type of dora tanki tenpai has a winning rate of 20 to 30 percent) However, a haneman is guaranteed if tsumo is achieved, and a baiman is possible if there is an ura-dora. It doesn't matter if the winning rate is a little low, right?
The next time will be discussing commonly used techniques during riichi.
Friday, 2 March 2012
Riichi theory(4): Tenpai with no yaku having a bad shape
Source: http://blog.jpmahjong.net/read.php/614.htm
Next, we'll be discussing about tenpai with no yaku having a bad shape. (And also hands that shouldn't be in damaten.)
The biggest difference between bad shapes and good shapes, is that the former will need to consider the amount of effective tiles that can turn it into a good shape. As there is very little chances of winning, if your hand value is low or the current situation is dangerous, you can choose to go into betaori.
Unless the current situation is really dangerous, there's no problem with declaring riichi with this hand.
Beginners like to wait for 4 man before declaring riichi. Everyone has to remember that the tile you want to draw right now is 2 man, not 4 man, while the chances of drawing 4 man is the same as 2 man. If you draw 5 wan first, and then draw 4 wan later, you'll be in furiten. You can see that it is not effective to wait for a ryanmen here.
There are also those who would only declare riichi if they draw 5 wan, which is also a loss. If you had declared riichi earlier, it would have the same effect as doing it after drawing 5 wan. It's very important to restrict the discards of your opponent. Not only that, while your hand is damaten, your opponent's 2 wan is able to pass and the number of tiles you can win on decreases by one.
If you tsumo 2 wan, 1300-2600 points should be a pretty good return.
Then what about this type of hand?
There are two tiles that you can draw to turn into ryanmen, but you should just declare riichi. After declaring riichi, you can win from any of the other player's discards. Even though the number of tiles that allow you to change into ryanmen has doubled, you need to draw it yourself to use it. By my standards, I will only wait for tiles to change into a better shape only if there are 4-5 types. If the current discard round is already in the middle rounds, this standard will be stricter.
Number of dora and riichi judgement
Normally, if your hand has more than 2 dora, you should just declare riichi regardless of the shape.
There are 4 types and 16 tiles that allows you to change to ryanmen when you have shanpon. Not only that, you'll also get pinfu. However when you have dora 2, there's nothing wrong with declaring riichi immediately.
If there are not many tiles that you can use to change to ryanmen when the dora is only 1, just declaring riichi is also a tesuji in modern mahjong. Getting a mangan with tsumo and 1 ura-dora is not a rare occurrence.
As for pinfu-nomi that doesn't have any dora, the return is too low, the risk of riichi is relatively larger. You can choose to remain in damaten in this situation, and going to betaori if a dangerous situation arises.
Tanki tenpai
A tanki tenpai that only lacks a jantou will be waiting for tiles to turn into a good shape in most situations, the reason is that the number of tiles that you can use is a lot.
If you have 2-3 dora, you can discard 1 wan and declare riichi. If you have no dora, discard 2/4 pin and go for a tanki wait in damaten. There are many tiles that can be used to change your wait... 2356 wan, 69 sou, 5689 pin can be used to change into a good shape. Not only that, tanki wait on a guest wind is also a good choice.
Deciding whether or not to be in tenpai
In some situations where you have a tenpai with bad shape, choosing not to be in tenpai and going for a good shape is another common method. The following is an example:
Discarding 36 wan is tenpai without any yaku. However, discarding 9 pin here is a what an advanced player would do. 3456 wan is a very good shape mentioned earlier with many effective tiles. This hand will be able to turn into a tanyao pinfu. Regardless of winning rate or value, it's far superior to a 1300 points riichi hand.
It's important to be able to decide whether or not to be in tenpai. Beginners should try to understand it properly.
The next section will be about tenpai with yaku having a bad shape.
Next, we'll be discussing about tenpai with no yaku having a bad shape. (And also hands that shouldn't be in damaten.)
The biggest difference between bad shapes and good shapes, is that the former will need to consider the amount of effective tiles that can turn it into a good shape. As there is very little chances of winning, if your hand value is low or the current situation is dangerous, you can choose to go into betaori.
Unless the current situation is really dangerous, there's no problem with declaring riichi with this hand.
Beginners like to wait for 4 man before declaring riichi. Everyone has to remember that the tile you want to draw right now is 2 man, not 4 man, while the chances of drawing 4 man is the same as 2 man. If you draw 5 wan first, and then draw 4 wan later, you'll be in furiten. You can see that it is not effective to wait for a ryanmen here.
There are also those who would only declare riichi if they draw 5 wan, which is also a loss. If you had declared riichi earlier, it would have the same effect as doing it after drawing 5 wan. It's very important to restrict the discards of your opponent. Not only that, while your hand is damaten, your opponent's 2 wan is able to pass and the number of tiles you can win on decreases by one.
If you tsumo 2 wan, 1300-2600 points should be a pretty good return.
Then what about this type of hand?
There are two tiles that you can draw to turn into ryanmen, but you should just declare riichi. After declaring riichi, you can win from any of the other player's discards. Even though the number of tiles that allow you to change into ryanmen has doubled, you need to draw it yourself to use it. By my standards, I will only wait for tiles to change into a better shape only if there are 4-5 types. If the current discard round is already in the middle rounds, this standard will be stricter.
Number of dora and riichi judgement
Normally, if your hand has more than 2 dora, you should just declare riichi regardless of the shape.
There are 4 types and 16 tiles that allows you to change to ryanmen when you have shanpon. Not only that, you'll also get pinfu. However when you have dora 2, there's nothing wrong with declaring riichi immediately.
If there are not many tiles that you can use to change to ryanmen when the dora is only 1, just declaring riichi is also a tesuji in modern mahjong. Getting a mangan with tsumo and 1 ura-dora is not a rare occurrence.
As for pinfu-nomi that doesn't have any dora, the return is too low, the risk of riichi is relatively larger. You can choose to remain in damaten in this situation, and going to betaori if a dangerous situation arises.
Tanki tenpai
A tanki tenpai that only lacks a jantou will be waiting for tiles to turn into a good shape in most situations, the reason is that the number of tiles that you can use is a lot.
If you have 2-3 dora, you can discard 1 wan and declare riichi. If you have no dora, discard 2/4 pin and go for a tanki wait in damaten. There are many tiles that can be used to change your wait... 2356 wan, 69 sou, 5689 pin can be used to change into a good shape. Not only that, tanki wait on a guest wind is also a good choice.
Deciding whether or not to be in tenpai
In some situations where you have a tenpai with bad shape, choosing not to be in tenpai and going for a good shape is another common method. The following is an example:
Discarding 36 wan is tenpai without any yaku. However, discarding 9 pin here is a what an advanced player would do. 3456 wan is a very good shape mentioned earlier with many effective tiles. This hand will be able to turn into a tanyao pinfu. Regardless of winning rate or value, it's far superior to a 1300 points riichi hand.
It's important to be able to decide whether or not to be in tenpai. Beginners should try to understand it properly.
The next section will be about tenpai with yaku having a bad shape.
Thursday, 23 February 2012
More on ryanmen tenpai with yasume and takame
Source: http://blog.jpmahjong.net/read.php/612.htm
A reader raised a question about the previous article, regarding yasume and takame.
For example, if the hand is:
The yasume of 6 wan is worth 2000 points, while the takame of 9 wan is 7700 points. I mentioned that you should immediately declare riichi with this type of hand, but he feels that damaten is more advantageous. The reasoning is shown in the hand below.
Similarly, it's hand with takame of 7700 points and yasume of 2000 points. 凸本 mentioned before that you can ignore 6 wan with this sort of hand. Then could you follow suit with the previous menchin hand? If you follow suit, would a damaten be more advantageous?
If you only win on the takame with this sort of pinfu hand, it becomes a tenpai with a bad shape. According to 凸本's statistics, the difference between the winning rate for damaten with a bad shape and riichi with a good shape is minimal. The problem is when you declare riichi, would the chances of winning on the yasume of 6 wan be higher than in damaten?
If you only calculate the rate of winning, the rate of winning for 6/9 wan is close no matter if it's damaten or riichi. However, riichi will increase the chances of tsumo and if tsumo depends on chance, the chances of 6/9 wan appearing is higher. Hence, riichi will increase the winning rate of 6 wan.
The value of the yasume after riichi is 3900 points without ura-dora. The chances of getting ura-dora is 30%, and the value is 7700 points with one ura-dora. Hence, the expected value is 5000 points. If it's the takame, it's a haneman with one ura-dora and 8000 points without ura-dora. The expected value is over 9000.
If you add the two together, the expected value of over 7000 points is similar to that of the damaten of 7700 points. But don't forget that this result has not factor in the following:
1. Riichi increases the chances of tsumo, increasing the expected value. During damaten, the difference in points after tsumo is only 300 points, but after riichi, but the increase will be larger.
2. The risk of drawing the yasume of 6 wan while in damaten.
3. The advantages that riichi bring: ippatsu and the ability to stop other players from reaching tenpai.
In summary, it's more advantageous to declare riichi. With exposed melds, you can choose to ignore the yasume.
You should only be in damaten for this sort of hand if there are very little or no more 6 wan left, or when mangan is enough.
A reader raised a question about the previous article, regarding yasume and takame.
For example, if the hand is:
The yasume of 6 wan is worth 2000 points, while the takame of 9 wan is 7700 points. I mentioned that you should immediately declare riichi with this type of hand, but he feels that damaten is more advantageous. The reasoning is shown in the hand below.
Similarly, it's hand with takame of 7700 points and yasume of 2000 points. 凸本 mentioned before that you can ignore 6 wan with this sort of hand. Then could you follow suit with the previous menchin hand? If you follow suit, would a damaten be more advantageous?
If you only win on the takame with this sort of pinfu hand, it becomes a tenpai with a bad shape. According to 凸本's statistics, the difference between the winning rate for damaten with a bad shape and riichi with a good shape is minimal. The problem is when you declare riichi, would the chances of winning on the yasume of 6 wan be higher than in damaten?
If you only calculate the rate of winning, the rate of winning for 6/9 wan is close no matter if it's damaten or riichi. However, riichi will increase the chances of tsumo and if tsumo depends on chance, the chances of 6/9 wan appearing is higher. Hence, riichi will increase the winning rate of 6 wan.
The value of the yasume after riichi is 3900 points without ura-dora. The chances of getting ura-dora is 30%, and the value is 7700 points with one ura-dora. Hence, the expected value is 5000 points. If it's the takame, it's a haneman with one ura-dora and 8000 points without ura-dora. The expected value is over 9000.
If you add the two together, the expected value of over 7000 points is similar to that of the damaten of 7700 points. But don't forget that this result has not factor in the following:
1. Riichi increases the chances of tsumo, increasing the expected value. During damaten, the difference in points after tsumo is only 300 points, but after riichi, but the increase will be larger.
2. The risk of drawing the yasume of 6 wan while in damaten.
3. The advantages that riichi bring: ippatsu and the ability to stop other players from reaching tenpai.
In summary, it's more advantageous to declare riichi. With exposed melds, you can choose to ignore the yasume.
You should only be in damaten for this sort of hand if there are very little or no more 6 wan left, or when mangan is enough.
Saturday, 18 February 2012
Riichi theory(3): Pre-emptive tenpai hand with good shape
Source: http://blog.jpmahjong.net/read.php/611.htm
For the next three articles, I'll be introducing some commonly seen hands that you should declare riichi with and some hands that you should be in damaten for. Today will be concentrating on hands with tenpai waiting on ryanmen or above. The reader must note that the discussion here is assuming that no other player is attacking. (riichi, in tenpai with multiple exposed melds) To decide whether or not to declare riichi while an opponent is attacking, you should use the offence and defence judgement that was previously mentioned as a baseline.
All ryanmen tenpai should declare riichi, except for some special situations.
This is the tesuji of modern mahjong.
Then what are the "special situations"?
1. Hands with value haneman and above
The most commonly seen ones are either menzen chinitsu or honitsu.
Hands with value haneman and above should be in damaten. The reason is that the 1 han from riichi has little effect here, even not having any value. Your winning rate goes down after declaring riichi, therefore there's no benefit here.
Then, what about mangan tenpai?
With a hand with 7700 points, riichi's effects are smaller than a 1 or 2 han hand. If everyone has the same points, you can be in damaten to quickly take the lead. But if it's still early, the chances of winning is huge. Or if someone declares riichi, instantly declaring riichi to gamble for a haneman is also a viable choice.
2. All last and not needing the extra points to reach first place
This shouldn't need any explanation. (smile)
Basically, these should be all of the special situations.
Then does it mean that all the other ryanmen tenpai should declare riichi? Theoretically, that's correct. In a game between advanced players, a pre-emptive riichi is very powerful. Beginner advanced players(especially those around Tenhou's higher level tables) do not dare to declare riichi, crippling their firepower. The following shows a few common examples:
Pinfu dora 1
Beginner advanced players like sanshoku too much, and many of them stay in damaten for a hand like this.
There are people who stay in damaten just to wait for 7 sou. This type of hand is definitely a bad hand.
It's true that this hand is at least 7700 points if you draw 7 sou, however the problem is that the chances of someone discarding 14 pin or drawing them yourself is much higher than drawing 7 sou. (The former has 8 tiles, while the latter has 4 tiles.) The result is that hands like this often end up with damaten 2000 points or tsumo 700-1300 points. This is a huge waste. A instant riichi might not let you change tiles if you draw 7 sou, but if someone discards 14 pin, then you'll at least get 3900 points. Not only that, there's also a one in three chance of getting ura-dora, thus increasing the points to 7700 points which is equivalent to damaten pinfu sanshoku. Immediately declaring riichi has a chance of getting mangan, which is not lower than drawing 7 sou and then staying in damaten. With the various benefits of riichi, it's more advantageous to just declare riichi.
What about this kind of hand?
A hand that is at least 2000 points and as high as 7700 points. Many people will stay in damaten but you should instantly declare riichi with this kind of hand.
After declaring riichi, even if the yasume appears, there's still a good chance of getting ura-dora and turning the hand into a mangan, and even having a chance of becoming haneman if the takame appears. Drawing the yasume while in damaten is the real tragedy here.
No matter if the takame is on the inside or the outside, you should immediately declare riichi with this kind of hand.
Applying the same logic, you should not wait for ittsu with the hand below but declare riichi immediately.
An instant riichi with pinfu dora 1 is the basic among the basics.
Pinfu-nomi/No yaku ryanmen wait
Then what about pinfu nomi or a no yaku ryanmen wait?
The mainstream theory in the old days prefer damaten. The reason is that it's unreasonable to spend 1000 points to reach 1300/2000 points. However in today's time, this theory is outdated. This two types of hand are immediately declared riichi with.
Using pinfu nomi as an example, riichi pinfu is only 2000 points on the surface. However, if you include ippatsu ura-dora etc, the average points of pinfu nomi is above 3000 points. Added to the fact that opponents cannot freely make discards, declaring riichi is advisable.
Also, when we're in ryanmen wait, we'll rarely consider changing tiles.
Even if you can have tanyao by drawing 36 wan, or dora by drawing 7 sou, you should instantly declare riichi with this kind of hand. Half of the time after tenpai, winning happens within 5 rounds of discards. Even if you have 12 effectives tile, you'll still need 7-8 rounds of discards to draw it. Therefore in many instances, you'll find that before you draw your effective tile, you would already be able to win. This directly affects your scoring ability.
Pinfu dora 2
I've seen people who advocate damaten with pinfu dora 2 in some forum.
An instant riichi with pinfu dora 2 is better. It's at least 7700 points with riichi, there's also a better chance of tsumo haneman. There's a huge difference compared to winning 3900 points with damaten.
The only acceptable example is the dealer nearing ryuukyoku with a 5800 points tenpai. When the number of round of discards left is not much, maximizing your chances of winning to achieve renchan is a logical method, even though the points is not much. However, immediately declaring riichi is not a bad choice either.
Is the current round of discard related?
The aforementioned riichi standard should not be affected by the current round of discard. You should just declare riichi with pinfu dora 1, regardless of whether it's the 1st round or the 15th round. It's true that your chances of winning is low when you're close to ryuukyoku. However, do not forget that the success rate of damaten is also limited. Riichi also has the ability to cause other players to go into betaori, earning you the noten bappu. This is also riichi's intangible advantage.
In summary, you don't need to consider the current round of discard or tiles changing with pre-emptive ryanmen. There's nothing wrong with an instant riichi.
The next time will be discussing examples of tenpai with bad shapes.
For the next three articles, I'll be introducing some commonly seen hands that you should declare riichi with and some hands that you should be in damaten for. Today will be concentrating on hands with tenpai waiting on ryanmen or above. The reader must note that the discussion here is assuming that no other player is attacking. (riichi, in tenpai with multiple exposed melds) To decide whether or not to declare riichi while an opponent is attacking, you should use the offence and defence judgement that was previously mentioned as a baseline.
All ryanmen tenpai should declare riichi, except for some special situations.
This is the tesuji of modern mahjong.
Then what are the "special situations"?
1. Hands with value haneman and above
The most commonly seen ones are either menzen chinitsu or honitsu.
Hands with value haneman and above should be in damaten. The reason is that the 1 han from riichi has little effect here, even not having any value. Your winning rate goes down after declaring riichi, therefore there's no benefit here.
Then, what about mangan tenpai?
With a hand with 7700 points, riichi's effects are smaller than a 1 or 2 han hand. If everyone has the same points, you can be in damaten to quickly take the lead. But if it's still early, the chances of winning is huge. Or if someone declares riichi, instantly declaring riichi to gamble for a haneman is also a viable choice.
2. All last and not needing the extra points to reach first place
This shouldn't need any explanation. (smile)
Basically, these should be all of the special situations.
Then does it mean that all the other ryanmen tenpai should declare riichi? Theoretically, that's correct. In a game between advanced players, a pre-emptive riichi is very powerful. Beginner advanced players(especially those around Tenhou's higher level tables) do not dare to declare riichi, crippling their firepower. The following shows a few common examples:
Pinfu dora 1
Beginner advanced players like sanshoku too much, and many of them stay in damaten for a hand like this.
There are people who stay in damaten just to wait for 7 sou. This type of hand is definitely a bad hand.
It's true that this hand is at least 7700 points if you draw 7 sou, however the problem is that the chances of someone discarding 14 pin or drawing them yourself is much higher than drawing 7 sou. (The former has 8 tiles, while the latter has 4 tiles.) The result is that hands like this often end up with damaten 2000 points or tsumo 700-1300 points. This is a huge waste. A instant riichi might not let you change tiles if you draw 7 sou, but if someone discards 14 pin, then you'll at least get 3900 points. Not only that, there's also a one in three chance of getting ura-dora, thus increasing the points to 7700 points which is equivalent to damaten pinfu sanshoku. Immediately declaring riichi has a chance of getting mangan, which is not lower than drawing 7 sou and then staying in damaten. With the various benefits of riichi, it's more advantageous to just declare riichi.
What about this kind of hand?
A hand that is at least 2000 points and as high as 7700 points. Many people will stay in damaten but you should instantly declare riichi with this kind of hand.
After declaring riichi, even if the yasume appears, there's still a good chance of getting ura-dora and turning the hand into a mangan, and even having a chance of becoming haneman if the takame appears. Drawing the yasume while in damaten is the real tragedy here.
No matter if the takame is on the inside or the outside, you should immediately declare riichi with this kind of hand.
Applying the same logic, you should not wait for ittsu with the hand below but declare riichi immediately.
An instant riichi with pinfu dora 1 is the basic among the basics.
Pinfu-nomi/No yaku ryanmen wait
Then what about pinfu nomi or a no yaku ryanmen wait?
The mainstream theory in the old days prefer damaten. The reason is that it's unreasonable to spend 1000 points to reach 1300/2000 points. However in today's time, this theory is outdated. This two types of hand are immediately declared riichi with.
Using pinfu nomi as an example, riichi pinfu is only 2000 points on the surface. However, if you include ippatsu ura-dora etc, the average points of pinfu nomi is above 3000 points. Added to the fact that opponents cannot freely make discards, declaring riichi is advisable.
Also, when we're in ryanmen wait, we'll rarely consider changing tiles.
Even if you can have tanyao by drawing 36 wan, or dora by drawing 7 sou, you should instantly declare riichi with this kind of hand. Half of the time after tenpai, winning happens within 5 rounds of discards. Even if you have 12 effectives tile, you'll still need 7-8 rounds of discards to draw it. Therefore in many instances, you'll find that before you draw your effective tile, you would already be able to win. This directly affects your scoring ability.
Pinfu dora 2
I've seen people who advocate damaten with pinfu dora 2 in some forum.
An instant riichi with pinfu dora 2 is better. It's at least 7700 points with riichi, there's also a better chance of tsumo haneman. There's a huge difference compared to winning 3900 points with damaten.
The only acceptable example is the dealer nearing ryuukyoku with a 5800 points tenpai. When the number of round of discards left is not much, maximizing your chances of winning to achieve renchan is a logical method, even though the points is not much. However, immediately declaring riichi is not a bad choice either.
Is the current round of discard related?
The aforementioned riichi standard should not be affected by the current round of discard. You should just declare riichi with pinfu dora 1, regardless of whether it's the 1st round or the 15th round. It's true that your chances of winning is low when you're close to ryuukyoku. However, do not forget that the success rate of damaten is also limited. Riichi also has the ability to cause other players to go into betaori, earning you the noten bappu. This is also riichi's intangible advantage.
In summary, you don't need to consider the current round of discard or tiles changing with pre-emptive ryanmen. There's nothing wrong with an instant riichi.
The next time will be discussing examples of tenpai with bad shapes.
Tuesday, 14 February 2012
Riichi theory(2): Side-effects of riichi
Source: http://blog.jpmahjong.net/read.php/610.htm
Previously we mentioned the various advantages of riichi. This time will be about the disadvantages and restrictions.
1. Decrease in winning rate
Yes, it's is a well known fact that the winning rate after declaring riichi is lower than damaten.
The rate of success of riichi over 60% in ordinary games, whereas it's around 45% in phoenix games. While damaten ryanmen waits have a 60-80% chance of winning, as long as not many discards have been made. Riichi's winning rate is around 60% of damaten.
However as the value of riichi hands are two to three times of the original value, in addition to having a high chance of tsumo, the expected value of riichi hands is much higher than damaten.
2. 1000 points expenditure
In most situations, the 1000 point fee of riichi is no big deal. However if everyone has a small deviation in points, you might want to take it into consideration.
3. After declaring riichi, all tiles must be discarded unless it's the winning tile or a tile that you can make ankan with
Riichi is a hand exposing declaration. After declaring riichi, you cannot change your tiles in order to change your wait or increase it's value.
Also, even if you draw a dangerous tile, you must discard it.
In superior level games, examples of dealing ins are often after declaring riichi.
In summary, the reason why riichi is a main attacking method in Japanese mahjong is because it's advantages far outweigh it's disadvantages.
Naturally, the advantages and disadvantages are affected by different hands and points situations. This is the basis of whether or not to declare riichi.
However, I can first tell everyone two very important points.
Next, the following articles will discuss these three areas:
1. Hands which you should declare riichi and hands which you should be in damaten for
2. Standards of riichi, tesuji etc
3. Summary of riichi judgement
To be continued.
Previously we mentioned the various advantages of riichi. This time will be about the disadvantages and restrictions.
1. Decrease in winning rate
Yes, it's is a well known fact that the winning rate after declaring riichi is lower than damaten.
The rate of success of riichi over 60% in ordinary games, whereas it's around 45% in phoenix games. While damaten ryanmen waits have a 60-80% chance of winning, as long as not many discards have been made. Riichi's winning rate is around 60% of damaten.
However as the value of riichi hands are two to three times of the original value, in addition to having a high chance of tsumo, the expected value of riichi hands is much higher than damaten.
2. 1000 points expenditure
In most situations, the 1000 point fee of riichi is no big deal. However if everyone has a small deviation in points, you might want to take it into consideration.
3. After declaring riichi, all tiles must be discarded unless it's the winning tile or a tile that you can make ankan with
Riichi is a hand exposing declaration. After declaring riichi, you cannot change your tiles in order to change your wait or increase it's value.
Also, even if you draw a dangerous tile, you must discard it.
In superior level games, examples of dealing ins are often after declaring riichi.
In summary, the reason why riichi is a main attacking method in Japanese mahjong is because it's advantages far outweigh it's disadvantages.
Naturally, the advantages and disadvantages are affected by different hands and points situations. This is the basis of whether or not to declare riichi.
However, I can first tell everyone two very important points.
1. In Japanese mahjong, situations where you need to be in damaten is very rare.
2. You lose more points by not declaring riichi when you should than declaring riichi when you shouldn't. Next, the following articles will discuss these three areas:
1. Hands which you should declare riichi and hands which you should be in damaten for
2. Standards of riichi, tesuji etc
3. Summary of riichi judgement
To be continued.
Riichi theory(1): What is riichi?
Source: http://blog.jpmahjong.net/read.php/606.htm
Riichi is one of the four types of yaku in Japanese mahjong and holds an important position. Starting from today, I will be explaining various judgements related to riichi.
(Discussions related to situation judgements is still work in progress, it's just that collecting examples takes time. They will be posted once they're finished.)
(Translater note: The author is talking about another series of articles related to situation judgements. I decided to translate riichi theory first.)
To understand how to judge riichi, first you need to understand what is riichi. I've mentioned it before previously in articles of a higher difficulty, but this time is for beginners and the theories will be explained in detail. Today will be about the advantages of riichi.
Advantage:
Beginners tend to misunderstand riichi. The most common problem with them is underrating the advantage of riichi. Therefore it's important to understand the benefits of riichi.
1) Increase your hand value
Many people underestimate the attacking power from riichi. People used to say: "Pinfu-nomi's 1 han is only worth 1000 points, while there's only 2000 points after riichi. There's only 2000 points, so you should damaten."
For now, we won't discuss whether pinfu-nomi should declare riichi, but whether or not riichi can increase your original hand's value by 1 time, and pinfu-nomi is not just 1300 points.
I believe everyone has seen these kind of tiles:
Riichi Ippatsu Tsumo Ura-dora 1
Riichi Ura-dora 3
Riichi Ippatsu Tsumo Pinfu Ura-dora 1/2
With riichi, it's not rare to see examples of worthless hands turning into mangan or haneman. Riichi on average will have 1/3 ura-dora, and winning hands with riichi have ippatsu 20% of the time. If you add these up, in fact riichi has a value of 1.5-1.6 han. According to statistics, winning hands with pinfu-nomi riichi has 3000 points and above on average. Riichi has the ability to increase the value of pinfu-nomi by 3 times or more.
In addition, riichi will increase your tsumo proportion. If your hand is 2600 points, and you win on another player's discard while in damaten, the difference between the player who dealt in and the other two players is 5200 and 2600 points respectively. However if you declare riichi, even if you tsumo and didn't have any ura-dora, the difference between you and the other players is 5000 to 6000 points. There's a huge difference.
2) Restrict your opponent's dicards
This is something that is often neglected by most beginners and even some intermediate players.
Once someone declares riichi, unless the others have good tiles, they will not attack recklessly due to Japanese mahjong's payout system. This way, the opponents have lesser chance of winning. On the other hand, once the opponents have lower chances of winning, the amount of chances that you can draw tiles increases, indirectly increasing the value of the winning hand.
This explains why players declare riichi with a suuankou tenpai, the main motive is to increase the chances of drawing tiles.
3) Makes certain tiles easier to wait on
This is a tactic that everyone knows.
Luring the opponent to discard the suji-pai of the riichi tile(especially 19 suji-pai), guest wind, no chance tiles etc, will achieve the desired result.
However I ask everyone not to abuse this tactic, and only use it when it's suitable.
As for riichi's disadvantages, they will be discussed after my new year vacation.
Riichi is one of the four types of yaku in Japanese mahjong and holds an important position. Starting from today, I will be explaining various judgements related to riichi.
(Discussions related to situation judgements is still work in progress, it's just that collecting examples takes time. They will be posted once they're finished.)
(Translater note: The author is talking about another series of articles related to situation judgements. I decided to translate riichi theory first.)
To understand how to judge riichi, first you need to understand what is riichi. I've mentioned it before previously in articles of a higher difficulty, but this time is for beginners and the theories will be explained in detail. Today will be about the advantages of riichi.
Advantage:
Beginners tend to misunderstand riichi. The most common problem with them is underrating the advantage of riichi. Therefore it's important to understand the benefits of riichi.
1) Increase your hand value
Many people underestimate the attacking power from riichi. People used to say: "Pinfu-nomi's 1 han is only worth 1000 points, while there's only 2000 points after riichi. There's only 2000 points, so you should damaten."
For now, we won't discuss whether pinfu-nomi should declare riichi, but whether or not riichi can increase your original hand's value by 1 time, and pinfu-nomi is not just 1300 points.
I believe everyone has seen these kind of tiles:
Riichi Ippatsu Tsumo Ura-dora 1
Riichi Ura-dora 3
Riichi Ippatsu Tsumo Pinfu Ura-dora 1/2
With riichi, it's not rare to see examples of worthless hands turning into mangan or haneman. Riichi on average will have 1/3 ura-dora, and winning hands with riichi have ippatsu 20% of the time. If you add these up, in fact riichi has a value of 1.5-1.6 han. According to statistics, winning hands with pinfu-nomi riichi has 3000 points and above on average. Riichi has the ability to increase the value of pinfu-nomi by 3 times or more.
In addition, riichi will increase your tsumo proportion. If your hand is 2600 points, and you win on another player's discard while in damaten, the difference between the player who dealt in and the other two players is 5200 and 2600 points respectively. However if you declare riichi, even if you tsumo and didn't have any ura-dora, the difference between you and the other players is 5000 to 6000 points. There's a huge difference.
2) Restrict your opponent's dicards
This is something that is often neglected by most beginners and even some intermediate players.
Once someone declares riichi, unless the others have good tiles, they will not attack recklessly due to Japanese mahjong's payout system. This way, the opponents have lesser chance of winning. On the other hand, once the opponents have lower chances of winning, the amount of chances that you can draw tiles increases, indirectly increasing the value of the winning hand.
This explains why players declare riichi with a suuankou tenpai, the main motive is to increase the chances of drawing tiles.
3) Makes certain tiles easier to wait on
This is a tactic that everyone knows.
Luring the opponent to discard the suji-pai of the riichi tile(especially 19 suji-pai), guest wind, no chance tiles etc, will achieve the desired result.
However I ask everyone not to abuse this tactic, and only use it when it's suitable.
As for riichi's disadvantages, they will be discussed after my new year vacation.
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