Time control
A time control is a mechanism in the tournament play of almost all two-player board games so that each round of the match can finish in a timely way and the tournament can proceed. Time controls are typically enforced by means of a game clock, where the times below are given per player. Time pressure is the situation of having very little time on a player's clock to complete their remaining moves.
Classification
The amount of time given to each player to complete their moves will vary from game to game.However, most games tend to change the classification of tournaments according to the length of
time given to the players.
In chess, the categories of short time limits are: "bullet", "blitz", and "rapid".
"Bullet" games are the fastest, with either a very short time limit per move or a very short total time.
"Blitz" games typically give five to ten minutes per player, and "rapid" games give between ten and sixty minutes.
By way of contrast, for Go, anything under twenty minutes could be considered "blitz".
Methodology
The exact approach to using a game clock to regulate games varies considerably.Sudden death
This is the simplest methodology. Each player is assigned a fixed amount of time for the whole game. If a player's main time expires, they generally lose the game.Overtime formats
Here the game time is separated into two basic domains: the main time and the overtime. To switch between the two requires some trigger event, often the expiration of the main time. In chess, reaching a fixed number of moves can trigger the gain of a fixed amount of extra time. This usually occurs in long games after the 40th move: e.g. 120 minutes to complete the first 40 moves, and another 30 minutes to complete the rest of the game.In go two common forms are:
Byo-yomi
This timing method is also used in shogi. The word is borrowed from Japanese; the term literally means "counting the seconds", or more generally, "countdown".After the main time is depleted, a player has a certain number of periods. If a move is completed before the time expires, the time period resets and restarts the next turn. If a move is not completed within a time period, the time period will expire, and the next time period begins. This is written as
A typical time control is "60 minutes + 30 seconds byo-yomi", which means that each player may make as many or as few moves as he chooses during his first 60 minutes of thinking time, but after the hour is exhausted, he must make each move in thirty seconds or less. To enforce byo-yomi, a third person or a game clock with a byo-yomi option is necessary.
In professional Go games and many amateur tournaments, a player has several byo-yomi periods, for example five periods of one minute each. If a player makes his move within a one-minute period, he retains all five periods for his future moves. If a player oversteps one minute, he starts the following move in the second rather than the first byo-yomi period. In effect, the player has one minute per move plus four extra one-minute packets which may be used as needed, e.g. four moves of two minutes each, or one move of five minutes, or any other combination.
In higher-level tournaments, such as the Kisei tournament, the player's time is often composed entirely of byo-yomi periods, rather than having a main block of thinking time. In this case, the actual counting of time begins once the player falls below a certain threshold of time, such as 10 minutes; when the time is being counted, the player is informed at intervals how much time they have used in their current period, and how many extra periods they have left. Similarly, in the televised NHK Cup tournament, the player has 30 seconds per move plus 10 extra one-minute periods which may be used as needed.
When analog game clocks are used to enforce byo-yomi, it is more convenient to assign additional time for a block of moves, rather than for each move. In Canadian byo-yomi, a player typically gets 5 minutes for 10 to 20 moves. The IGS Go server uses a similar system, but the byo-yomi time is variable and always covers 25 moves. Thus the time control "20 minutes + 15 minutes byoyomi" on IGS means that after the initial 20 minutes of thinking time are over, a player is granted 15 additional minutes, which may be spent however he chooses. If these minutes expire before he has made 25 more moves, he loses. If he makes 25 more moves in less than 15 minutes, he is granted another 15 minutes of byo-yomi, and so on indefinitely.
Canadian byo-yomi imposes a certain average speed of play, but allows the player to spend more time to ponder on difficult moves. Several byo-yomi periods in one move per period variant serve essentially the same purpose, albeit to a lesser extent.
Unused time during one byo-yomi period does not carry forward to future moves. This is in contrast to the Fischer clock often used in chess, with designations such as "5 minutes + 12 seconds per move". Under this time control each player has twelve seconds added to his clock after every move, starting from the first move, regardless of how much time he spends on each move. Thus if a player thinks for eight seconds before making his first move, he will have five minutes and four seconds on his clock after making it.
Canadian overtime
After using all of their main time, a player must make a certain number of moves within a certain period of time — for example, twenty moves within five minutes. In Go, players stop the clock, and the player in overtime counts out the required number of stones and sets the remaining stones out of reach so as not to become confused, whilst the opponent sets the clock to the overtime period. If all the moves are made in time, then another period of overtime starts — another set of stones and the timer again reset to the overtime period. If all the moves are not made in time, the player has lost on time. This is written asIncrement and delay methods
These are the timing methods most often used in chess.Increment —a specified amount of time is added to the players main time each move, unless the player's main time ran out before they completed their move. For example, if the time control is G/90;inc30, each player gets an additional thirty seconds added to their main time for each move, unless the player's main time ran out first. Under FIDE and US Chess rules you get the increment for move one as well. For example, for G/3;inc2 you start with three minutes and two seconds on the first move. Not all digital chess clocks automatically give the increment for move one and thus for those that don't, the increment time has to be added manually to the main time so each player gets the increment for move one.
Bronstein delay —this timing method adds time but unlike increment not always the maximum amount of time is added. If a player expends more than the specified delay, then the entire delay is added to the player's clock but if a player moves faster than the delay, only the exact amount of time expended by the player is added. For example, if the delay is ten seconds and a player uses ten or more seconds for a move, ten seconds is added after they complete their move. If the player uses five seconds for a move, five seconds is added after they complete their move. This ensures that the main time left on the clock can never increase even if a player makes fast moves. As with increment, you get the delay time to move one under FIDE and US Chess rules.
Simple delay —with this timing method, the clock waits for the delay period each move before the player's main time starts countdown down. For example, if the delay is ten seconds, the clock waits for ten seconds each move before the main time starts counting down.
Bronstein delay and Simple delay are mathematically equivalent. The advantage of Bronstein delay is that you can always quickly see exactly how much time you have for your next move without having to add the main and delay time together in your head. The advantage of Simple delay is that you can always tell if the time that is counting down is the delay time or the main time. Simple delay is the form of delay most often used in the US while Bronstein delay is the form of delay most often used in most other countries.