Cumulative addback and non-cumulative addback – how do today’s chess clocks implement each of these?
For games played with non-cumulative addback, two implementations are available:
- In Bronstein mode, the addback time (typically 5 seconds) or the time actually used, whichever is less, is added back to the player’s main time each time he presses the clock.
- In straight delay mode, the clock simply waits for the addback time to expire, before the main time starts to run, each time the player presses the clock.
Some clocks (e.g. DGT) offer Bronstein mode. Others (e.g. Excalibur) offer straight delay. At least one (Chronos) offers both.
The best way to implement straight delay mode, IMHO, is via a separate countdown digit, counting from the addback time (e.g. 5 seconds) down to zero at the beginning of each move. Less desirably, a flashing colon or flashing hyphen is sometimes used for this purpose.
Bronstein and straight delay are mathematically equivalent, as demonstrated in this post. There are, however, important psychological differences for some players. Preferences vary, but some USA organizers have been known to give the nod to straight delay over Bronstein.
Now, what implementations are available for cumulative addback? At present there is only one:
- In increment mode, the addback time (typically 30 seconds) is added back to the player’s main time each time he presses the clock.
Which version of non-cumulative addback (Bronstein or straight delay) most closely resembles cumulative addback (increment)? The answer, of course, is Bronstein. In fact, the only difference between increment and Bronstein (as described above) is the omission or inclusion of the phrase “or the time actually used, whichever is less”.
Would anybody like to see an alternative implementation of cumulative addback, that resembles straight delay more than it does Bronstein? Let’s call it “visible cumulative” mode:
- In visible cumulative mode, as in straight delay mode, the clock would simply wait for the addback time to expire before the main time starts to run. But if the player uses less than his full addback time (e.g. less than 30 seconds), then the difference would be added back to the player’s main time when he presses his clock.
As with straight delay, the best way to display the addback time would be with a separate countdown digit, counting from (for example) 30 seconds down to zero.
Here is an example using a 30-second increment in the proposed “visible cumulative” mode. Let’s say the clock display is as follows just after black completes his 5th move and starts white’s clock:
white: 1:28:07 - 30
black: 1:23:48 - 30
The 30-second indicator on white’s clock immediately starts counting down toward 0. After it reaches 0, white’s main time immediately begins counting down from 1:28:07 toward 0:00:00.
But, if white uses only 19 seconds, then his remaining 11 seconds is added back to his main time. When white presses his clock, the display now shows:
white: 1:28:18 - 30
black: 1:23:48 - 30
– and black’s 30 seconds begins counting down toward 0. White’s addback time is reset to 30 seconds, and stays there until black moves and presses his clock.
Does anybody besides me see a possible benefit to this proposed “visible cumulative” implementation of increment?
Bill Smythe