This is a purely hypothetical question, as I have no particular intention of ever running this kind of event, but as I was examining clock controls, it made me curious.
The Saitek Competition Pro, Chronos II and DGT 2010 all include “Bronstein” time: a kind of added time in which seconds are added to your timer at the end of your move (as with increment time) but you cannot get back more time than you’ve used for your move (as with delay). If one were to use Bronstein time in a rated tournament, would the time control be given as delay or increment – or is there no accommodation of Bronstein time within USCF rules, and would the tournament not even be ratable? And if the last is true, then how did it wind up as a feature on so many clocks?
Someone will soon point out that a time control of T with delay D is mathematically equivalent to a time control of T+D with Bronstein delay D. Hey, I guess that person was me.
That is, for a given session of two players playing a chess game and hitting the clock in alternation at various times, the same person will run out of time at the same time no matter which of the above two settings the clock is set to.
Someone else will soon claim even though the two cases are mathematically equivalent, they’re still not really the same thing, which is the point at which I stop paying attention to the conversation.
DGT 2010 supports Bronstein but not delay. DGT NA supports delay but not Bronstein. A big reason that clock was developed, I think.
Excalibur Game Time II and Saitek Competiton Scholatic blue do delay but not Bronstein. The old-style long Chronos supports both; I think the newer, shorter model does, too, but not sure about that.
Bronstein is treated as equivalent to delay. Look at the TD Tip on page 10 of the 5th Edition, under Rule 5F: “Delay mode and Bronstein mode are equivalent.”
There is some debate—including on this forum, some of it recent—as to whether the two modes are ‘precisely’ equivalent. (Assuming you add the time before the first move in Bronstein mode.) The question is whether a player with less than 5 seconds left in SD gets as much thinking time in Bronstein as he does in straight delay.
In practice, straight delay is so much more common that some organizers/TDs announce and post that delay is preferred to Bronstein at their events. I saw a sign that stated that once, I think at the Marshall Chess Club. Some players do not like any mode that does not show the delay time tick down before the main time kicks in, too.
I used Bronstein (adagio) mode once, on my Chronos at the 2012 USATE. I expected my opponent to complain or at least ask about it, but he never said a word. Bronstein can be considered more elegant than straight delay, maybe, but the ship has sailed for mainstream USCF events.
The players gets exactly the same thinking time in the two modes. The only difference is in how the time is displayed. On any given move, your time can be viewed as consisting of the sum of two components: your “main thinking time” (FIDE terminology) and your delay time. Delay clocks show your main thinking time. Bronstein clocks show the sum of main thinking time and delay time.
Let’s take a precise look at how the two modes handle an arbitrary move. We’ll need some terminology and definitions:
M_in = the main thinking time at the start of your move
M_out = the main thinking time at the completion of your move
D = the delay
T = the total time you spend on the move
C(t) = what the clock shows
For example, for a G/30 d5 game, at the start for each player M_in=1800 seconds, D=5.
Here is how a delay clock works.
(1) When t <= D, C(t) = M_in
(2) When t > D, C(t) = M_in - (t-D)
(3) M_out = C(T)
(4) Flag falls when C(t)=0, which happens when t = M_in + D.
In English, the delay clock shows your main thinking time.
Here is how a Bronstein clock works:
(5) C(t) = M_in + D - t
(6) If T <= D, M_out = C(T) + T - D = M_in + D - T + T - D = M_in
(7) If T > D, M_out = C(T) + D - D = C(T) = M_in + D - T = M_in - (T-D)
(8) Flag falls when C(t) = 0, which happens when t = M_in + D.
In English, the Bronstein clock shows the time remaining to make your move.
Let’s consider a move where we have M_in main thinking time at the start of the move, and we take T seconds, where T <= D.
On the delay clock, M_out = C(T) (rule 3), and since T <= D, C(T) = M_in (rule 1). So, on the delay clock, M_out = M_in, just as it should be (since we got our move in during the delay).
On the Bronstein clock, M_out = M_in (rule 6), which is the same as for the delay clock.
Now let’s consider a move where we exceed the delay, so T > D.
On the delay clock, M_out = C(T) (rule 3). C(T) = M_in - (T-D) (rule 2). So, M_out = M_in - (T-D). This is what we expect–the amount we exceeded the delay comes off our main thinking time.
On the Bronstein clock, M_out = M_in - (T-D) (rule 7), which is the same as for the delay clock.
Finally, let’s consider when the flag falls if we fail to move. As can be seen from rules 4 and 8, this happens at the same time on the delay clock and the Bronstein clock.
Note that the above applies no matter what the main thinking time is. There is nothing special about main thinking times that are less than D.
Conclusion: the two modes account for thinking time precisely the same.
Some examples might make this clearer. Let’s say you have 120 seconds main thinking time left, and you take 17 seconds to move. Assume 5 second delay.
On the delay clock, the display says 120 at the start of your move, and continues to say 120 for the first 5 seconds of your 17 second move, and then begins counting down, reaching 108 by the time your make your move after 17 seconds have elapsed. The clock stops at 108, showing you that you have 108 second of main thinking time left.
On the Bronstein clock, the display says 125 at the start of your move, and begins counting down immediately. When you complete the move, after 17 seconds, the clock is down to 108. When you hit the clock, the display jumps to 113, to show you that you have 113 seconds for your next move (108 seconds of main thinking time, and the 5 second delay).
Later, you are down to 3 second main thinking time when your move starts. We’ll suppose you make your move in 4 seconds.
The delay clock shows 3 seconds on the display. You complete the move before 5 seconds pass, so the display does not change. You end the move with the clock still saying 3 seconds.
On the Bronstein clock, the clock shows 8 seconds at the start of your move. That counts down to 4 while you move, and then when you hit the clock, 4 seconds are added back (not 5, because you moved in less than the delay time, so you get your move time back, not the full delay back), so the clock ends up at 8 seconds, which is where it started, representing 3 seconds of main thinking time, and 5 seconds of delay time).
Next move, you take 7 seconds.
On the delay clock, the clock starts counting down after 5 seconds, so you lose 2 seconds on the display, leaving the clock at 1 second, representing the 1 second of main time you have for your next move.
On the Bronstein clock, the clock starts counting down immediately from 8. You hit the clock 7 seconds later, when it says 1 second. Since you took the full delay time, you get 5 seconds back, rather than your move time, so the clock jumps to 6 seconds, representing 1 second of main thinking time, and 5 seconds of delay.
Good show, TZS. For a similar explanation of the mathematical equivalence of Bronstein and delay, see this post.
As for thepsychologicaladvantages and disadvantages of each, that swings both ways, and also may depend on the clock brand.
Assuming that, in delay mode, the clock is capable of displaying both delay time and main time simultaneously (as actual digits, not just as hyphens or flashing colons), the arguments could run as follows:
X: “I prefer straight delay over Bronstein. That way, with a 5-second delay, I can optimize my use of time by using 4.9 seconds on each move. My main time never shrinks.”
Y: “OK, but I find the dual display confusing. In Bronstein mode, only one time quantity is showing, and it’s the exact amount of time remaining before my flag falls.”
X: “Sure, but try optimizing your use of time as above. You’d have to mentally record the clock time at the start of your move, and make your move exactly 4.9 seconds later. By the time I’ve made the necessary mental calculation, my entire 5 seconds might already be used up!”
Y: “As would mine, if I have to look at two time displays at the same time and figure it out. Give me a single display!”
Add to this debate the variety of ways different clocks display delay, and things get still murkier. X would hate the DGT North American, which simply displays the word “Delay” for five seconds, while the main time remains visible. Y would hate the Saitek, which shuts off the main time display entirely during the delay. Both X and Y might prefer Bronstein mode over either of these “defective” delay modes.
How many clocks display both the delay time and the main time simultaneously, as digits? As far as I know, only the Excalibur, and some modes on the Chronos.
Meanwhile, Keith, forget about running a Bronstein tournament. That would be the same as a delay tournament; you might as well call it by its familiar name.
Kind of, but this erroneously presumes that a player will ever have 5 or fewer seconds left in Bronstein mode. In Bronstein, one can’t have a start-of-move display time of less than six seconds, because in order to get to a shorter start-of-move time, one has to flag first.
This is the reason for the psychological inequivalence of the mathematically equivalent delay and Bronstein modes.