D’Alembert is a progressive betting system helping get losses back in small portions unlike the Martingale where you get back all at once. Created for use while playing roulette on the even chance bets the system can be used in any game with even chance bet.
This system is based on the idea that in the long run the player and the banker will have an equal number of wins. If a player begins by betting one unit ($1, $3 or any other sum) on the player, and loses he should increase the following bet by one unit and if he wins he should decrease the following bet by the same one unit. Suppose, the player bet on the player and got the following results:
|1 (-1)||2 (-3)||3 (-6)||4 (-2)||3 (-5)||4 (-1)||3 (+2)||2 (+0)||3 (+3)||2 (+5)||1 (+6)|
(the numbers in brackets reflect the your bankroll after each round)
This sequence will result in a win of $6. If the number of wins is similar to the number of losses and one, such sequence causes a win. Also after rounds 7, 9 and 10 the player gets a profit, as the bets put on winning rounds are one unit bigger than the prior losing round. The positive likelihood before the sequence is over allows the gambler to make the session shorter after a moderate win and not to risk further that may result in bad ending.
Though D’Alembert reduces the possibility of losing your bankroll the opportunity of this remains there. A long sequence of constant losses or if the banker wins oftener than the player makes the system very disadvantageous and makes it impossible for the player to recover. Since the casino edge always works on every round, when you increase your bets you can increase your losses in the end.