Discounted and Rapid Subfair Red-and-Black

Abstract

A gambler seeks to maximize the expected utility earned upon reaching a goal in a game where he is allowed at each stage to stake any amount of his current fortune. He wins each bet with probability $w$. In the discounted case the utility at the goal is $\beta^n$ where $\beta$, the discount factor, is in $(0, 1)$ and $n$ is the number of plays used to reach the goal. In the rapid case the utility at the goal is 1 and the gambler seeks to minimize his expected playing time given he reaches the goal. Here all optimal strategies are characterized when $w \leqq \frac{1}{2}$ for the discounted case and when $w < \frac{1}{2}$ for the rapid case. It is shown that when $w < \frac{1}{2}$ the set of rapidly optimal strategies coincides with the set of optimal strategies for the discounted case.