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Bayesian Programming and Learning for Multi-Player Video Games ...

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at the dynamics or army compositions (section 7.7). For tactics (see chapter 6), we learned<br />

the co-occurrences of attacks with regions tactical properties.<br />

Finally, we produced a StarCraft bot (chapter 8), which ranked 9th (on 13) <strong>and</strong> 4th (on 10),<br />

respectively at the AIIDE 2011 <strong>and</strong> CIG 2011 competitions. It is about 8th (on ≈ 20) on an<br />

independent ladder containing all bots submitted to competitions (see Fig. B.8).<br />

9.2 Perspectives<br />

We will now present interesting perspectives <strong>and</strong> future work by following our hierarchical decomposition<br />

of the domain. Note that there are bridges between the levels presented here. In<br />

particular, having multi-scale reasoning seems necessary to produce the best strategies. For<br />

instance, no current AI is able to work out a “fast exp<strong>and</strong>*” (exp<strong>and</strong> be<strong>for</strong>e any military production)<br />

strategy by itself, in which it protects against early rushes by a smart positioning of<br />

buildings, <strong>and</strong> it per<strong>for</strong>ms temporal reasoning about when the opponent is first a threat. This<br />

kind of reasoning encompasses micro-management level reasoning (about the opponent units),<br />

with tactical reasoning (of where <strong>and</strong> when), buildings positioning, <strong>and</strong> economical <strong>and</strong> production<br />

planning.<br />

9.2.1 Micro-management<br />

Reactive behaviors<br />

An improvement (explained in subsection 5.6.1) over our existing model usage would consist<br />

in using the distributions on directions (P(Dir)) <strong>for</strong> each units to make a centralized decision<br />

about which units should go where. This would allow <strong>for</strong> coordinated movements while retaining<br />

the tractability of a decentralized model: the cost <strong>for</strong> units to compute their distributions on<br />

directions (P(Dir)) is the same as in the current model, <strong>and</strong> there are methods to select the<br />

movements <strong>for</strong> each unit which are linear in the number of units (<strong>for</strong> instance maximizing the<br />

probability <strong>for</strong> the group, i.e. <strong>for</strong> the sum of the movements).<br />

For the problem of avoiding local optima “trapping”, we proposed a “trailing pheromones<br />

repulsion” approach in subsection 5.6.1 (see Fig. 5.14), but other (adaptive) pathfinding approaches<br />

can be considered.<br />

Parameters identifications<br />

Furthermore, the identification of the probability distributions of the sensors knowing the directions<br />

(P(Sensor|Direction)) is the main point of possible improvements. In the industry,<br />

behavior could be authored by game designers equipped with an appropriate interface (with<br />

“sliders”) to the model’s parameters. As a competitive approach, rein<strong>for</strong>cement leaning or evolutionary<br />

learning of the probability tables (or probability distributions’ parameters) seems the<br />

best choice. The two main problems are:<br />

• types <strong>and</strong>/or levels of opponents: as we cannot assume optimal play from the opponents<br />

(at least not <strong>for</strong> large scale battles), the styles <strong>and</strong> types of the opponents’ control will<br />

matter <strong>for</strong> the learning.<br />

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