A common paradigm in classical planning is heuristic forward search. Forward
search planners often rely on simple best-first search which remains fixed
throughout the search process. In this paper, we introduce a novel search
framework capable of alternating between several forward search approaches
while solving a particular planning problem. Selection of the approach is
performed using a trainable stochastic policy, mapping the state of the search
to a probability distribution over the approaches. This enables using policy
gradient to learn search strategies tailored to a specific distributions of
planning problems and a selected performance metric, e.g. the IPC score. We
instantiate the framework by constructing a policy space consisting of five
search approaches and a two-dimensional representation of the planner's state.
Then, we train the system on randomly generated problems from five IPC domains
using three different performance metrics. Our experimental results show that
the learner is able to discover domain-specific search strategies, improving
the planner's performance relative to the baselines of plain best-first search
and a uniform policy.

引入一种新的搜索框架来解决规划问题，该框架能够在解决特定规划问题时在几种前向搜索方法之间交替使用，使用可训练的随机策略来选择搜索方法，进而优化搜索策略，实验结果表明该框架优于传统的最佳优先搜索和均匀策略方法。