overview

duckmind is a collection of projects that are based on Sor's AI engine, and provides its game-playing AI functionality as a reusable library.

It implements the multi-phase AI system described in duck intelligence.

Generally, this system is based around the idea of hierarchically combining multiple advanced game-playing AI algorithms into a decision making and action pipeline.

features

the Ducia library provides the core AI algorithms and classes. when using them in external projects, they are typically subclassed for application specific functionality, though many good defaults are provided.

  • Framework - Core AI algorithms, including pathfinding, goal-oriented action planning, and utility-based reasoners

  • Calc - mathematical utility classes for AI-related computations

  • Cogs - personality engine classes (dating back to lunchlib)

  • Layers - abstract framework for combining multiple Systems in a sense-think-act architecture

concepts

mind

the Mind is the encapsulating representation of the AI consciousness of an agent. it represents a unit that implements the sense-think-act architecture.

the sense-think-act paradigm can be summarized as follows: + sense: receive input from the environment and convert it to a useful representation + think: based on environment state, make plans and decisions to respond to the environment + act: given a set of plans, carry them out in a coordinated manner

state

every agent will have a single mind, and this mind has an associated MindState, which serves as the working memory and cache.

systems

the mind is itself composed of various systems, which are reusable units of functionality that can be instanced across multiple minds.

systems are divided into sensory and cognitive systems: + sensory systems run during the sense phase, and serve to gather information about the environment and store it in working memory for quick access + cognitive systems run during the think phase, and run the planning algorithms to make decisions and plans based on available information

example systems: Sor
  • the Vision system is a basic sensory system that detects nearby birds and stores the results in working memory.

  • the Think system is a PlannerSystem, which is a type of cognitive system that uses a utility reasoner to make decisions.

pipelines

the mind has two main pipelines: the autonomous pipeline and the conscious pipeline.

autonomous pipeline

generally, the autonomous pipeline runs on the main thread, because it is designed to run quickly and not require complex computation. in addition, it frequently needs to access game state, so by running on the game thread, up-to-date game state information is readily available.

conscious pipeline

generally, the conscious pipeline is offloaded to the thread pool, and runs asynchronously independently of the autonomous pipeline. the conscious pipeline includes the think phase, which includes complex AI algorithms that can require a significant amount of time to execute. thread-pooling the AI makes efficient use of modern multi-core CPUs to maximize information throughput when simulating many agents.

thread-pooling is enabled by default, but can be disabled by setting Mind.useThreadPool to false. when thread-pooling is disabled, the conscious pipeline will be run between the sense and act phases on the autonomous pipeline's thread, usually the main thread.

since working memory is cached in the MindState, this pipeline can generally work completely independently of the autonomous pipeline. when results are ready, it can use message queues in the MindState to pass information to the act phase.

signals

signals represent events in a way roughly analagous to nervous system impulses. signals are sent to a mind by the external environment, passing an important message about the environmental interaction.

within the conscious pipeline, during the think phase, systems based on PlannerSystem are able to process signals.

in the context of a game, certain events such as being hit by an object within the game physics engine should call Mind.signal to add a signal to the signal queue in working memory.

plan

the Plan is the secondary layer in the hierarchical planning pipeline.

the purpose of the Plan layer: given a general goal, search the available action space and put together a plan to achieve the goal.

put simply: plan a sequence of actions to satisfy a goal

this is generally implemented via goal-oriented action planning. in Ducia, this is done using the ActionPlanningModel class, which is based on Activ BeyondGOAP.

a model is simply a set of variables that indicates an intermediate step in the plan.

for example, in a model for gathering flowers, a flowersGathered value would track the number of flowers gathered so far.

goals are specified as predicates: flowersGathered > 4= indicates a goal meaning that actions have been taken to increase the number of flowers over this threshold.

options, costs, and conditions

each action has an associated cost to execute. an action and its cost together are known as an option.

each action also specifies preconditions and postconditions: + preconditions indicate the requirements for an option to be valid + postconditions, a.k.a. effects, indicate the effect of taking an action on the planning model

by specifying our constraints in preconditions, we ensure that all sequences created of these actions are valid.

planning

selecting an optimal plan given a set of options is fairly straightforward. typically it is done using a graph-search algorithm such as A* to find the path to the goal with the least cost.

the solver is called by using Solver<T>.Next(model, goal) given a model instance

if no valid combination of the options leads to the goal, the solver returns null.