Fluent NHibernate: Model Markov chain
I want to use Fluent NHibernate to model a Markov chain. It's basically a set of different states with transition probabilities between the states.
I want to map the transition probabilities into MarkovState.TransitionProbabilities as a Dictionary. I want to use the NEXT state as key (using either MarkovState or int as key), so that I can do lookups like:
float probability = currentState.TransitionProbabilities[nextState.Id].Probability;
My database model:
CREATE TABLE MarkovState
(
Id int IDENTITY(1,1) NOT NULL,
StateContent varchar(10) NOT NULL
);
CREATE TABLE TransitionProbability
(
Id int IDENTITY(1,1) NOT NULL,
CurrentState_Id int NOT NULL,
NextState_Id int NOT NULL,
Probability float NOT NULL
);
My classes:
public class MarkovState
{
public vir开发者_如何学Pythontual int Id { get; private set; }
public virtual string StateContent { get; set; }
public virtual IDictionary<int, TransitionProbability> TransitionProbabilities { get; set; }
}
public class TransitionProbability
{
public virtual int Id { get; private set; }
public virtual MarkovState CurrentState { get; set; }
public virtual MarkovState NextState { get; set; }
public virtual float Probability { get; set; }
}
And my maps:
class MarkovStateMap : ClassMap<MarkovState>
{
public MarkovStateMap()
{
Id(x => x.Id);
Map(x => x.StateContent);
HasMany<TransitionProbability>(x => x.TransitionProbabilities)
.AsMap(x => x.NextState.Id)
.KeyColumn("CurrentState_Id")
.Not.LazyLoad()
.Inverse();
}
}
class TransitionProbabilityMap : ClassMap<TransitionProbability>
{
public TransitionProbabilityMap()
{
Id(x => x.Id);
Map(x => x.Probability);
References(x => x.CurrentState);
References(x => x.NextState);
}
}
However, this mapping seems to use CurrentState as the key, and not the NextState. I don't even know if this model is possible. Please suggest alternatives if you think this model isn't valid.
Maybe I'm misunderstanding the question, but your HasMany mapping points to CurrentState_Id. I think you're mappings should look like:
class MarkovStateMap : ClassMap<MarkovState>
{
public MarkovStateMap()
{
Id(x => x.Id);
Map(x => x.StateContent);
HasMany<TransitionProbability>(x => x.TransitionProbabilities)
.AsMap(x => x.NextState.Id)
.KeyColumn("NextState_Id")
.Not.LazyLoad()
.Inverse();
}
}
class TransitionProbabilityMap : ClassMap<TransitionProbability>
{
public TransitionProbabilityMap()
{
Id(x => x.Id);
Map(x => x.Probability);
References(x => x.CurrentState, "Id");
References(x => x.NextState, "Id");
}
}
加载中,请稍侯......
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