/// <summary>
/// Determines whether the specified <see cref="DecisionRule"/> is equal to this instance.
/// </summary>
///
/// <param name="other">The <see cref="DecisionRule"/> to compare with this instance.</param>
///
/// <returns>
/// <c>true</c> if the specified <see cref="DecisionRule"/>
/// is equal to this instance; otherwise, <c>false</c>.
/// </returns>
///
public bool Equals(DecisionRule other)
{
if ((object)other == null)
{
return(false);
}
return(this.Output == other.output &&
this.Antecedents.SetEquals(other.Antecedents));
}
/// <summary>
/// Compares this instance to another <see cref="DecisionRule"/>.
/// </summary>
///
public int CompareTo(DecisionRule other)
{
int order = this.Output.CompareTo(other.Output);
if (order == 0)
{
return(this.Antecedents.Count.CompareTo(other.Antecedents.Count));
}
return(order);
}
/// <summary>
/// Gets whether this rule and another rule have
/// the same antecedents but different outputs.
/// </summary>
///
/// <param name="rule"></param>
///
/// <returns>True if the two rules are contradictory;
/// false otherwise.</returns>
///
public bool IsInconsistentWith(DecisionRule rule)
{
return(Antecedents.SetEquals(rule.Antecedents) && Output != rule.Output);
}
/// <summary>
/// Computes the reduction algorithm.
/// </summary>
///
/// <param name="inputs">A set of training inputs.</param>
/// <param name="outputs">The outputs corresponding to each of the inputs.</param>
///
/// <returns>The average error after the reduction.</returns>
///
public double Compute(double[][] inputs, int[] outputs)
{
int samples = outputs.Length;
bool[] actual = new bool[samples];
bool[] expected = new bool[samples];
DecisionRule[] list = decisionList.ToArray();
var antecedents = new HashSet <Antecedent>();
foreach (DecisionRule rule in list)
{
foreach (Antecedent antecedent in rule)
{
antecedents.Add(antecedent);
}
}
// 1. Eliminate unnecessary antecedents
for (int y = 0; y < decisionList.OutputClasses; y++)
{
for (int i = 0; i < outputs.Length; i++)
{
expected[i] = outputs[i] == y;
}
var unnecessary = new HashSet <Antecedent>();
/*foreach (var rule in list)
* {
* if (rule.Output != y)
* continue;
*/
foreach (var antecedent in antecedents)
{
for (int i = 0; i < inputs.Length; i++)
{
actual[i] = antecedent.Match(inputs[i]);
}
if (CanEliminate(actual, expected))
{
unnecessary.Add(antecedent);
}
}
//}
foreach (var antecedent in unnecessary)
{
foreach (var rule in list)
{
if (rule.Output == y)
{
rule.Antecedents.Remove(antecedent);
}
}
}
}
bool[][] matches = new bool[list.Length][];
int[] counts = new int[list.Length];
for (int i = 0; i < matches.Length; i++)
{
DecisionRule rule = list[i];
matches[i] = new bool[outputs.Length];
for (int j = 0; j < inputs.Length; j++)
{
matches[i][j] = rule.Match(inputs[j]);
if (matches[i][j])
{
counts[i]++;
}
}
}
// double start = computeError(inputs, outputs, list);
for (int i = 0; i < list.Length; i++)
{
if (list[i] == null)
{
continue;
}
for (int j = 0; j < list.Length; j++)
{
if (list[i] == null)
{
break;
}
if (list[j] == null)
{
continue;
}
if (list[i].IsInconsistentWith(list[j]))
{
if (counts[i] > counts[j])
{
list[j] = null;
counts[j] = 0;
}
else
{
list[i] = null;
counts[i] = 0;
}
}
}
}
list = list.Distinct(allowNulls: false);
List <DecisionRule> newList = new List <DecisionRule>(list);
// double middle = computeError(inputs, outputs, list);
// 2. Eliminate redundant rules from the set
for (int y = 0; y < decisionList.OutputClasses; y++)
{
for (int i = 0; i < outputs.Length; i++)
{
expected[i] = outputs[i] == y;
}
var unnecessary = new HashSet <DecisionRule>();
foreach (var rule in newList)
{
if (rule.Output != y)
{
continue;
}
for (int i = 0; i < inputs.Length; i++)
{
actual[i] = rule.Match(inputs[i]);
}
if (CanEliminate(actual, expected))
{
unnecessary.Add(rule);
}
}
foreach (var rule in unnecessary)
{
newList.Remove(rule);
}
}
// double final = computeError(inputs, outputs, newList);
decisionList.Clear();
decisionList.AddRange(newList);
// Compute new decision error
double newError = ComputeError(inputs, outputs);
return(newError);
}
