protected AbstractModel(Context[] parameters, IndexHashTable <string> map, string[] outcomeNames)
{
this.map = map;
this.outcomeNames = outcomeNames;
evalParameters = new EvalParameters(parameters, outcomeNames.Length);
}
protected AbstractModel(
Context[] parameters,
string[] predLabels,
string[] outcomeNames,
int correctionConstant,
double correctionParam) : this(predLabels, outcomeNames) {
evalParameters = new EvalParameters(parameters, correctionParam, correctionConstant, outcomeNames.Length);
}
protected AbstractModel(
Context[] parameters,
string[] predLabels,
string[] outcomeNames,
int correctionConstant,
double correctionParam) : this(predLabels, outcomeNames)
{
evalParameters = new EvalParameters(parameters, correctionParam, correctionConstant, outcomeNames.Length);
}
/// <summary>
/// Use this model to evaluate a context and return an array of the likelihood of each outcome given the specified context and the specified parameters.
/// </summary>
/// <param name="context">The integer values of the predicates which have been observed at the present decision point.</param>
/// <param name="values">The values for each of the parameters.</param>
/// <param name="prior">The prior distribution for the specified context.</param>
/// <param name="evalParams">The set of parameters used in this computation.</param>
/// <returns>
/// The normalized probabilities for the outcomes given the context.
/// The indexes of the double[] are the outcome ids, and the actual
/// string representation of the outcomes can be obtained from the
/// method getOutcome(int i).
/// </returns>
public static double[] Eval(int[] context, float[] values, double[] prior, EvalParameters evalParams) {
var numfeats = new int[evalParams.NumOutcomes];
double value = 1;
for (int ci = 0; ci < context.Length; ci++) {
if (context[ci] >= 0) {
var activeParameters = evalParams.Parameters[context[ci]].Parameters;
if (values != null) {
value = values[ci];
}
for (int ai = 0; ai < evalParams.Parameters[context[ci]].Outcomes.Length; ai++) {
int oid = evalParams.Parameters[context[ci]].Outcomes[ai];
numfeats[oid]++;
prior[oid] += activeParameters[ai]*value;
}
}
}
double normal = 0.0;
for (int oid = 0; oid < evalParams.NumOutcomes; oid++) {
if (!evalParams.CorrectionParam.Equals(0d)) {
//prior[oid] = Math.Exp(prior[oid] * model.ConstantInverse + ((1.0 - (numfeats[oid]/model.CorrectionConstant)) * model.CorrectionParam));
prior[oid] = Math.Exp(prior[oid] * evalParams.ConstantInverse + ((1.0 - (numfeats[oid] / evalParams.CorrectionConstant)) * evalParams.CorrectionParam));
} else {
prior[oid] = Math.Exp(prior[oid] * evalParams.ConstantInverse);
}
normal += prior[oid];
}
for (int oid = 0; oid < evalParams.NumOutcomes; oid++) {
prior[oid] /= normal;
}
return prior;
}
/// <summary>
/// Use this model to evaluate a context and return an array of the likelihood of each outcome given the specified context and the specified parameters.
/// </summary>
/// <param name="context">The integer values of the predicates which have been observed at the present decision point.</param>
/// <param name="prior">The prior distribution for the specified context.</param>
/// <param name="evalParams">The set of parameters used in this computation.</param>
/// <returns>
/// The normalized probabilities for the outcomes given the context.
/// The indexes of the double[] are the outcome ids, and the actual
/// string representation of the outcomes can be obtained from the
/// method getOutcome(int i).
/// </returns>
public static double[] Eval(int[] context, double[] prior, EvalParameters evalParams) {
return Eval(context, null, prior, evalParams);
}
/// <summary>
/// Use this model to evaluate a context and return an array of the likelihood of each outcome given that context.
/// </summary>
/// <param name="context">The names of the predicates which have been observed at the present decision point.</param>
/// <param name="values">This is where the distribution is stored.</param>
/// <param name="prior">The prior distribution for the specified context.</param>
/// <param name="evalParams">The set of parameters used in this computation.</param>
/// <param name="normalize">if set to <c>true</c> the probabilities will be normalized.</param>
/// <returns>The normalized probabilities for the outcomes given the context.
/// The indexes of the double[] are the outcome ids, and the actual string representation of
/// the outcomes can be obtained from the method getOutcome(int i).</returns>
public static double[] Eval(int[] context, float[] values, double[] prior, EvalParameters evalParams, bool normalize) {
double value = 1;
for (var ci = 0; ci < context.Length; ci++) {
if (context[ci] >= 0) {
var predParams = evalParams.Parameters[context[ci]];
var activeOutcomes = predParams.Outcomes;
var activeParameters = predParams.Parameters;
if (values != null) {
value = values[ci];
}
for (var ai = 0; ai < activeOutcomes.Length; ai++) {
var oid = activeOutcomes[ai];
prior[oid] += activeParameters[ai]*value;
}
}
}
if (!normalize)
return prior;
var numOutcomes = evalParams.NumOutcomes;
double maxPrior = 1;
for (var oid = 0; oid < numOutcomes; oid++) {
if (maxPrior < Math.Abs(prior[oid]))
maxPrior = Math.Abs(prior[oid]);
}
var normal = 0.0;
for (var oid = 0; oid < numOutcomes; oid++) {
prior[oid] = Math.Exp(prior[oid]/maxPrior);
normal += prior[oid];
}
for (var oid = 0; oid < numOutcomes; oid++)
prior[oid] /= normal;
return prior;
}
protected AbstractModel(Context[] parameters, string[] predLabels, string[] outcomeNames)
: this(predLabels, outcomeNames)
{
evalParameters = new EvalParameters(parameters, outcomeNames.Length);
}
protected AbstractModel(Context[] parameters, string[] predLabels, IndexHashTable<string> map, string[] outcomeNames) {
this.map = map;
this.outcomeNames = outcomeNames;
evalParameters = new EvalParameters(parameters, outcomeNames.Length);
}
protected AbstractModel(Context[] parameters, string[] predLabels, string[] outcomeNames)
: this(predLabels, outcomeNames) {
evalParameters = new EvalParameters(parameters, outcomeNames.Length);
}
private MutableContext[] FindParameters(int iterations, bool useAverage) {
info.Append(" Number of Iterations: {0}\n", iterations);
Display("\nPerforming " + iterations + " iterations.\n");
var allOutcomesPattern = new int[numOutcomes];
for (var oi = 0; oi < numOutcomes; oi++)
allOutcomesPattern[oi] = oi;
/** Stores the estimated parameter value of each predicate during iteration. */
var param = new MutableContext[numPreds];
for (var pi = 0; pi < numPreds; pi++) {
param[pi] = new MutableContext(allOutcomesPattern, new double[numOutcomes]);
for (var aoi = 0; aoi < numOutcomes; aoi++)
param[pi].SetParameter(aoi, 0.0);
}
// ReSharper disable once CoVariantArrayConversion
var evalParams = new EvalParameters(param, numOutcomes);
// Stores the sum of parameter values of each predicate over many iterations.
var summedParams = new MutableContext[numPreds];
if (useAverage) {
for (var pi = 0; pi < numPreds; pi++) {
summedParams[pi] = new MutableContext(allOutcomesPattern, new double[numOutcomes]);
for (var aoi = 0; aoi < numOutcomes; aoi++)
summedParams[pi].SetParameter(aoi, 0.0);
}
}
// Keep track of the previous three accuracies. The difference of
// the mean of these and the current training set accuracy is used
// with tolerance to decide whether to stop.
var prevAccuracy1 = 0.0;
var prevAccuracy2 = 0.0;
var prevAccuracy3 = 0.0;
// A counter for the denominator for averaging.
var numTimesSummed = 0;
double stepSize = 1;
for (var i = 1; i <= iterations; i++) {
// Decrease the step size by a small amount.
if (stepSizeDecrease > 0)
stepSize *= 1 - stepSizeDecrease;
if (Monitor != null && Monitor.Token.CanBeCanceled)
Monitor.Token.ThrowIfCancellationRequested();
var numCorrect = 0;
for (var ei = 0; ei < numUniqueEvents; ei++) {
var targetOutcome = outcomeList[ei];
for (var ni = 0; ni < numTimesEventsSeen[ei]; ni++) {
// Compute the model's prediction according to the current parameters.
var modelDistribution = new double[numOutcomes];
PerceptronModel.Eval(
contexts[ei],
values != null ? values[ei] : null,
modelDistribution,
evalParams, false);
var maxOutcome = MaxIndex(modelDistribution);
// If the predicted outcome is different from the target
// outcome, do the standard update: boost the parameters
// associated with the target and reduce those associated
// with the incorrect predicted outcome.
if (maxOutcome != targetOutcome) {
for (var ci = 0; ci < contexts[ei].Length; ci++) {
var pi = contexts[ei][ci];
if (values == null) {
param[pi].UpdateParameter(targetOutcome, stepSize);
param[pi].UpdateParameter(maxOutcome, -stepSize);
} else {
param[pi].UpdateParameter(targetOutcome, stepSize*values[ei][ci]);
param[pi].UpdateParameter(maxOutcome, -stepSize*values[ei][ci]);
}
}
}
// Update the counts for accuracy.
if (maxOutcome == targetOutcome)
numCorrect++;
}
}
// Calculate the training accuracy and display.
var trainingAccuracy = (double) numCorrect/numEvents;
Display(string.Format("{0,-4} {1} of {2} - {3}",
i,
numCorrect,
numEvents,
trainingAccuracy));
// TODO: Make averaging configurable !!!
bool doAveraging;
if (useAverage && UseSkippedAveraging && (i < 20 || IsPerfectSquare(i))) {
doAveraging = true;
} else if (useAverage) {
doAveraging = true;
} else {
doAveraging = false;
}
if (doAveraging) {
numTimesSummed++;
for (var pi = 0; pi < numPreds; pi++)
for (var aoi = 0; aoi < numOutcomes; aoi++)
summedParams[pi].UpdateParameter(aoi, param[pi].Parameters[aoi]);
}
// If the tolerance is greater than the difference between the
// current training accuracy and all of the previous three
// training accuracies, stop training.
if (Math.Abs(prevAccuracy1 - trainingAccuracy) < tolerance &&
Math.Abs(prevAccuracy2 - trainingAccuracy) < tolerance &&
Math.Abs(prevAccuracy3 - trainingAccuracy) < tolerance) {
Display("Stopping: change in training set accuracy less than " + tolerance + "\n");
break;
}
// Update the previous training accuracies.
prevAccuracy1 = prevAccuracy2;
prevAccuracy2 = prevAccuracy3;
prevAccuracy3 = trainingAccuracy;
}
// Output the final training stats.
TrainingStats(evalParams);
if (!useAverage)
return param;
if (numTimesSummed == 0) // Improbable but possible according to the Coverity.
numTimesSummed = 1;
// Create averaged parameters
for (var pi = 0; pi < numPreds; pi++)
for (var aoi = 0; aoi < numOutcomes; aoi++)
summedParams[pi].SetParameter(aoi, summedParams[pi].Parameters[aoi]/numTimesSummed);
return summedParams;
}
private void TrainingStats(EvalParameters evalParams) {
var numCorrect = 0;
for (var ei = 0; ei < numUniqueEvents; ei++) {
for (var ni = 0; ni < numTimesEventsSeen[ei]; ni++) {
var modelDistribution = new double[numOutcomes];
PerceptronModel.Eval(
contexts[ei],
values != null ? values[ei] : null,
modelDistribution,
evalParams,
false);
var max = MaxIndex(modelDistribution);
if (max == outcomeList[ei])
numCorrect++;
}
}
var trainingAccuracy = (double) numCorrect/numEvents;
info.Append(" Correct Events: {0}\n" +
" Total Events: {1}\n" +
" Accuracy: {2}\n", numCorrect, numEvents, trainingAccuracy);
Display("\nPerceptron training complete:\n");
Display("\t Correct Events : " + numCorrect);
Display("\t Total Events : " + numEvents);
Display("\t Accuracy : " + trainingAccuracy);
}