/// <summary>
/// VMP message to 'd'
/// </summary>
/// <param name="exp">Incoming message from 'exp'. Must be a proper distribution. If uniform, the result will be uniform.</param>
/// <param name="d">Incoming message from 'd'. Must be a proper distribution. If uniform, the result will be uniform.</param>
/// <param name="to_d">Previous outgoing message to 'd'.</param>
/// <returns>The outgoing VMP message to the 'd' argument</returns>
/// <remarks><para>
/// The outgoing message is the factor viewed as a function of 'd' with 'exp' integrated out.
/// The formula is <c>sum_exp p(exp) factor(exp,d)</c>.
/// </para></remarks>
/// <exception cref="ImproperMessageException"><paramref name="exp"/> is not a proper distribution</exception>
/// <exception cref="ImproperMessageException"><paramref name="d"/> is not a proper distribution</exception>
public static Gaussian DAverageLogarithm([Proper] Gamma exp, [Proper, Stochastic] Gaussian d, Gaussian to_d)
{
if (exp.IsPointMass)
{
return(ExpOp.DAverageLogarithm(exp.Point));
}
double m, v;
d.GetMeanAndVariance(out m, out v);
Gaussian msg = new Gaussian();
double mu, s2;
var prior = d / to_d;
prior.GetMeanAndVariance(out mu, out s2);
var z = Vector.Zero(2);
z[0] = m;
z[1] = Math.Log(v);
double startingValue = GradientAndValueAtPoint(mu, s2, z, exp.Shape, exp.Rate, null);
var s = new BFGS();
int evalCounter = 0;
s.MaximumStep = 1e3;
s.MaximumIterations = 100;
s.Epsilon = 1e-5;
s.convergenceCriteria = BFGS.ConvergenceCriteria.Objective;
z = s.Run(z, 1.0, delegate(Vector y, ref Vector grad) { evalCounter++; return(GradientAndValueAtPoint(mu, s2, y, exp.Shape, exp.Rate, grad)); });
m = z[0];
v = Math.Exp(z[1]);
to_d.SetMeanAndVariance(m, v);
to_d.SetToRatio(to_d, prior);
double endValue = GradientAndValueAtPoint(mu, s2, z, exp.Shape, exp.Rate, null);
//Console.WriteLine("Went from {0} to {1} in {2} steps, {3} evals", startingValue, endValue, s.IterationsPerformed, evalCounter);
if (startingValue < endValue)
{
Console.WriteLine("Warning: BFGS resulted in an increased objective function");
}
return(to_d);
/* ---------------- NEWTON ITERATION VERSION 1 -------------------
* double meanTimesPrec, prec;
* d.GetNatural(out meanTimesPrec, out prec);
* Matrix K = new Matrix(2, 2);
* K[0, 0]=1/prec; // d2K by dmu^2
* K[1, 0]=K[0, 1]=-meanTimesPrec/(prec*prec);
* K[1, 1]=meanTimesPrec*meanTimesPrec/Math.Pow(prec, 3)+1/(2*prec*prec);
* double[,,] Kprime = new double[2, 2, 2];
* Kprime[0, 0, 0]=0;
* Kprime[0, 0, 1]=Kprime[0, 1, 0]=Kprime[1, 0, 0]=-1/(prec*prec);
* Kprime[0, 1, 1]=Kprime[1, 1, 0]=Kprime[1, 0, 1]=2*meanTimesPrec/Math.Pow(prec, 3);
* Kprime[1, 1, 1]=-3*meanTimesPrec*meanTimesPrec/Math.Pow(prec, 4)-1/Math.Pow(prec, 3);
* Vector gradS = new Vector(2);
* gradS[0]=(exp.Shape-1)/prec-exp.Rate/prec*Math.Exp((meanTimesPrec+.5)/prec);
* gradS[1]=-(exp.Shape-1)*meanTimesPrec/(prec*prec)+exp.Rate*(meanTimesPrec+.5)/(prec*prec)*Math.Exp((meanTimesPrec+.5)/prec);
* Matrix grad2S = new Matrix(2, 2);
* grad2S[0, 0]=-exp.Rate/(prec*prec)*Math.Exp((meanTimesPrec+.5)/prec);
* grad2S[0, 1]=grad2S[1, 0]=-(exp.Shape-1)/(prec*prec)+exp.Rate*(1/(prec*prec)+(meanTimesPrec+.5)/Math.Pow(prec, 3))*Math.Exp((meanTimesPrec+.5)/prec);
* grad2S[1, 1]=2*(exp.Shape-1)*meanTimesPrec/Math.Pow(prec, 3)-exp.Rate*(meanTimesPrec+.5)/(prec*prec)*(2/prec+(meanTimesPrec+.5)/(prec*prec))*Math.Exp((meanTimesPrec+.5)/prec);
* Vector phi = new Vector(new double[] { result.MeanTimesPrecision, result.Precision });
* Vector gradKL = K*phi-gradS;
* Matrix hessianKL = K - grad2S;
* for (int i=0; i<2; i++)
* for (int j=0; j<2; j++)
* for (int k=0; k<2; k++)
* hessianKL[i, j]+=Kprime[i, j, k]*phi[k];
* double step = 1;
* Vector direction = GammaFromShapeAndRate.twoByTwoInverse(hessianKL)*gradKL;
* Vector newPhi = phi - step * direction;
* result.SetNatural(newPhi[0], newPhi[1]);
* return result;
*
* ---------------- NEWTON ITERATION VERSION 2 -------------------
* double mean, variance;
* d.GetMeanAndVariance(out mean, out variance);
* Gaussian prior = d / result;
* double mean1, variance1;
* prior.GetMeanAndVariance(out mean1, out variance1);
* Vector gradKL = new Vector(2);
* gradKL[0]=-(exp.Shape-1)+exp.Rate*Math.Exp(mean+variance/2)+mean/variance1-mean1/variance1;
* gradKL[1]=-1/(2*variance)+exp.Rate*Math.Exp(mean+variance/2)+1/(2*variance1);
* Matrix hessianKL = new Matrix(2, 2);
* hessianKL[0, 0]=exp.Rate*Math.Exp(mean+variance/2)+1/variance1;
* hessianKL[0, 1]=hessianKL[1, 0]=.5*exp.Rate*Math.Exp(mean+variance/2);
* hessianKL[1, 1]=1/(2*variance*variance)+exp.Rate*Math.Exp(mean+variance/2)/4;
* result.GetMeanAndVariance(out mean, out variance);
* if (double.IsInfinity(variance))
* variance=1000;
* Vector theta = new Vector(new double[] { mean, variance });
* theta -= GammaFromShapeAndRate.twoByTwoInverse(hessianKL)*gradKL;
* result.SetMeanAndVariance(theta[0], theta[1]);
* return result;
* ----------------------------------------------------------------- */
}
/// <summary>EP message to <c>log</c>.</summary>
/// <param name="log">Incoming message from <c>log</c>. Must be a proper distribution. If uniform, the result will be uniform.</param>
/// <param name="d">Incoming message from <c>d</c>. Must be a proper distribution. If uniform, the result will be uniform.</param>
/// <param name="result">Modified to contain the outgoing message.</param>
/// <returns>
/// <paramref name="result" />
/// </returns>
/// <remarks>
/// <para>The outgoing message is a distribution matching the moments of <c>log</c> as the random arguments are varied. The formula is <c>proj[p(log) sum_(d) p(d) factor(log,d)]/p(log)</c>.</para>
/// </remarks>
/// <exception cref="ImproperMessageException">
/// <paramref name="log" /> is not a proper distribution.</exception>
/// <exception cref="ImproperMessageException">
/// <paramref name="d" /> is not a proper distribution.</exception>
public static Gaussian LogAverageConditional([Proper] Gaussian log, [SkipIfUniform] Gamma d, Gaussian result)
{
var g = Gamma.FromShapeAndRate(d.Shape + 1, d.Rate);
return(ExpOp.DAverageConditional(g, log, result));
}
/// <summary>Evidence message for EP.</summary>
/// <param name="log">Incoming message from <c>log</c>.</param>
/// <param name="d">Incoming message from <c>d</c>.</param>
/// <param name="to_log">Outgoing message to <c>log</c>.</param>
/// <returns>Logarithm of the factor's average value across the given argument distributions.</returns>
/// <remarks>
/// <para>The formula for the result is <c>log(sum_(log,d) p(log,d) factor(log,d))</c>.</para>
/// </remarks>
public static double LogAverageFactor(Gaussian log, Gamma d, [Fresh] Gaussian to_log)
{
Gamma g = Gamma.FromShapeAndRate(d.Shape + 1, d.Rate);
return(d.Shape / d.Rate * ExpOp.LogAverageFactor(g, log, to_log));
}
/// <summary>EP message to <c>d</c>.</summary>
/// <param name="log">Incoming message from <c>log</c>. Must be a proper distribution. If uniform, the result will be uniform.</param>
/// <param name="d">Incoming message from <c>d</c>.</param>
/// <param name="to_log">Previous outgoing message to <c>log</c>.</param>
/// <returns>The outgoing EP message to the <c>d</c> argument.</returns>
/// <remarks>
/// <para>The outgoing message is a distribution matching the moments of <c>d</c> as the random arguments are varied. The formula is <c>proj[p(d) sum_(log) p(log) factor(log,d)]/p(d)</c>.</para>
/// </remarks>
/// <exception cref="ImproperMessageException">
/// <paramref name="log" /> is not a proper distribution.</exception>
public static Gamma DAverageConditional([Proper] Gaussian log, Gamma d, Gaussian to_log)
{
var g = Gamma.FromShapeAndRate(d.Shape + 1, d.Rate);
return(ExpOp.ExpAverageConditional(g, log, to_log));
}
