当前位置: 首页>>代码示例>>C#>>正文


C# Gaussian.GetLogAverageOfPower方法代码示例

本文整理汇总了C#中Gaussian.GetLogAverageOfPower方法的典型用法代码示例。如果您正苦于以下问题:C# Gaussian.GetLogAverageOfPower方法的具体用法?C# Gaussian.GetLogAverageOfPower怎么用?C# Gaussian.GetLogAverageOfPower使用的例子?那么, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在Gaussian的用法示例。


在下文中一共展示了Gaussian.GetLogAverageOfPower方法的1个代码示例,这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞,您的评价将有助于系统推荐出更棒的C#代码示例。

示例1: LogAverageFactor

		/// <summary>
		/// Evidence message for EP
		/// </summary>
		/// <param name="logistic">Incoming message from 'logistic'.</param>
		/// <param name="x">Incoming message from 'x'.</param>
		/// <param name="falseMsg">Buffer 'falseMsg'.</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_(logistic,x) p(logistic,x) factor(logistic,x))</c>.
		/// </para></remarks>
		public static double LogAverageFactor(Beta logistic, Gaussian x, Gaussian falseMsg)
		{
			// return log(int_y int_x delta(y - Logistic(x)) Beta(y) Gaussian(x) dx dy)
			double m,v;
			x.GetMeanAndVariance(out m, out v);
			if (logistic.TrueCount == 2 && logistic.FalseCount == 1) {
				// shortcut for common case
				return Math.Log(2*MMath.LogisticGaussian(m, v));
			} else if (logistic.TrueCount == 1 && logistic.FalseCount == 2) {
				return Math.Log(2*MMath.LogisticGaussian(-m, v));
			} else {
				// logistic(sigma(x)) N(x;m,v)
				// = sigma(x)^(a-1) sigma(-x)^(b-1) N(x;m,v) gamma(a+b)/gamma(a)/gamma(b)
				// = e^((a-1)x) sigma(-x)^(a+b-2) N(x;m,v)
				// = sigma(-x)^(a+b-2) N(x;m+(a-1)v,v) exp((a-1)m + (a-1)^2 v/2)
				// int_x logistic(sigma(x)) N(x;m,v) dx 
				// =approx (int_x sigma(-x)/falseMsg(x) falseMsg(x)^(a+b-2) N(x;m+(a-1)v,v))^(a+b-2) 
				//       * (int_x falseMsg(x)^(a+b-2) N(x;m+(a-1)v,v))^(1 - (a+b-2))
				//       *  exp((a-1)m + (a-1)^2 v/2) gamma(a+b)/gamma(a)/gamma(b)
				// This formula comes from (66) in Minka (2005)
				// Alternatively,
				// =approx (int_x falseMsg(x)/sigma(-x) falseMsg(x)^(a+b-2) N(x;m+(a-1)v,v))^(-(a+b-2))
				//       * (int_x falseMsg(x)^(a+b-2) N(x;m+(a-1)v,v))^(1 + (a+b-2))
				//       *  exp((a-1)m + (a-1)^2 v/2) gamma(a+b)/gamma(a)/gamma(b)
				double tc1 = logistic.TrueCount-1;
				double fc1 = logistic.FalseCount-1;
				Gaussian prior = new Gaussian(m + tc1*v, v);
				if (tc1+fc1 < 0) {
					// numerator2 = int_x falseMsg(x)^(a+b-1) N(x;m+(a-1)v,v) dx
					double numerator2 = prior.GetLogAverageOfPower(falseMsg, tc1+fc1+1);
					Gaussian prior2 = prior*(falseMsg^(tc1+fc1+1));
					double mp,vp;
					prior2.GetMeanAndVariance(out mp, out vp);
					// numerator = int_x (1+exp(x)) falseMsg(x)^(a+b-1) N(x;m+(a-1)v,v) dx / int_x falseMsg(x)^(a+b-1) N(x;m+(a-1)v,v) dx
					double numerator = Math.Log(1 + Math.Exp(mp + 0.5*vp));
					// denominator = int_x falseMsg(x)^(a+b-2) N(x;m+(a-1)v,v) dx
					double denominator = prior.GetLogAverageOfPower(falseMsg, tc1+fc1);
					return -(tc1+fc1)*(numerator+numerator2-denominator) + denominator + (tc1*m + tc1*tc1*v*0.5) - logistic.GetLogNormalizer();
				} else {
					// numerator2 = int_x falseMsg(x)^(a+b-3) N(x;m+(a-1)v,v) dx
					double numerator2 = prior.GetLogAverageOfPower(falseMsg, tc1+fc1-1);
					Gaussian prior2 = prior*(falseMsg^(tc1+fc1-1));
					double mp,vp;
					prior2.GetMeanAndVariance(out mp, out vp);
					// numerator = int_x sigma(-x) falseMsg(x)^(a+b-3) N(x;m+(a-1)v,v) dx / int_x falseMsg(x)^(a+b-3) N(x;m+(a-1)v,v) dx
					double numerator = Math.Log(MMath.LogisticGaussian(-mp, vp));
					// denominator = int_x falseMsg(x)^(a+b-2) N(x;m+(a-1)v,v) dx
					double denominator = prior.GetLogAverageOfPower(falseMsg, tc1+fc1);
					return (tc1+fc1)*(numerator+numerator2-denominator) + denominator + (tc1*m + tc1*tc1*v*0.5) - logistic.GetLogNormalizer();
				}
			}
		}
开发者ID:xornand,项目名称:Infer.Net,代码行数:62,代码来源:Logistic.cs


注:本文中的Gaussian.GetLogAverageOfPower方法示例由纯净天空整理自Github/MSDocs等开源代码及文档管理平台,相关代码片段筛选自各路编程大神贡献的开源项目,源码版权归原作者所有,传播和使用请参考对应项目的License;未经允许,请勿转载。