在Scala中使用Figaro时的com.cra.figaro.algorithm.NotATargetException

Question

当我试图运行我的代码时，我只是遇到了以下错误。我不明白我做错了什么。有什么建议吗？

com.cra.figaro.algorithm.NotATargetException
    at com.cra.figaro.algorithm.ProbQueryAlgorithm$class.check(ProbQueryAlgorithm.scala:68)
    at com.cra.figaro.algorithm.ProbQueryAlgorithm$class.probability(ProbQueryAlgorithm.scala:138)
    at com.cra.figaro.algorithm.sampling.WeightedSampler.probability(WeightedSampler.scala:25)
    at prob1.BetaBinomial$.runner1(BetaBinomial.scala:24)

我用runner1("HHHHTHHHHHHTHHTHHHTHH")在SBT中执行，我在figaro中有其他的代码正在工作，但是这个代码不能启动。

package prob1

import com.cra.figaro.library.atomic.continuous.Beta
import com.cra.figaro.library.atomic.discrete.Binomial
import com.cra.figaro.language.Flip
import com.cra.figaro.algorithm.sampling.Importance

object BetaBinomial {
    def runner1(data: String){
      val outcomes = data
      val numTosses = outcomes.length
      val numObservedHeads = outcomes.count((c: Char) => c == 'H')
      val bias = Beta(2,5)
      val numberOfHeads = Binomial(numTosses, bias)
      val nextToss = Flip(bias)

      numberOfHeads.observe(numObservedHeads)
      val algorithm = Importance(bias) 
      algorithm.start()
      Thread.sleep(1000)
      algorithm.stop()
      //This is where i get the error
      val probHeads = algorithm.probability(nextToss, true)
      println("Probability of heads = " + probHeads)
      algorithm.kill()
      numberOfHeads.unobserve()
    }
}

Answer 1

我不熟悉figaro，但是查看ProbQueryAlgorithm.check的实现表明您指定的目标不是queryTargets的一部分。queryTargets在Importance/WeightedSampler的构造函数中初始化

abstract class WeightedSampler(override val universe: Universe, targets: Element[_]*) extends ProbQueryAlgorithm with Sampler {
  lazy val queryTargets = targets.toList
  ...
}

abstract class Importance(universe: Universe, targets: Element[_]*)
  extends WeightedSampler(universe, targets: _*) {
  ...
}

你试过这个吗？

val algorithm = Importance(bias, nextToss)