Spark&x2B;Scala:NaiveBayes.train-异常为java.util.NoSuchElementException:next on empty迭代器
我正在尝试使用Spark MLlib的推文进行情绪分析。在预处理数据并将其转换为适当的格式后,我调用NaiveBayes的train方法来获取模型,但它失败了,出现了一个异常。以下是stacktrace:Spark&x2B;Scala:NaiveBayes.train-异常为java.util.NoSuchElementException:next on empty迭代器,scala,apache-spark,apache-spark-mllib,sentiment-analysis,naivebayes,Scala,Apache Spark,Apache Spark Mllib,Sentiment Analysis,Naivebayes,我正在尝试使用Spark MLlib的推文进行情绪分析。在预处理数据并将其转换为适当的格式后,我调用NaiveBayes的train方法来获取模型,但它失败了,出现了一个异常。以下是stacktrace: java.util.NoSuchElementException: next on empty iterator at scala.collection.Iterator$$anon$2.next(Iterator.scala:39) at scala.collection.I
java.util.NoSuchElementException: next on empty iterator
at scala.collection.Iterator$$anon$2.next(Iterator.scala:39)
at scala.collection.Iterator$$anon$2.next(Iterator.scala:37)
at scala.collection.IndexedSeqLike$Elements.next(IndexedSeqLike.scala:64)
at scala.collection.IterableLike$class.head(IterableLike.scala:91)
at scala.collection.mutable.ArrayOps$ofRef.scala$collection$IndexedSeqOptimized$$super$head(ArrayOps.scala:108)
at scala.collection.IndexedSeqOptimized$class.head(IndexedSeqOptimized.scala:120)
at scala.collection.mutable.ArrayOps$ofRef.head(ArrayOps.scala:108)
at org.apache.spark.mllib.classification.NaiveBayes.run(NaiveBayes.scala:408)
at org.apache.spark.mllib.classification.NaiveBayes$.train(NaiveBayes.scala:467)
at org.jc.sparknaivebayes.main.NaiveBayesTrain$delayedInit$body.apply(NaiveBayesTrain.scala:53)
at scala.Function0$class.apply$mcV$sp(Function0.scala:40)
at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
at scala.App$$anonfun$main$1.apply(App.scala:71)
at scala.App$$anonfun$main$1.apply(App.scala:71)
at scala.collection.immutable.List.foreach(List.scala:318)
at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:32)
at scala.App$class.main(App.scala:71)
at org.jc.sparknaivebayes.main.NaiveBayesTrain$.main(NaiveBayesTrain.scala:12)
at org.jc.sparknaivebayes.main.NaiveBayesTrain.main(NaiveBayesTrain.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.spark.deploy.yarn.ApplicationMaster$$anon$2.run(ApplicationMaster.scala:542)
这是我的主要方法:
val csvFiles = args(0).split(",")
val modelStore = args(1)
val docs = TweetParser.parseAll(csvFiles, sc)
val termDocs = Tokenizer.tokenizeAll(docs)
val termDocsRdd = sc.parallelize[TermDoc](termDocs.toSeq)
val numDocs = termDocsRdd.count()
//val terms = termDocsRdd.flatMap(_.terms).distinct().collect().sortBy(identity)
val terms = termDocsRdd.flatMap(_.terms).distinct().sortBy(identity)
val termDict = new Dictionary(terms)
//val labels = termDocsRdd.flatMap(_.labels).distinct().collect()
val labels = termDocsRdd.flatMap(_.labels).distinct()
val labelDict = new Dictionary(labels)
val idfs = (termDocsRdd.flatMap(termDoc => termDoc.terms.map((termDoc.doc, _))).distinct().groupBy(_._2) collect {
case (term, docs) if docs.size > 3 =>
term -> (numDocs.toDouble / docs.size.toDouble)
}).collect.toMap
val tfidfs = termDocsRdd flatMap {
termDoc =>
val termPairs: Seq[(Int, Double)] = termDict.tfIdfs(termDoc.terms, idfs)
termDoc.labels.headOption.map {
label =>
val labelId = labelDict.indexOf(label).toDouble
val vector = Vectors.sparse(termDict.count.toInt, termPairs)
LabeledPoint(labelId, vector)
}
}
val model = NaiveBayes.train(tfidfs)
字典类在这里:
class Dictionary(dict: RDD[String]) extends Serializable {
//val builder = ImmutableBiMap.builder[String, Long]()
//dict.zipWithIndex.foreach(e => builder.put(e._1, e._2))
//val termToIndex = builder.build()
val termToIndex = dict.zipWithIndex()
//@transient
//lazy val indexToTerm = termToIndex.inverse()
lazy val indexToTerm = dict.zipWithIndex().map{
case (k, v) => (v, k)
} //converts from (a, 0),(b, 1),(c, 2) to (0, a),(1, b),(2, c)
val count = termToIndex.count().toInt
def indexOf(term: String): Int = termToIndex.lookup(term).headOption.getOrElse[Long](-1).toInt
def valueOf(index: Int): String = indexToTerm.lookup(index).headOption.getOrElse("")
def tfIdfs (terms: Seq[String], idfs: Map[String, Double]): Seq[(Int, Double)] = {
val filteredTerms = terms.filter(idfs contains)
(filteredTerms.groupBy(identity).map {
case (term, instances) => {
val indexOfTerm: Int = indexOf(term)
if (indexOfTerm < 0) (-1, 0.0) else (indexOf(term), (instances.size.toDouble / filteredTerms.size.toDouble) * idfs(term))
}
}).filter(p => p._1.toInt >= 0).toSeq.sortBy(_._1)
}
def vectorize(tfIdfs: Iterable[(Int, Double)]) = {
Vectors.sparse(dict.count().toInt, tfIdfs.toSeq)
}
}
TermDoc类:
case class TermDoc(doc: String, labels: Set[String], terms: Seq[String])
我被困在这一步,我真的需要完成这项工作,但我有很多麻烦,在寻找有关它的有用信息。提前谢谢
附言:这是基于黑猩猩的博客:
更新:CSV解析器和文档生成器的新代码
import org.apache.spark.SparkContext
import scala.io.Source
/**
* Created by cespedjo on 14/02/2017.
*/
object TweetParser extends Serializable{
val headerPart = "polarity"
val mentionRegex = """@(.)+?\s""".r
val fullRegex = """(\d+),(.+?),(N|P|NEU|NONE)(,\w+|;\w+)*""".r
def parseAll(csvFiles: Iterable[String], sc: SparkContext) = csvFiles flatMap(csv => parse(csv, sc))
def parse(csvFile: String, sc: SparkContext) = {
val csv = sc.textFile(csvFile)
val docs = scala.collection.mutable.ArrayBuffer.empty[Document]
csv.foreach(
line => if (!line.contains(headerPart)) docs += buildDocument(line)
)
docs
//docs.filter(!_.docId.equals("INVALID"))
}
def buildDocument(line: String): Document = {
val fullRegex(id, txt, snt, opt) = line
if (id != null && txt != null && snt != null)
new Document(id, mentionRegex.replaceAllIn(txt, ""), Set(snt))
else
new Document("INVALID")
}
}
case class Document(docId: String, body: String = "", labels: Set[String] = Set.empty)
我认为问题在于有些文档不包含任何术语对。不能在空数据点上进行训练。尝试将代码更改为:
val tfidfs = termDocsRdd flatMap {
termDoc =>
val termPairs: Seq[(Int, Double)] = termDict.tfIdfs(termDoc.terms, idfs)
if (termPairs.nonEmpty) {
termDoc.labels.headOption.map {
label =>
val labelId = labelDict.indexOf(label).toDouble
val vector = Vectors.sparse(termDict.count.toInt, termPairs)
LabeledPoint(labelId, vector)
} else {
None
}
}
我认为你的错误来自于
val vector=Vectors.sparse中的空向量。你需要找到/发布所有指向你应用程序中已损坏代码的错误消息,这样你就可以确定,我有类似的问题,并通过向向量推送更多数据来解决,顺便说一句,你可能会查找sparse vector
类,还有你申请的更多细节谢谢你的评论Karol,我是spark和scala的新手,你能详细说明一下你的建议吗?我无法理解“将更多数据推送到矢量”部分,因为我认为它是由RDD中已经包含的数据填充的,所以缺少多少数据?顺便说一句,我查看了矢量的文档,它说本地矢量。。。这是否意味着它不能在分布式模式下使用?在分布式模式下运行时,我需要使用什么来进行监督学习?我使用ML管道,利用交叉验证器和参数转换功能:https://databricks.com/blog/2015/10/20/audience-modeling-with-apache-spark-ml-pipelines.html
,http://spark.apache.org/docs/latest/ml-pipeline.html
,重向量:在对该数据应用模型/函数之前,查看向量中的数据,错误表示没有数据/需要一些数据missing@KarolSudol你知道为什么问题中的代码更新会产生空RDD吗?我已经在CSV文件中的几行代码上进行了测试,它可以识别指定的模式,但是,没有文档附加到可变数组中。感谢您的回答Pascal,您知道问题中的代码更新为什么会产生空RDD吗?我已经在CSV文件的几行代码上进行了测试,它可以识别指定的模式,但是,没有文档附加到可变数组中。您似乎在某些地方更改了代码(注释内容)。。您正在查找一个字典,它是一个未收集的RDD,这是错误的,因为在代码中的这一点上,您需要有“全局视图”(即:您不希望在局部工作字典中进行查找,而是在全局字典中进行查找对我来说似乎是对的,但不是我理解的最新代码…但我想找到一种不使用collect来实现这一点的正确方法,因为我在某个地方读到,这不是一个好的选择,因为它会强制在驱动程序中收集数据,并且在处理大量数据时可能会导致错误…有什么建议吗?顺便说一句,行为执行这一行代码时会出现这种情况:val docs=TweetParser.parseAll(csvFiles,sc)。我已经用一个文件进行了测试,docs.size为0。我不知道为什么即使在单独的行上测试模式时也会出现这种情况。
val tfidfs = termDocsRdd flatMap {
termDoc =>
val termPairs: Seq[(Int, Double)] = termDict.tfIdfs(termDoc.terms, idfs)
if (termPairs.nonEmpty) {
termDoc.labels.headOption.map {
label =>
val labelId = labelDict.indexOf(label).toDouble
val vector = Vectors.sparse(termDict.count.toInt, termPairs)
LabeledPoint(labelId, vector)
} else {
None
}
}