Indeed, it's being tracked here:
https://issues.apache.org/jira/browse/SPARK-18230 though no Pr has been
opened yet.
On Tue, 6 Dec 2016 at 13:36 chris snow <chsnow...@gmail.com> wrote:
> I'm using the MatrixFactorizationModel.predict() method and encountered
> the following exception:
>
> Name: java.util.NoSuchElementException
> Message: next on empty iterator
> StackTrace: scala.collection.Iterator$$anon$2.next(Iterator.scala:39)
> scala.collection.Iterator$$anon$2.next(Iterator.scala:37)
> scala.collection.IndexedSeqLike$Elements.next(IndexedSeqLike.scala:64)
> scala.collection.IterableLike$class.head(IterableLike.scala:91)
>
> scala.collection.mutable.ArrayBuffer.scala$collection$IndexedSeqOptimized$$super$head(ArrayBuffer.scala:47)
>
> scala.collection.IndexedSeqOptimized$class.head(IndexedSeqOptimized.scala:120)
> scala.collection.mutable.ArrayBuffer.head(ArrayBuffer.scala:47)
>
> org.apache.spark.mllib.recommendation.MatrixFactorizationModel.predict(MatrixFactorizationModel.scala:81)
>
> $line78.$read$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:74)
>
> $line78.$read$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:79)
>
> $line78.$read$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:81)
>
> $line78.$read$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:83)
>
> $line78.$read$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:85)
>
> $line78.$read$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:87)
> $line78.$read$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:89)
> $line78.$read$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:91)
> $line78.$read$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:93)
> $line78.$read$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:95)
> $line78.$read$$iwC$$iwC$$iwC$$iwC.<init>(<console>:97)
> $line78.$read$$iwC$$iwC$$iwC.<init>(<console>:99)
> $line78.$read$$iwC$$iwC.<init>(<console>:101)
> $line78.$read$$iwC.<init>(<console>:103)
> $line78.$read.<init>(<console>:105)
> $line78.$read$.<init>(<console>:109)
> $line78.$read$.<clinit>(<console>)
> $line78.$eval$.<init>(<console>:7)
> $line78.$eval$.<clinit>(<console>)
> $line78.$eval.$print(<console>)
> sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:95)
>
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:55)
> java.lang.reflect.Method.invoke(Method.java:507)
> org.apache.spark.repl.SparkIMain$ReadEvalPrint.call(SparkIMain.scala:1065)
> org.apache.spark.repl.SparkIMain$Request.loadAndRun(SparkIMain.scala:1346)
> org.apache.spark.repl.SparkIMain.loadAndRunReq$1(SparkIMain.scala:840)
> org.apache.spark.repl.SparkIMain.interpret(SparkIMain.scala:871)
> org.apache.spark.repl.SparkIMain.interpret(SparkIMain.scala:819)
>
> com.ibm.spark.interpreter.ScalaInterpreter$$anonfun$interpretAddTask$1$$anonfun$apply$3.apply(ScalaInterpreter.scala:296)
>
> com.ibm.spark.interpreter.ScalaInterpreter$$anonfun$interpretAddTask$1$$anonfun$apply$3.apply(ScalaInterpreter.scala:291)
> com.ibm.spark.global.StreamState$.withStreams(StreamState.scala:80)
>
> com.ibm.spark.interpreter.ScalaInterpreter$$anonfun$interpretAddTask$1.apply(ScalaInterpreter.scala:290)
>
> com.ibm.spark.interpreter.ScalaInterpreter$$anonfun$interpretAddTask$1.apply(ScalaInterpreter.scala:290)
>
> com.ibm.spark.utils.TaskManager$$anonfun$add$2$$anon$1.run(TaskManager.scala:123)
>
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1153)
>
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
> java.lang.Thread.run(Thread.java:785)
>
> This took some debugging to figure out why I received the Exception, but
> when looking at the predict() implementation, I seems to assume that there
> will always be features found for the provided user and product ids:
>
>
> /** Predict the rating of one user for one product. */
> @Since("0.8.0")
> def predict(user: Int, product: Int): Double = {
> val userVector = userFeatures.lookup(user).head
> val productVector = productFeatures.lookup(product).head
> blas.ddot(rank, userVector, 1, productVector, 1)
> }
>
> It would be helpful if a more useful exception was raised, e.g.
>
> MissingUserFeatureException : "User ID ${user} not found in model"
> MissingProductFeatureException : "Product ID ${product} not found in model"
>
> WDYT?
>
>
>
>
