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https://issues.apache.org/jira/browse/SPARK-13178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15132718#comment-15132718
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Xusen Yin commented on SPARK-13178:
-----------------------------------
Thanks! I'll try it.
> RRDD faces with concurrency issue in case of rdd.zip(rdd).count()
> -----------------------------------------------------------------
>
> Key: SPARK-13178
> URL: https://issues.apache.org/jira/browse/SPARK-13178
> Project: Spark
> Issue Type: Bug
> Components: SparkR
> Reporter: Xusen Yin
>
> In Kmeans algorithm, there is a zip operation before taking samples, i.e.
> https://github.com/apache/spark/blob/master/mllib/src/main/scala/org/apache/spark/mllib/clustering/KMeans.scala#L210,
> which can be simplified in the following code:
> {code:title=zip.scala|theme=FadeToGrey|linenumbers=true|language=scala|firstline=0001|collapse=false}
> val rdd = ...
> val rdd2 = rdd.map(x => x)
> rdd.zip(rdd2).count()
> {code}
> However, RRDD fails on this operation with an error of "can only zip rdd with
> same number of elements" or "stream closed", similar to the JIRA issue:
> https://issues.apache.org/jira/browse/SPARK-2251
> Inside RRDD, a data stream is used to ingest data from the R side. In the zip
> operation, zip with self computes each partition twice. So if we zip a
> HadoopRDD (iris dataset) with itself, we get
> {code:title=log-from-zip-HadoopRDD|theme=FadeToGrey|linenumbers=true|language=scala|firstline=0001|collapse=false}
> we get a pair (6.8, 6.8)
> we get a pair (5.1, 5.1)
> we get a pair (6.7, 6.7)
> we get a pair (4.9, 4.9)
> we get a pair (6.0, 6.0)
> we get a pair (4.7, 4.7)
> we get a pair (5.7, 5.7)
> we get a pair (4.6, 4.6)
> we get a pair (5.5, 5.5)
> we get a pair (5.0, 5.0)
> we get a pair (5.5, 5.5)
> we get a pair (5.4, 5.4)
> we get a pair (5.8, 5.8)
> we get a pair (4.6, 4.6)
> we get a pair (6.0, 6.0)
> we get a pair (5.0, 5.0)
> we get a pair (5.4, 5.4)
> we get a pair (4.4, 4.4)
> we get a pair (6.0, 6.0)
> we get a pair (4.9, 4.9)
> we get a pair (6.7, 6.7)
> we get a pair (5.4, 5.4)
> we get a pair (6.3, 6.3)
> we get a pair (4.8, 4.8)
> we get a pair (5.6, 5.6)
> we get a pair (4.8, 4.8)
> we get a pair (5.5, 5.5)
> we get a pair (4.3, 4.3)
> we get a pair (5.5, 5.5)
> we get a pair (5.8, 5.8)
> we get a pair (6.1, 6.1)
> we get a pair (5.7, 5.7)
> we get a pair (5.8, 5.8)
> we get a pair (5.4, 5.4)
> we get a pair (5.0, 5.0)
> we get a pair (5.1, 5.1)
> we get a pair (5.6, 5.6)
> we get a pair (5.7, 5.7)
> we get a pair (5.7, 5.7)
> we get a pair (5.1, 5.1)
> we get a pair (5.7, 5.7)
> we get a pair (5.4, 5.4)
> we get a pair (6.2, 6.2)
> we get a pair (5.1, 5.1)
> we get a pair (5.1, 5.1)
> we get a pair (4.6, 4.6)
> we get a pair (5.7, 5.7)
> we get a pair (5.1, 5.1)
> we get a pair (6.3, 6.3)
> we get a pair (4.8, 4.8)
> we get a pair (5.8, 5.8)
> we get a pair (5.0, 5.0)
> we get a pair (7.1, 7.1)
> we get a pair (5.0, 5.0)
> we get a pair (6.3, 6.3)
> we get a pair (5.2, 5.2)
> we get a pair (6.5, 6.5)
> we get a pair (5.2, 5.2)
> we get a pair (7.6, 7.6)
> we get a pair (4.7, 4.7)
> we get a pair (4.9, 4.9)
> we get a pair (4.8, 4.8)
> we get a pair (7.3, 7.3)
> we get a pair (5.4, 5.4)
> we get a pair (6.7, 6.7)
> we get a pair (5.2, 5.2)
> we get a pair (7.2, 7.2)
> we get a pair (5.5, 5.5)
> we get a pair (6.5, 6.5)
> we get a pair (4.9, 4.9)
> we get a pair (6.4, 6.4)
> we get a pair (5.0, 5.0)
> we get a pair (6.8, 6.8)
> we get a pair (5.5, 5.5)
> we get a pair (5.7, 5.7)
> we get a pair (4.9, 4.9)
> we get a pair (5.8, 5.8)
> we get a pair (4.4, 4.4)
> we get a pair (6.4, 6.4)
> we get a pair (5.1, 5.1)
> we get a pair (6.5, 6.5)
> we get a pair (5.0, 5.0)
> we get a pair (7.7, 7.7)
> we get a pair (4.5, 4.5)
> we get a pair (7.7, 7.7)
> we get a pair (4.4, 4.4)
> we get a pair (6.0, 6.0)
> we get a pair (5.0, 5.0)
> we get a pair (6.9, 6.9)
> we get a pair (5.1, 5.1)
> we get a pair (5.6, 5.6)
> we get a pair (4.8, 4.8)
> we get a pair (7.7, 7.7)
> we get a pair (6.3, 6.3)
> we get a pair (5.1, 5.1)
> we get a pair (6.7, 6.7)
> we get a pair (4.6, 4.6)
> we get a pair (7.2, 7.2)
> we get a pair (5.3, 5.3)
> we get a pair (6.2, 6.2)
> we get a pair (5.0, 5.0)
> we get a pair (6.1, 6.1)
> we get a pair (7.0, 7.0)
> we get a pair (6.4, 6.4)
> we get a pair (6.4, 6.4)
> we get a pair (7.2, 7.2)
> we get a pair (6.9, 6.9)
> we get a pair (7.4, 7.4)
> we get a pair (5.5, 5.5)
> we get a pair (7.9, 7.9)
> we get a pair (6.5, 6.5)
> we get a pair (6.4, 6.4)
> we get a pair (5.7, 5.7)
> we get a pair (6.3, 6.3)
> we get a pair (6.3, 6.3)
> we get a pair (6.1, 6.1)
> we get a pair (4.9, 4.9)
> we get a pair (7.7, 7.7)
> we get a pair (6.6, 6.6)
> we get a pair (6.3, 6.3)
> we get a pair (5.2, 5.2)
> we get a pair (6.4, 6.4)
> we get a pair (5.0, 5.0)
> we get a pair (6.0, 6.0)
> we get a pair (5.9, 5.9)
> we get a pair (6.9, 6.9)
> we get a pair (6.0, 6.0)
> we get a pair (6.7, 6.7)
> we get a pair (6.1, 6.1)
> we get a pair (6.9, 6.9)
> we get a pair (5.6, 5.6)
> we get a pair (5.8, 5.8)
> we get a pair (6.7, 6.7)
> we get a pair (6.8, 6.8)
> we get a pair (5.6, 5.6)
> we get a pair (6.7, 6.7)
> we get a pair (5.8, 5.8)
> we get a pair (6.7, 6.7)
> we get a pair (6.2, 6.2)
> we get a pair (6.3, 6.3)
> we get a pair (5.6, 5.6)
> we get a pair (6.5, 6.5)
> we get a pair (5.9, 5.9)
> we get a pair (6.2, 6.2)
> we get a pair (6.1, 6.1)
> we get a pair (5.9, 5.9)
> we get a pair (6.3, 6.3)
> we get a pair (6.1, 6.1)
> we get a pair (6.4, 6.4)
> we get a pair (6.6, 6.6)
> {code}
> However, in RRDD with the same setting we get:
> {code:title=log-from-zip-RRDD|theme=FadeToGrey|linenumbers=true|language=scala|firstline=0001|collapse=false}
> we get a pair (5.1, 5.1)
> we get a pair (4.9, 4.7)
> we get a pair (4.6, 5.0)
> we get a pair (5.4, 4.6)
> we get a pair (5.0, 4.4)
> we get a pair (4.9, 5.4)
> we get a pair (4.8, 4.8)
> we get a pair (4.3, 5.8)
> we get a pair (5.7, 5.4)
> we get a pair (5.1, 5.7)
> we get a pair (5.1, 5.4)
> we get a pair (5.1, 4.6)
> we get a pair (5.1, 4.8)
> we get a pair (5.0, 5.0)
> we get a pair (5.2, 5.2)
> we get a pair (4.7, 4.8)
> we get a pair (5.4, 5.2)
> we get a pair (5.5, 4.9)
> we get a pair (5.0, 5.5)
> we get a pair (4.9, 4.4)
> we get a pair (5.1, 5.0)
> we get a pair (4.5, 4.4)
> we get a pair (5.0, 5.1)
> we get a pair (4.8, 5.1)
> we get a pair (4.6, 5.3)
> we get a pair (5.0, 7.0)
> we get a pair (6.4, 6.9)
> we get a pair (5.5, 6.5)
> we get a pair (5.7, 6.3)
> we get a pair (4.9, 6.6)
> we get a pair (5.2, 5.0)
> we get a pair (5.9, 6.0)
> we get a pair (6.1, 5.6)
> we get a pair (6.7, 5.6)
> we get a pair (5.8, 6.2)
> we get a pair (5.6, 5.9)
> we get a pair (6.1, 6.3)
> we get a pair (6.1, 6.4)
> we get a pair (6.6, 6.8)
> we get a pair (6.7, 6.0)
> we get a pair (5.7, 5.5)
> we get a pair (5.5, 5.8)
> we get a pair (6.0, 5.4)
> we get a pair (6.0, 6.7)
> we get a pair (6.3, 5.6)
> we get a pair (5.5, 5.5)
> we get a pair (6.1, 5.8)
> we get a pair (5.0, 5.6)
> we get a pair (5.7, 5.7)
> we get a pair (6.2, 5.1)
> we get a pair (5.7, 6.3)
> we get a pair (5.8, 7.1)
> we get a pair (6.3, 6.5)
> we get a pair (7.6, 4.9)
> we get a pair (7.3, 6.7)
> we get a pair (7.2, 6.5)
> we get a pair (6.4, 6.8)
> we get a pair (5.7, 5.8)
> we get a pair (6.4, 6.5)
> we get a pair (7.7, 7.7)
> we get a pair (6.0, 6.9)
> we get a pair (5.6, 7.7)
> we get a pair (6.3, 6.7)
> we get a pair (7.2, 6.2)
> we get a pair (6.1, 6.4)
> we get a pair (7.2, 7.4)
> we get a pair (7.9, 6.4)
> we get a pair (6.3, 6.1)
> we get a pair (7.7, 6.3)
> we get a pair (6.4, 6.0)
> we get a pair (6.9, 6.7)
> we get a pair (6.9, 5.8)
> we get a pair (6.8, 6.7)
> we get a pair (6.7, 6.3)
> we get a pair (6.5, 6.2)
> we need to close stream java.io.DataInputStream@507affd3 in thread 127
> we need to close stream java.io.DataInputStream@507affd3 in thread 127
> {code}
> We can see from the end of the log that the data stream is closed twice.
> The simplest way to avoid the error is using "cache" to cut off the lineage
> as shown below. However, sometimes we do not want to cache the data.
> {code:title=work-around-zip.scala|theme=FadeToGrey|linenumbers=true|language=scala|firstline=0001|collapse=false}
> val rdd = ...
> rdd.cache()
> val rdd2 = rdd.map(x => x)
> rdd.zip(rdd2).count()
> {code}
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