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https://issues.apache.org/jira/browse/FLINK-4586?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15582283#comment-15582283
]
ASF GitHub Bot commented on FLINK-4586:
---------------------------------------
Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/2639#discussion_r83643344
--- Diff:
flink-core/src/main/java/org/apache/flink/api/common/accumulators/AverageAccumulator.java
---
@@ -28,51 +28,52 @@
public class AverageAccumulator implements SimpleAccumulator<Double> {
private static final long serialVersionUID = 3672555084179165255L;
-
- private double localValue;
+
private long count;
+ private double sum;
+
@Override
public void add(Double value) {
this.count++;
- this.localValue += value;
+ this.sum += value;
}
public void add(double value) {
this.count++;
- this.localValue += value;
+ this.sum += value;
}
public void add(long value) {
this.count++;
- this.localValue += value;
+ this.sum += value;
}
public void add(int value) {
this.count++;
- this.localValue += value;
+ this.sum += value;
}
@Override
public Double getLocalValue() {
if (this.count == 0) {
return 0.0;
}
- return this.localValue / (double)this.count;
+ return this.sum / this.count;
}
@Override
public void resetLocal() {
this.count = 0;
- this.localValue = 0;
+ this.sum = 0;
}
@Override
public void merge(Accumulator<Double, Double> other) {
if (other instanceof AverageAccumulator) {
- AverageAccumulator temp = (AverageAccumulator)other;
- this.count += temp.count;
- this.localValue += other.getLocalValue();
--- End diff --
I guess this was the buggy line?
> NumberSequenceIterator and Accumulator threading issue
> ------------------------------------------------------
>
> Key: FLINK-4586
> URL: https://issues.apache.org/jira/browse/FLINK-4586
> Project: Flink
> Issue Type: Bug
> Components: DataSet API
> Affects Versions: 1.1.2
> Reporter: Johannes
> Assignee: Greg Hogan
> Priority: Minor
> Fix For: 1.2.0, 1.1.4
>
> Attachments: FLINK4586Test.scala
>
>
> There is a strange problem when using the NumberSequenceIterator in
> combination with an AverageAccumulator.
> It seems like the individual accumulators are reinitialized and overwrite
> parts of intermediate solutions.
> The following scala snippit exemplifies the problem.
> Instead of printing the correct average, the result should be {{50.5}} but is
> something completely different, like {{8.08}}, dependent on the number of
> cores used.
> If the parallelism is set to {{1}} the result is correct, which indicates a
> likely threading problem.
> The problem occurs using the java and scala API.
> {code}
> env
> .fromParallelCollection(new NumberSequenceIterator(1, 100))
> .map(new RichMapFunction[Long, Long] {
> var a : AverageAccumulator = _
> override def map(value: Long): Long = {
> a.add(value)
> value
> }
> override def open(parameters: Configuration): Unit = {
> a = new AverageAccumulator
> getRuntimeContext.addAccumulator("test", a)
> }
> })
> .reduce((a, b) => a + b)
> .print()
> val lastJobExecutionResult: JobExecutionResult = env.getLastJobExecutionResult
> println(lastJobExecutionResult.getAccumulatorResult("test"))
> {code}
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