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https://issues.apache.org/jira/browse/TEZ-3126?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15155030#comment-15155030
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Bikas Saha commented on TEZ-3126:
---------------------------------
Sure.
When we have per partition sizes then we can remove these restriction and just
group partitions till we hit the per task limit and then move on to the next
task. Repeat till all partitions have been merged. [~rajesh.balamohan] do you
think the current stats have enough fidelity to make that happen?
> Auto-Reduce Parallelism: Vertex not re-configured when reduced by less than
> half.
> ---------------------------------------------------------------------------------
>
> Key: TEZ-3126
> URL: https://issues.apache.org/jira/browse/TEZ-3126
> Project: Apache Tez
> Issue Type: Bug
> Reporter: Jonathan Eagles
> Assignee: Jonathan Eagles
> Priority: Critical
> Attachments: TEZ-3126.1.patch
>
>
> For example, when reducing parallelism from 36 to 22. The basePartitionRange
> will be 1 and will not re-configure the vertex.
> {code:java|title=ShuffleVertexManager#determineParallelismAndApply|borderStyle=dashed|bgColor=lightgrey}
> int desiredTaskParallelism =
> (int)(
> (expectedTotalSourceTasksOutputSize+desiredTaskInputDataSize-1)/
> desiredTaskInputDataSize);
> if(desiredTaskParallelism < minTaskParallelism) {
> desiredTaskParallelism = minTaskParallelism;
> }
>
> if(desiredTaskParallelism >= currentParallelism) {
> return true;
> }
>
> // most shufflers will be assigned this range
> basePartitionRange = currentParallelism/desiredTaskParallelism;
>
> if (basePartitionRange <= 1) {
> // nothing to do if range is equal 1 partition. shuffler does it by
> default
> return true;
> }
> {code}
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