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https://issues.apache.org/jira/browse/MAPREDUCE-6724?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15375783#comment-15375783
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Daniel Templeton commented on MAPREDUCE-6724:
---------------------------------------------

Thanks for the patch, [~haibochen]!  A couple comments:

{code}
    final long totalReduceMem = 8L * 1024 * 1024 * 1024;
    final float shuffleInputBuf = 1.0f;
    final float reduceInputBuf = 1.0f;
    final MergeManagerImpl<Text, Text> mgr = createMergeManager(
        totalReduceMem, shuffleInputBuf, 0.95f, reduceInputBuf);
{code}

It would be better to be consistent in the parameters.  Everything is a 
variable except for the shuffle memory limit.

{code}
    final long totalReduceMem = 10000000000000000L;
    final float shuffleInputBuf = 1.0f;
    final float shuffleMemLimit =
        singleShuffleLimitConfiged / (float) totalReduceMem;
    final MergeManagerImpl<Text, Text> mgr = createMergeManager(
        totalReduceMem, shuffleInputBuf, shuffleMemLimit, 1.0f);
{code}

Same comment here, except with reducer input buffer.

> Unsafe conversion from long to int in MergeManagerImpl.unconditionalReserve()
> -----------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-6724
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6724
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv2
>            Reporter: Haibo Chen
>            Assignee: Haibo Chen
>         Attachments: mapreduce6724.001.patch, mapreduce6724.002.patch, 
> mapreduce6724.003.patch
>
>
> When shuffle is done in memory, MergeManagerImpl converts the requested size 
> to an int to allocate an instance of InMemoryMapOutput. This results in an 
> overflow if the requested size is bigger than Integer.MAX_VALUE and 
> eventually causes the reducer to fail.



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