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From "LI Guobao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SYSTEMML-2197) Multi-threaded broadcast creation
Date Fri, 06 Apr 2018 18:14:00 GMT

    [ https://issues.apache.org/jira/browse/SYSTEMML-2197?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16428709#comment-16428709
] 

LI Guobao commented on SYSTEMML-2197:
-------------------------------------

Thanks, I successfully launched this test and got 4 failed tests(testDenseDenseMapmmMR, testDenseSparseMapmmMR,
testSparseDenseMapmmMR, testSparseSparseMapmmMR). And it seems to concern the MR backend.
When reswitching to the master branch, I got the same result. So is it a detected bug? Could
I ignore it? Thanks for the response. Here is the stack information:
{code:java}
18/04/06 19:38:48 ERROR api.DMLScript: Failed to execute DML script.
org.apache.sysml.runtime.DMLRuntimeException: org.apache.sysml.runtime.DMLRuntimeException:
ERROR: Runtime error in program block generated from statement block between lines 23 and
27 -- Error evaluating instruction: jobtype = GMR 
input labels = [_mVar13, _mVar14] 
recReader inst = 
rand inst = 
mapper inst = MR°mapmm°0·MATRIX·DOUBLE°1·MATRIX·DOUBLE°2·MATRIX·DOUBLE°RIGHT°false

shuffle inst = 
agg inst = MR°ak+°2·MATRIX·DOUBLE°3·MATRIX·DOUBLE°true°NONE 
other inst = 
output labels = [pVar15] 
result indices = ,3 
num reducers = 10 
replication = 1 

at org.apache.sysml.runtime.controlprogram.Program.execute(Program.java:123)
at org.apache.sysml.api.ScriptExecutorUtils.executeRuntimeProgram(ScriptExecutorUtils.java:97)
at org.apache.sysml.api.DMLScript.execute(DMLScript.java:744)
at org.apache.sysml.api.DMLScript.executeScript(DMLScript.java:515)
at org.apache.sysml.api.DMLScript.main(DMLScript.java:246)
at org.apache.sysml.test.integration.AutomatedTestBase.runTest(AutomatedTestBase.java:1214)
at org.apache.sysml.test.integration.functions.binary.matrix_full_other.FullDistributedMatrixMultiplicationTest.runDistributedMatrixMatrixMultiplicationTest(FullDistributedMatrixMultiplicationTest.java:276)
at org.apache.sysml.test.integration.functions.binary.matrix_full_other.FullDistributedMatrixMultiplicationTest.testSparseSparseMapmmMR(FullDistributedMatrixMultiplicationTest.java:101){code}

> Multi-threaded broadcast creation
> ---------------------------------
>
>                 Key: SYSTEMML-2197
>                 URL: https://issues.apache.org/jira/browse/SYSTEMML-2197
>             Project: SystemML
>          Issue Type: Task
>            Reporter: Matthias Boehm
>            Assignee: LI Guobao
>            Priority: Major
>
> All spark instructions that broadcast one of the input operands, rely on a shared primitive
{{sec.getBroadcastForVariable(var)}} for creating partitioned broadcasts, which are wrapper
objects around potentially many broadcast variables to overcome Spark 2GB limitation for compressed
broadcasts. Each individual broadcast blocks the matrix into squared blocks for direct access
without unnecessary copy per task. So far this broadcast creation is single-threaded. 
> This task aims to parallelize the blocking of the given in-memory matrix into squared
blocks (https://github.com/apache/systemml/blob/master/src/main/java/org/apache/sysml/runtime/instructions/spark/data/PartitionedBlock.java#L82)
as well as the subsequent partition creation and actual broadcasting (https://github.com/apache/systemml/blob/master/src/main/java/org/apache/sysml/runtime/controlprogram/context/SparkExecutionContext.java#L548).

> For consistency and in order to avoid excessive over-provisioning, this multi-threading
should use the common internal thread pool or parallel java streams, which similarly calls
the shared {{ForkJoinPool.commonPool}}. An example is the multi-threaded parallelization of
RDDs which similarly blocks a given matrix into its squared blocks (see https://github.com/apache/systemml/blob/master/src/main/java/org/apache/sysml/runtime/controlprogram/context/SparkExecutionContext.java#L679).



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