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From "Matthias Boehm (JIRA)" <j...@apache.org>
Subject [jira] [Created] (SYSTEMML-2173) Upper bound nnz propagation over spark instructions
Date Wed, 07 Mar 2018 20:52:00 GMT
Matthias Boehm created SYSTEMML-2173:
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             Summary: Upper bound nnz propagation over spark instructions
                 Key: SYSTEMML-2173
                 URL: https://issues.apache.org/jira/browse/SYSTEMML-2173
             Project: SystemML
          Issue Type: Bug
            Reporter: Matthias Boehm


Due to lazy evaluation, many spark instructions propagate nnz only if they can be exactly
inferred from the input meta data. Especially for ultra-sparse matrices this poses a challenge
because intermediates quickly reach a state where they're assumed to be dense. However, many
operations such as right indexing allow to upper bound the nnz with the nnz in the input,
which can be propagated and exploited in subsequent instructions.



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