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From "Matthias Boehm (JIRA)" <j...@apache.org>
Subject [jira] [Created] (SYSTEMML-1570) Remove fused sel+ operator
Date Mon, 01 May 2017 01:53:04 GMT
Matthias Boehm created SYSTEMML-1570:
----------------------------------------

             Summary: Remove fused sel+ operator
                 Key: SYSTEMML-1570
                 URL: https://issues.apache.org/jira/browse/SYSTEMML-1570
             Project: SystemML
          Issue Type: Task
            Reporter: Matthias Boehm
             Fix For: SystemML 1.0


The fused operator sel+ (select positive values) is applied for patterns like (X>0)*X and
max(X,0) in order to eliminate unnecessary intermediates. It stems from a time when max was
sparse-unsafe and hence inefficient over sparse data. However, meanwhile we mark scalar operators
as conditionally sparse-safe depending on the given scalar constant c, which applies for max
if c<=0. Hence, this sel+ operator is meanwhile completely useless and should be removed.

Furthermore, we should also generalize the rewrites to rewrite the selection of negative values
(X<0)*X to min(X,0)



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