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From "Matthias Boehm (JIRA)" <>
Subject [jira] [Commented] (SYSTEMML-1570) Remove fused sel+ operator
Date Wed, 24 May 2017 06:45:04 GMT


Matthias Boehm commented on SYSTEMML-1570:

thanks [~nakul02] - it's not urgent but I would like to remove this sel+(X) operator in favor
of max(X,0) rather sooner than later in order to avoid that people implement additional rewrites
or custom conditions on top of it.

> Remove fused sel+ operator
> --------------------------
>                 Key: SYSTEMML-1570
>                 URL:
>             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
> 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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