impala-reviews mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Michael Ho (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-5754: Improve randomness of rand()/random()
Date Fri, 17 Nov 2017 03:13:49 GMT
Michael Ho has posted comments on this change. ( http://gerrit.cloudera.org:8080/8355 )

Change subject: IMPALA-5754: Improve randomness of rand()/random()
......................................................................


Patch Set 14:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/8355/14/be/src/exprs/math-functions-ir.cc
File be/src/exprs/math-functions-ir.cc:

http://gerrit.cloudera.org:8080/#/c/8355/14/be/src/exprs/math-functions-ir.cc@165
PS14, Line 165: mt19937* generator = ctx->Allocate<mt19937>();
> I think about a worst case. For example,
That does increase the chance of query failure.

I am not too familiar with the usage of mt19937 but have you considered the the option to
stack allocate the generator in MathFunctions::Rand() instead as long as we keep track the
seed value like the old code ? Or did you try it and found it too slow or somehow undesirable
?



-- 
To view, visit http://gerrit.cloudera.org:8080/8355
To unsubscribe, visit http://gerrit.cloudera.org:8080/settings

Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Idafdd5fe7502ff242c76a91a815c565146108684
Gerrit-Change-Number: 8355
Gerrit-PatchSet: 14
Gerrit-Owner: Kim Jin Chul <jinchul@gmail.com>
Gerrit-Reviewer: Attila Jeges <attilaj@cloudera.com>
Gerrit-Reviewer: Impala Public Jenkins
Gerrit-Reviewer: Jim Apple <jbapple-impala@apache.org>
Gerrit-Reviewer: Kim Jin Chul <jinchul@gmail.com>
Gerrit-Reviewer: Michael Ho <kwho@cloudera.com>
Gerrit-Comment-Date: Fri, 17 Nov 2017 03:13:49 +0000
Gerrit-HasComments: Yes

Mime
  • Unnamed multipart/alternative (inline, 8-Bit, 0 bytes)
View raw message