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 <[email protected]> Gerrit-Reviewer: Attila Jeges <[email protected]> Gerrit-Reviewer: Impala Public Jenkins Gerrit-Reviewer: Jim Apple <[email protected]> Gerrit-Reviewer: Kim Jin Chul <[email protected]> Gerrit-Reviewer: Michael Ho <[email protected]> Gerrit-Comment-Date: Fri, 17 Nov 2017 03:13:49 +0000 Gerrit-HasComments: Yes
