Tim Armstrong has posted comments on this change. Change subject: IMPALA-4939, IMPALA-4939: Decimal V2 multiplication ......................................................................
Patch Set 4: (4 comments) http://gerrit.cloudera.org:8080/#/c/7438/4//COMMIT_MSG Commit Message: Line 7: IMPALA-4939, IMPALA-4939: Decimal V2 multiplication The same JIRA is listed twice. Line 75: DECIMAL_V2 disabled: 2.65s This is scary and I don't think we should consider merging this until it's fixed (or we have a strong reason why the regression is unavoidable and justified). Do we understand why the int256_t is so much slower? http://gerrit.cloudera.org:8080/#/c/7438/1/be/src/runtime/decimal-value.inline.h File be/src/runtime/decimal-value.inline.h: Line 301: // The following is frought with apparent difficulty, as there is only 1 bit > Added a TODO. It seems most efficient development-wise if we give this a try now while we're working on and benchmarking this code instead of leaving a TODO. This could be a big win - I know the div here is a big contributor to runtime for some queries, e.g. TPC-H Q1 http://gerrit.cloudera.org:8080/#/c/7438/1/be/src/util/bit-util.h File be/src/util/bit-util.h: Line 65: return value < 0 ? -1 : 1; > I included the benchmark result in the commit message. Does it compile to the same assembly (or better assembly) as before? If it's adding a branch, the benchmark may be misleading since the worst case would be a 50/50 mix of positive and negative types, leading to branch mispredicts. Another option is to keep the existing implementation and specialise the template for int256. -- To view, visit http://gerrit.cloudera.org:8080/7438 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-MessageType: comment Gerrit-Change-Id: I37ad6232d7953bd75c18dc86e665b2b501a1ebe1 Gerrit-PatchSet: 4 Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-Owner: Taras Bobrovytsky <tbobrovyt...@cloudera.com> Gerrit-Reviewer: Dan Hecht <dhe...@cloudera.com> Gerrit-Reviewer: Michael Ho <k...@cloudera.com> Gerrit-Reviewer: Taras Bobrovytsky <tbobrovyt...@cloudera.com> Gerrit-Reviewer: Tim Armstrong <tarmstr...@cloudera.com> Gerrit-Reviewer: Zach Amsden <zams...@cloudera.com> Gerrit-HasComments: Yes
