Taras Bobrovytsky has posted comments on this change. Change subject: IMPALA-4939, IMPALA-4939: Decimal V2 multiplication ......................................................................
Patch Set 4: (1 comment) http://gerrit.cloudera.org:8080/#/c/7438/4//COMMIT_MSG Commit Message: Line 75: DECIMAL_V2 disabled: 2.65s > This is scary and I don't think we should consider merging this until it's It takes time to convert a number from 128 bits to 256 bits. Also, Boost does something like 4 128 bit multiplications internally in the 256 bit multiplication function (so it makes sense for it to be at least 4x slower). I think the 256 bit multiplication function is also not optimized for the worst case (where the result actually needs more than 128 bits). Also, it takes time to convert 2 numbers to 256 bit numbers and then convert 1 number back. I don't think it's that surprising that it's much slower. 256 bit multiplication is slow and is not implemented in hardware like others. Remember, this benchmark is the absolute worst case scenario, where we do a 256 bit multiplication for every row. -- 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 <[email protected]> Gerrit-Reviewer: Dan Hecht <[email protected]> Gerrit-Reviewer: Michael Ho <[email protected]> Gerrit-Reviewer: Taras Bobrovytsky <[email protected]> Gerrit-Reviewer: Tim Armstrong <[email protected]> Gerrit-Reviewer: Zach Amsden <[email protected]> Gerrit-HasComments: Yes
