[jira] [Commented] (JENA-2116) Performance regression in xsd:decimal division.

["Andy Seaborne (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/JENA-2116?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17367135#comment-17367135 ] 

Andy Seaborne commented on JENA-2116:
-------------------------------------

The report is using decimal divide to achieve a "remainder" operation. This has been split into JENA-2122 to provide {{mod}} and {{idiv}}.

The decimal divide with arbitrary precision JENA-1943 uses an exception when the decimal result can not be exactly represented. This seems unavoidable.

It triggered in the report because the "divide by 7200" is not exact in XSD decimal (factor of 3).

A partial optimization to not create unnecessary lexical forms (the value result is need, the lexical form is not) can be added. This makes an approximately 20% improvement.

Otherwise the change from JENA-143 remains in-place.


> Performance regression in xsd:decimal division.
> -----------------------------------------------
>
>                 Key: JENA-2116
>                 URL: https://issues.apache.org/jira/browse/JENA-2116
>             Project: Apache Jena
>          Issue Type: Bug
>          Components: ARQ
>    Affects Versions: Jena 3.17.0, Jena 4.0.0, Jena 4.1.0
>            Reporter: Andy Seaborne
>            Assignee: Andy Seaborne
>            Priority: Major
>
> [Report from users@ : 2021-06-04|https://lists.apache.org/thread.html/ra55320e0f0f63364093d100fde3083e73065cab4bdbdcb693f8fe95c%40%3Cusers.jena.apache.org%3E]
> As a result of JENA-1943, Java BigDecimal division will cause an ArithmeticException when then is no exact decimal result. In the report, division by 3 will mean no exact answer.
> But the change in JENA-1943 (arbitray precision for exact answers) is also desirable. Simply having a quite large division precise (e.g. 100) isn't ideal because e.g. {{1/3}} returns {{0.333333333333333333333333}} (precision of 24) currently, not {{0.3333......}} length about 100.
> Also, there is an unnecessary canonicalization of a value that is only used in further calculation so the lexical form isn't needed.



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