[jira] [Assigned] (ORC-1137) [C++] Improve float/double conversion in DoubleColumnReader::next()

["Quanlong Huang (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ORC-1137?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Quanlong Huang reassigned ORC-1137:
-----------------------------------


> [C++] Improve float/double conversion in DoubleColumnReader::next()
> -------------------------------------------------------------------
>
>                 Key: ORC-1137
>                 URL: https://issues.apache.org/jira/browse/ORC-1137
>             Project: ORC
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Quanlong Huang
>            Assignee: Quanlong Huang
>            Priority: Major
>         Attachments: DoubleColumnReader.png, DoubleColumnReader_readDouble.png
>
>
> DoubleColumnReader::next() takes a portion of time when reading doubles from a tpch-lineitem ORC file. I can see the loop in readDouble is unrolled. But it still have redundant checks. We can manually unroll it to save some instructions.
> Furthermode, in little-endian machines, the layout of the DATA stream of the DOUBLE column matches the memory layout of the output array. We can use std::memcpy to copy the data directly.
>  



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