Quanlong Huang created ORC-1137:
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Summary: [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
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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