Liya Fan created ARROW-7098:
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Summary: [Java] Improve the performance of comparing two memory
blocks
Key: ARROW-7098
URL: https://issues.apache.org/jira/browse/ARROW-7098
Project: Apache Arrow
Issue Type: Improvement
Components: Java
Reporter: Liya Fan
Assignee: Liya Fan
We often use the 8-4-1 paradigm to compare two blocks of memory:
1. First compare by 8-byte blocks in a loop
2. Then compare by 4-byte blocks in a loop
3. Last compare by 1-byte blocks in a loop
It can be proved that the second loop runs at most once. So we can replace the
loop with a if statement, which will save us a comparison and two jump
operations.
According to the discussion in
https://github.com/apache/arrow/pull/5508#discussion_r343973982, loop can be
expensive.
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