[ARROW-5639] [Java] Remove floating point computation from getOffsetBufferValueCapacity

• Type: Improvement
• Status: Resolved
• Priority: Trivial
• Resolution: Fixed
• Fix Version/s: 0.14.0
• Component/s: Java
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/22075
• Assignee: Liya Fan
• Reporter: Liya Fan
• Created: 18/Jun/19 12:31
• Updated: 11/Jan/23 07:41
• Resolved: 20/Jun/19 06:44

Description

Some getOffsetBufferValueCapacity methods uses floating point computation to calculate the capacity, which is not necessary.

(int) ((offsetBuffer.capacity() * 1.0) / OFFSET_WIDTH);

It is interesting to note that JIT cannot optimize away the floating point computations:

So this has performance penalty:
Before:
VariableWidthVectorBenchmarks.getValueCapacity avgt 5 6.570 ± 0.004 ns/op

After:
VariableWidthVectorBenchmarks.getValueCapacity avgt 5 5.787 ± 0.575 ns/op

Issue Links

• links to: GitHub Pull Request #4602