[ARROW-9904] [C++] Unroll the loop manually for CountSetBits

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.0.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/25937
• Assignee: Frank Du
• Reporter: Frank Du
• Created: 03/Sep/20 02:08
• Updated: 11/Jan/23 08:09
• Resolved: 07/Sep/20 14:47

Description

The tight loop below can get better performance if unroll manually to indicate the compiler generating better parallel instructions.

for (auto iter = u64_data; iter < end; ++iter)

{ count += BitUtil::PopCount(*iter); }

Issue Links

• links to: GitHub Pull Request #8103