[Bug libstdc++/83938] New: Speed up inplace_merge() algorithm & fix inefficient logic

[john.chang at samba dot tv]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83938

            Bug ID: 83938
           Summary: Speed up inplace_merge() algorithm & fix inefficient
                    logic
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: john.chang at samba dot tv
  Target Milestone: ---

In this report we review the inplace merge algorithm of current GCC libstdc++.

We survey a potential issue about downgrade of performance when merging two
sorted vectors given limited buffer.

The experiment result shows at most a 49.18% gain in execution time or reduce
50 % in memory usage.

Please estimate to enhance it.

Attached is the report in detail.

Thanks.