An APS5_AB run interleaves phases A and B, and every periodic report
covers the time since the previous report of its kind, so its numbers
need sorting before A and B can be compared. tools/ab_split.py reads
the [ab] lines and counts a [present], [gputime], [draw] pipelined or
[syncwait] report for a phase only when its whole span lies inside the
phase after its settled line. It prints presents per 10 s and frame
time per phase, GPU busy and idle time per frame, GPU time per present
(also per --program key and --class), committer, drain and hook-wait
times, the A and B means, and each B phase against the mean of its
neighbouring A phases, which cancels a linear drift.
AI-assisted: yes
