The speedup column in a result table compares gems against torch, not one build
against another, so an A/B needs the two runs paired by shape. batch_summary
gains an --ab mode that indexes both run.logs by operator, dtype and size
detail, computes before/after per pair, and prints the per-shape rows plus the
range. Only rows that succeeded on both sides with a positive latency count, so
an incomplete pairing cannot masquerade as a complete range. When either side
carries a BENCHMARK_DIRECT_NO_CUDAGRAPH marker the range is annotated, because
a fallback row was timed under a different regime than a captured one.
ab_rlc_test.sh drives the pairing for the FlagTree RemoveLayoutConversions
switch the way ab_fold_test.sh does for the FlagGems one: per operator, run with
the enhancement off while recording autotune configs, then replay those configs
with it on, so the two sides differ by that switch alone. Each operator
therefore leaves exactly two run.log files, and the summary of each pair is
printed as it completes.
Checked on an S5000 against gelu_backward over five shapes: both sides captured
with no fallback, five rows paired, range -0.43% to +0.09%.
