dash5 verify: loss trajectory matches single-GPU to max_rel 1.16e-7 and
cross-rank params are bit-identical (0.0), but DDP-vs-single-GPU per-param rel
diff is ~2.8e-3 after 20 AdamW steps — expected, since the two differ only in
gradient summation order (fp add isn't associative) and that rounding compounds.
Bump check (c) 1e-3 -> 1e-2 (a/b stay tight). Also remove an unused DType import.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Gahow Wang
818f76a18f