Inserts per-atom mean-A reduction inside the per-branch outer loop:
Q[a, z] = V[z] + (A[a, z] - mean_a A[*, z])
The post-centering atom-level identifiability holds: Σ_a A_centered[a, z] = 0
for every (sample, branch, atom).
Per Wang et al. 2016 Dueling Networks: mean-zero is smoother and more
stable than max-zero. Atom-level subtraction (not expectation-level)
preserves distributional shape per action.
Sample-local register reduction; no atomicAdd, no shared memory, no
cross-thread sync. NUM_ATOMS_MAX=128 mirrors existing THOMPSON_MAX_ATOMS;
device __trap() on overflow.
⚠ INTERIM STATE: c51_loss_kernel + c51_grad_kernel + mag_concat_qdir
still read RAW (un-centered) advantage logits. Phase 1 Tasks 1.3-1.5
migrate them in lockstep within this branch BEFORE any L40S dispatch.
A partially-migrated state is forbidden per feedback_no_partial_refactor.
Plan: docs/superpowers/plans/2026-05-08-sp17-dueling-q-network.md
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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