Single kernel per group reads (params, grads, adam_m, adam_v) once and
fuses 5 passes (4 for non-trunk):
Pass A: WEIGHT_BOUND[group] = p99(|params|) via sp4_histogram_p99
Pass B: ADAM_M_BOUND[group] = p99(|adam_m|) via sp4_histogram_p99
Pass C: ADAM_V_BOUND[group] = p99(|adam_v|) via sp4_histogram_p99
Pass D: WD_RATE[group] = |Σ w·g| / max(Σ w², ε_div); side: mean|g|, mean|w|
Pass E (group 0 only): L1_LAMBDA[trunk] via gradient-direction entropy
deficit × (mean|g|/mean|w|) magnitude scale
Launcher loops over 8 groups (DQN trunk/value/branches, IQN, IQL hi/lo,
attn, curiosity), one launch per group. Phase 2 applies Pearls A+D to
each of the 4-5 outputs per group via host-side pearls_ad_update.
Producer-scratch slots 5..38 reserved for this task's 33 outputs:
[5..13)=WEIGHT, [13..21)=ADAM_M, [21..29)=ADAM_V, [29..37)=WD_RATE, 37=L1.
Three of eight groups wired (DQN trunk/value/branches); five aux groups
(IQN, IQL hi/lo, attn, curiosity) skip silently because their backing
trainers live on FusedTrainingCtx, not GpuDqnTrainer. Wiring those
requires either threading buffer pointers through the launcher signature
or hoisting the launcher onto FusedTrainingCtx — both follow-up changes
scoped beyond Task A7. Documented in launcher + param_group_buffers
docstrings.
Per-group GPU tests verify outputs within 5% rel_err (p99 quantization)
or 2% rel_err (analytical formulas). Local RTX 3050 Ti: max WEIGHT
rel_err=0.589%, max ADAM_M=0.589%, max ADAM_V=0.554%, max WD_RATE=0.001%
across all 8 group shapes; group 0 L1 within tolerance.
Pearl B 4× memory-bandwidth reduction vs naive 4 separate per-group
producer kernels: each buffer read once for all 4-5 outputs.
No consumer wired yet — Adam kernels still take hardcoded weight_decay
+ weight_clamp_max_abs config args. Behavior unchanged.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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