SP6 sub-project 1 (Pearl 2): converts the 4 SAXPY launchers from a single
scalar budget (mean of 4 ISV branch slots) to per-branch differentiated
scaling via the correction-factor pattern.
Problem: SP5 Layer B read ISV[190..210) per-branch budget slots but
collapsed them to a scalar via sum/4.0, then passed the single scalar to
apply_c51_budget_scale / apply_cql_saxpy / apply_iqn_trunk_gradient.
Branch HEAD parameters received the same budget as trunk, defeating
per-branch differentiation.
Fix: compute_adaptive_budgets() now returns ([f32;4], [f32;4], [f32;4],
[f32;4], f32, f32, f32, f32) — four per-branch arrays + four trunk-mean
scalars. The trunk mean (D3 decision) is used for the full-buffer trunk/value
SAXPY call (preserving SP5 Layer B behavior for shared params). Branch HEAD
parameter slices receive a correction sub-launch:
correction = branch_budget[b] / trunk_mean (skip if |correction-1| <= 1e-6)
After both launches, branch HEAD slice is effectively scaled by
branch_budget[b], trunk/value is scaled by trunk_mean. No double-scaling.
New helpers added to GpuDqnTrainer:
apply_c51_budget_scale_branch(branch_idx, correction): scale_f32_ungraphed
on branch-slice [f32 elements], offset via padded_byte_offset.
apply_cql_saxpy_branch(branch_idx, correction): saxpy_f32_aux on
branch-slice of both grad_buf and cql_grad_scratch.
IQN trunk gradient: uses iqn_trunk (mean of 4 branch IQN budgets) — IQN
backward flows through trunk only; per-branch IQN routing is beyond SP6 scope.
HEALTH_DIAG: three new per-epoch info! lines emit per-branch c51/iqn/cql
budget arrays (dir/mag/ord/urg) after the intent_dist line.
State: per-branch budget arrays cached on GpuDqnTrainer
(last_*_budget_per_branch: [f32;4]) and on DqnTrainer
(last_*_budget_per_branch: Option<[f32;4]>) for diagnostics.
docs/isv-slots.md: updated Pearl 2 slot rows to reflect SP6 consumer wiring.
Verification: cargo check + release build clean (13 warnings, pre-existing).
13 sp5+sp4+state_reset_registry lib tests pass. sp5_producer_unit_tests
--no-run clean. Sanity grep for old sum/4.0 averaging pattern: empty.
Files changed (6): gpu_dqn_trainer.rs, fused_training.rs, constructor.rs,
mod.rs, training_loop.rs, docs/isv-slots.md. No Pearl 3 or Pearl 5 files touched.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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