Action enum extended:
a9 = HalfFlatLong (close ⌈|pos|/2⌉ of long position, no-op if not long)
a10 = HalfFlatShort (close ⌈|pos|/2⌉ of short position, no-op if not short)
`actions_to_market_targets.cu` extended with a9/a10 handlers:
HalfFlatLong (pos > 0): side=1 sell, size=max(1, (position_lots+1)/2)
HalfFlatShort (pos < 0): side=0 buy, size=max(1, (|position_lots|+1)/2)
Round-up division ensures min 1 lot closes — single-lot positions
fully close on HalfFlat (the half rounds up to 1).
N_ACTIONS=9 → 11 propagated to all 10 .cu kernels:
argmax_expected_q, bellman_target_projection, dqn_distributional_q,
log_pi_at_action, ppo_clipped_surrogate, rl_action_kernel,
rl_entropy_coef_controller, rl_pi_action_kernel, rl_q_pi_agree_b,
rl_q_pi_distill_grad
Rust-side N_ACTIONS const bumped to 11 in src/rl/common.rs.
CLI alpha_rl_train.rs action_hist + windowed_act_hist refactored
to reference `N_ACTIONS` const instead of literal 11. Caught DURING
this commit's dogfood: an intermediate state had `[0u32; 11]` but
left `(0..9).contains(&a)` unchanged — HalfFlat samples silently
dropped (a9/a10 showed 0% in diag despite P_MIN=0.02 floor
guaranteeing 2% each). Fix uses N_ACTIONS const everywhere; new
pearl `feedback_use_consts_not_literals_for_structural_dims`
codifies the meta-pattern (Rust code mirroring kernel structural
dims must reference the const, NEVER duplicate the literal —
audit-isv only scans .cu files, this class of bug is currently
unaudited in .rs).
Audits PASS:
audit-isv: all kernel #defines allowlisted (BOOK_LEVELS,
ACTION_*, structural dims)
audit-wiring: all 4 actions in manifest (TrailTighten, TrailLoosen,
HalfFlatLong, HalfFlatShort) have consumers
Local 1k-step smoke (RTX 3050 Ti, 13.5s):
* Exit 0, 0 NaN/inf, 16000/16000 samples accounted for
* Action distribution: all 11 used in 7-11% range
* HalfFL=7.99%, HalfFS=7.51% — π samples them under multinomial
* Trail=19.34% — agent continues to value trail-stop actions
Trail-stop check (rl_trail_stop_check.cu) currently still routes
force-close through a3/a4 (FlatFromLong/Short) rather than per-unit
partial-flat via a9/a10. That routing upgrade is SP20 P5b follow-up
work — it requires the per-unit close_unit_index buffer wiring per
spec §3 P5. Adding a9/a10 to the action space is the foundational
prerequisite; consumer kernel uses come with P5b.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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