jgrusewski 13bf277cd6 feat(rl): Phase 4.1 — DuelingQHead loss + Bellman target + decompose backward
Implements §4.2/4.3/4.4 + §5 of Phase 4 spec.

Three new CUDA kernels:

1. rl_dueling_q_bellman_target.cu — argmax over target composed_Q at
   s_{t+1}, build target_value = r + γ^n × (1-done) × max_Q. Grid
   (B,1,1), block (N_ACTIONS,1,1). Reads γ via per-sample n_step_gammas
   passed by trainer (matches PER convention).

2. rl_dueling_q_loss_and_grad.cu — scalar Huber loss on
   (target − online_composed_Q[taken]). Emits per-batch loss and
   grad_composed (only taken action has nonzero gradient — this is
   single-Q scalar regression, not distributional CE). Grid (B,1,1),
   block (N_ACTIONS,1,1). Threads write zero into non-taken cells.

3. rl_dueling_q_decompose_and_bwd.cu — decompose grad_composed →
   grad_V + grad_A via mean-subtraction Jacobian:
     grad_V[b]    = Σ_a grad_composed[b, a] = grad_composed[b, a_taken]
     grad_A[b, a] = grad_composed[b, a] − (1/N) × grad_V[b]
   Then computes per-batch weight gradients via outer product with h_t:
     grad_w_v_pb[b, c]    = grad_V[b] × h_t[b, c]
     grad_b_v_pb[b]       = grad_V[b]
     grad_w_a_pb[b, c, a] = grad_A[b, a] × h_t[b, c]
     grad_b_a_pb[b, a]    = grad_A[b, a]
   Grid (B,1,1), block (HIDDEN_DIM,1,1). Thread 0 also writes biases.

DuelingQHead Rust API (3 new methods):
  - build_bellman_target(target_composed_q, r, dones, n_step_gammas, B, out)
  - compute_loss_and_grad(online_composed_q, target_value, actions, B,
                          loss_pb, grad_composed_out)
  - decompose_and_backward_to_weights(h_t, grad_composed, actions, B,
                                      grad_w_v_pb, grad_b_v_pb,
                                      grad_w_a_pb, grad_b_a_pb)

Caller (trainer) is responsible for reduce_axis0 of per-batch grads
→ final weight gradients [HIDDEN_DIM], [1], [HIDDEN_DIM × N_ACTIONS],
[N_ACTIONS]. Will be wired in Phase 4.2.

Soft-update of target weights still TODO — recommend reusing
dqn_target_soft_update kernel pattern in Phase 4.2.

Validated:
  - cargo build --release clean
  - integrated_trainer_smoke (1 step) passes

Per pearl_complement_internal_loss_vs_external_consumers: this loss
path is fully internal to DuelingQHead. No downstream consumer ever
sees composed_Q or grad_composed. The four prior session failure
modes are structurally impossible.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
2026-05-30 08:33:18 +02:00

Foxhunt

Production HFT trading system in Rust.

Architecture

The workspace contains 32 crates organized as follows:

Core Libraries (16)

Crate Purpose
trading_engine Order processing, FIX 4.4, IB TWS, SIMD, RDTSC timing
risk VaR, Kelly, circuit breakers, kill switches, compliance
risk-data Risk data types and shared structures
trading-data Trading data types
ml DQN Rainbow, PPO, TFT, Mamba2, ensemble inference
ml-data ML data types and feature definitions
data Market data ingestion and storage
backtesting Replay engine, strategy tester
adaptive-strategy Ensemble execution, microstructure analysis
common Shared types, resilience, error handling
storage S3 and local model storage
model_loader Model serialization and loading
market-data Market data feed handlers
database PostgreSQL access layer (SQLx)
config Configuration management
tli CLI commands and tooling

Services (8)

Service Purpose
backtesting_service gRPC backtesting service
broker_gateway_service FIX routing, broker connectivity
trading_service Core trading operations
ml_training_service Model training orchestration
data_acquisition_service Market data acquisition
trading_agent_service Autonomous trading agents
api_gateway gRPC API gateway with auth
web-gateway Axum REST + WebSocket gateway

Frontend

web-dashboard/ -- React 19 + TypeScript + Vite + TradingView charts.

Building

# Check compilation (no PostgreSQL required)
SQLX_OFFLINE=true cargo check --workspace

# Run tests for a specific crate
SQLX_OFFLINE=true cargo test -p <crate> --lib

# Clippy
SQLX_OFFLINE=true cargo clippy --workspace

ML Models

Four production model architectures on Candle v0.9.1 with CUDA:

  • DQN Rainbow -- Deep Q-Network with prioritized replay, dueling heads, noisy nets
  • PPO -- Proximal Policy Optimization with GAE and LSTM policies
  • TFT -- Temporal Fusion Transformer for multi-horizon forecasting
  • Mamba2 -- State space model for sequence prediction

Each model has a standalone trainer and a UnifiedTrainable adapter for the hyperopt pipeline.

Infrastructure

  • Git: Gitea at git.fxhnt.ai (Tailscale-only), Scaleway DEV1-S
  • Observability: OpenTelemetry OTLP (env OTEL_EXPORTER_OTLP_ENDPOINT)
  • Database: PostgreSQL with SQLx offline mode for CI

License

Proprietary. All rights reserved.

Description
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