# H100 Epoch Optimization Phase 4: Init Elimination

> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.

**Goal:** Eliminate the 73ms/epoch init overhead by keeping GPU data resident across epochs, reducing total epoch time from 153ms to ~80ms.

**Architecture:** Remove the per-epoch GPU data freeing that forces re-upload. The training data within a walk-forward window is immutable — uploading it once and keeping it GPU-resident eliminates the largest remaining bottleneck.

**Tech Stack:** Rust, cudarc 0.19

---

### Task 1: Stop freeing GPU data between epochs

**Files:**
- Modify: `crates/ml/src/trainers/dqn/trainer/training_loop.rs:109-116`

- [ ] **Step 1: Remove the GPU data freeing block**

Delete lines 109-116 in `training_loop.rs`:
```rust
// Free DqnGpuData when GPU experience collector is active
if gpu_experiences_collected && self.gpu_data.is_some() {
    info!("GPU experience collector active — releasing DqnGpuData to reclaim VRAM");
    self.gpu_data = None;
    if let Some(pool) = self.buffer_pool.take() {
        drop(pool);
    }
}
```

The training data is immutable within a walk-forward window. The experience collector has its own buffer copies. Freeing and re-uploading wastes 73ms/epoch.

- [ ] **Step 2: Verify compilation + tests**

Run: `SQLX_OFFLINE=true cargo check -p ml`
Run: `SQLX_OFFLINE=true cargo test -p ml --lib`

- [ ] **Step 3: GPU smoke test**

Run: `SQLX_OFFLINE=true FOXHUNT_TEST_DATA=test_data/futures-baseline cargo test -p ml --lib -- test_train_step_produces_finite_metrics --ignored --test-threads=1`

- [ ] **Step 4: Profile**

Run: `SQLX_OFFLINE=true cargo run --release --example train_baseline_rl -p ml -- --model dqn --data-dir test_data/futures-baseline --symbol ES.FUT --epochs 5 --max-steps-per-epoch 50 --batch-size 64 --train-months 3 --val-months 1 --test-months 1 --step-months 3 2>&1 | grep "phase breakdown"`

Expected: init < 5ms (down from 73ms), total epoch < 100ms.

- [ ] **Step 5: Commit**

```bash
git add crates/ml/src/trainers/dqn/trainer/training_loop.rs
git commit -m "perf: keep GPU training data resident across epochs (eliminate 73ms/epoch re-upload)"
```
