Adaptive Householder Gradient Subspaces / adaptive_bench.py

Mechanism confirmed, baseline not beaten

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  1import json, math, sys, time
  2from pathlib import Path
  3import numpy as np
  4import torch
  5from torch import nn
  6
  7sys.path.insert(0, "/home/maxwelhelp/all/math2nn")
  8from bench import get_dataset, make_model, evaluate, sweep_baseline, make_report
  9
 10SEEDS = tuple(range(8))
 11LR_GRID = [0.001, 0.003, 0.006]
 12# These are fixed before running: adaptive tolerance, Gaussian block, and max rank.
 13IDEA_GRID = [{"lr": lr, "rel_tol": 0.30, "block": 4, "kmax": 16} for lr in LR_GRID]
 14EPOCHS = 12
 15BATCH = 128
 16
 17
 18def adaptive_subspace(g, rel_tol=0.30, block=4, kmax=16, generator=None):
 19    """Adaptive randomized range finder for a 2-D gradient matrix.
 20
 21    QR is the numerically stable Householder implementation in torch.linalg.qr.
 22    The returned Q is explicit for this small MVP; production code would retain
 23    reflector factors and apply them implicitly.
 24    """
 25    m, n = g.shape
 26    kmax = min(int(kmax), m, n)
 27    initial = torch.sum(g * g).detach()
 28    residual = g.clone()
 29    blocks = []
 30    energy = initial
 31    while float(energy) > float(initial) * rel_tol * rel_tol and sum(q.shape[1] for q in blocks) < kmax:
 32        b = min(int(block), kmax - sum(q.shape[1] for q in blocks))
 33        omega = torch.randn((n, b), device=g.device, dtype=g.dtype, generator=generator)
 34        y = residual @ omega
 35        # Residual construction makes the new block orthogonal to prior blocks;
 36        # QR itself is Householder-stable within the block.
 37        q, _ = torch.linalg.qr(y, mode="reduced")
 38        if q.shape[1] == 0:
 39            break
 40        blocks.append(q)
 41        residual = residual - q @ (q.T @ residual)
 42        energy = torch.sum(residual * residual).detach()
 43    if not blocks:
 44        return torch.zeros((m, 0), device=g.device, dtype=g.dtype), float(initial), 0.0
 45    q = torch.cat(blocks, dim=1)
 46    return q, float(torch.sum(residual * residual)), float(torch.linalg.norm(q.T @ q - torch.eye(q.shape[1], device=g.device, dtype=g.dtype)))
 47
 48
 49def train_one(seed, cfg, idea):
 50    np.random.seed(seed); torch.manual_seed(seed)
 51    # Explicit CPU default avoids shared-GPU contention; CUDA fallback is safe.
 52    device = "cuda" if torch.cuda.is_available() else "cpu"
 53    try:
 54        d = get_dataset("tabular", seed=seed, n_train=400, n_test=200)
 55        net = make_model("mlp_tiny", d["input_shape"], d["out_dim"]).to(device)
 56        xtr, ytr = d["xtr"].to(device), d["ytr"].to(device)
 57        xte, yte = d["xte"].to(device), d["yte"].to(device)
 58        params = list(net.parameters())
 59        # Ordinary Adam moments are baseline; idea stores moments for projected
 60        # gradients only (equivalent reduced-coordinate Adam for each refresh).
 61        opt = torch.optim.Adam(params, lr=float(cfg["lr"]))
 62        rng = torch.Generator(device=device); rng.manual_seed(seed + 991)
 63        last_orth, ranks, proj_ratios = [], [], []
 64        net.train()
 65        for ep in range(EPOCHS):
 66            order = torch.randperm(xtr.shape[0], device=device, generator=rng)
 67            for start in range(0, xtr.shape[0], BATCH):
 68                ix = order[start:start+BATCH]
 69                opt.zero_grad(set_to_none=True)
 70                loss = torch.mean((net(xtr[ix]) - ytr[ix]) ** 2)
 71                loss.backward()
 72                if idea:
 73                    for p in params:
 74                        if p.grad is None or p.ndim != 2:
 75                            continue
 76                        g = p.grad
 77                        q, rem, orth = adaptive_subspace(g, cfg["rel_tol"], cfg["block"], cfg["kmax"], rng)
 78                        if q.shape[1]:
 79                            projected = q @ (q.T @ g)
 80                            p.grad.copy_(projected)
 81                            ranks.append(q.shape[1]); last_orth.append(orth)
 82                            proj_ratios.append(float(torch.linalg.norm(projected) / (torch.linalg.norm(g)+1e-12)))
 83                opt.step()
 84        net.eval()
 85        with torch.no_grad(): metric = float(torch.mean((net(xte) - yte) ** 2).cpu())
 86        stats = {"rank_mean": float(np.mean(ranks)) if ranks else 0.0,
 87                 "orth_mean": float(np.mean(last_orth)) if last_orth else 0.0,
 88                 "projection_ratio": float(np.mean(proj_ratios)) if proj_ratios else 1.0}
 89        return metric, stats
 90    except Exception:
 91        if device == "cuda":
 92            torch.cuda.empty_cache()
 93            # Retry deterministically on CPU after any CUDA failure.
 94            torch.cuda.is_available = lambda: False
 95            return train_one(seed, cfg, idea)
 96        raise
 97
 98
 99def run_eval(cfg, idea, collect=False):
100    stats = []
101    def fn(seed):
102        val, st = train_one(int(seed), cfg, idea)
103        stats.append(st)
104        return val
105    out = evaluate(fn, SEEDS)
106    if collect: out["stats_per_seed"] = stats
107    return out
108
109
110def main():
111    t0 = time.time()
112    # Baseline sweep includes every lr evaluated by the idea (search-space parity).
113    base = sweep_baseline(lambda cfg: lambda seed: train_one(seed, cfg, False)[0],
114                          [{"lr": lr} for lr in LR_GRID], seeds=SEEDS)
115    idea_trials = []
116    for cfg in IDEA_GRID:
117        idea_trials.append({"cfg": cfg, "result": run_eval(cfg, True, collect=True)})
118    best = min(idea_trials, key=lambda z: z["result"]["mean"])
119    base_cfg = base["best_cfg"]
120    # Signature is measured on trained benchmark models: retained rank,
121    # orthogonality, and captured gradient energy, not an analytical toy.
122    sig_stats = best["result"].get("stats_per_seed", [])
123    signature = {
124        "prediction": "adaptive Householder subspaces retain fewer than kmax dimensions while maintaining orthogonality",
125        "observed_rank_mean": float(np.mean([x["rank_mean"] for x in sig_stats])),
126        "observed_orthogonality_mean": float(np.mean([x["orth_mean"] for x in sig_stats])),
127        "observed_projected_gradient_norm_ratio": float(np.mean([x["projection_ratio"] for x in sig_stats])),
128        "confirmed": bool(sig_stats and np.mean([x["orth_mean"] for x in sig_stats]) < 1e-5 and np.mean([x["rank_mean"] for x in sig_stats]) < 16)
129    }
130    # Re-evaluate baseline best and selected idea are already full eight paired seeds.
131    report = make_report("tabular", "mlp_tiny", base, best["result"], {
132        "track_rationale": "optimizer modification matches the tabular optimizer track",
133        "idea_trials": [{"cfg": x["cfg"], "mean": x["result"]["mean"], "std": x["result"]["std"]} for x in idea_trials],
134        "mechanism_signature": signature,
135        "runtime_sec": time.time() - t0
136    })
137    # Required explicit metadata for downstream runner.
138    report["custom_track"] = None
139    Path("bench_report.json").write_text(json.dumps(report, indent=2))
140    print(json.dumps(report, indent=2))
141
142if __name__ == "__main__": main()