nuonuo/experiments/exp07b_hopfield_deep.py

"""Experiment 7b: Deep dive into Hopfield memory.

Hopfield crushed it at 1000 bg (100% para recall). Now stress test:
1. Scale to 5K, 10K, 20K memories — does softmax attention hold up?
2. Multi-hop: can we chain through Hopfield? (A→B→C)
3. Latency: O(N) attention — how slow at 20K?
4. β optimization: find sweet spot
5. Memory: storing all patterns explicitly — how much VRAM?
6. Mixed difficulty: semantically similar distractors (not just random bg)
"""

import sys
import time
from pathlib import Path

import torch
import torch.nn as nn
import numpy as np

DEVICE = "cuda"


def cosine(a, b):
    if a.norm() == 0 or b.norm() == 0:
        return 0.0
    return nn.functional.cosine_similarity(a.unsqueeze(0), b.unsqueeze(0)).item()


def winner_take_all(x, k):
    _, idx = x.topk(k, dim=-1)
    out = torch.zeros_like(x)
    out.scatter_(-1, idx, 1.0)
    return out


class HopfieldMemory:
    def __init__(self, input_dim, code_dim=16384, k=50, beta=16.0):
        self.k = k
        self.code_dim = code_dim
        self.beta = beta
        self.proj = (torch.randn(input_dim, code_dim, device=DEVICE)
                     * (1.0 / input_dim**0.5))
        self.cue_codes = []
        self.target_codes = []
        self.cue_embs = []
        self.target_embs = []

    def sep(self, x):
        return winner_take_all(x @ self.proj, self.k)

    def learn(self, cue_emb, target_emb):
        self.cue_codes.append(self.sep(cue_emb))
        self.target_codes.append(self.sep(target_emb))
        self.cue_embs.append(cue_emb.detach())
        self.target_embs.append(target_emb.detach())

    def _get_matrices(self):
        return torch.stack(self.cue_codes), torch.stack(self.target_codes)

    def recall(self, query_emb, steps=3):
        cue_mat, target_mat = self._get_matrices()
        xi = self.sep(query_emb)
        for _ in range(steps):
            scores = self.beta * (xi @ cue_mat.T)
            attn = torch.softmax(scores, dim=0)
            xi = attn @ cue_mat
            xi = winner_take_all(xi, self.k)
        # Final association
        scores = self.beta * (xi @ cue_mat.T)
        attn = torch.softmax(scores, dim=0)
        recalled = attn @ target_mat
        return winner_take_all(recalled, self.k)

    def recall_multihop(self, query_emb, hops=2, steps_per_hop=3):
        """Multi-hop: settle to cue → get target → use target as next cue."""
        cue_mat, target_mat = self._get_matrices()

        xi = self.sep(query_emb)
        results = []

        for hop in range(hops):
            # Settle to nearest cue attractor
            for _ in range(steps_per_hop):
                scores = self.beta * (xi @ cue_mat.T)
                attn = torch.softmax(scores, dim=0)
                xi = attn @ cue_mat
                xi = winner_take_all(xi, self.k)

            # Associate: cue → target
            scores = self.beta * (xi @ cue_mat.T)
            attn = torch.softmax(scores, dim=0)
            target = attn @ target_mat
            target = winner_take_all(target, self.k)
            results.append(target)

            # Next hop: use target as new query
            xi = target

        return results

    def recall_embedding_space(self, query_emb, steps=3):
        """Hopfield attention in raw embedding space (no WTA codes).
        Might be better for noise tolerance since embeddings are continuous.
        """
        if not self.cue_embs:
            return None

        cue_mat = torch.stack(self.cue_embs)
        target_mat = torch.stack(self.target_embs)

        xi = query_emb
        for _ in range(steps):
            scores = self.beta * (xi @ cue_mat.T)
            attn = torch.softmax(scores, dim=0)
            xi = attn @ cue_mat

        # Final: get target
        scores = self.beta * (xi @ cue_mat.T)
        attn = torch.softmax(scores, dim=0)
        return attn @ target_mat


def load_model():
    from sentence_transformers import SentenceTransformer
    return SentenceTransformer("all-MiniLM-L6-v2", device=DEVICE)


def test_scale(model, n_background_list, beta=16.0):
    """Test Hopfield at different scales."""
    print(f"\n=== Scale Test (β={beta}) ===")

    pairs = [
        ("What's the weather like today?", "User checks weather every morning"),
        ("Let's deploy the new version", "Deployment uses GitHub Actions with k3s"),
        ("The database is slow again", "Missing index on users table"),
        ("I need to fix the auth bug", "JWT tokens with 24h expiry in Redis"),
        ("The API returns 500 errors", "OOM in the Python worker"),
    ]
    paraphrases = [
        "How's the weather outside?",
        "We should push the new release",
        "DB performance is terrible",
        "There's a login bug to fix",
        "Getting internal server errors",
    ]

    embed_dim = model.get_sentence_embedding_dimension()
    cue_embs = model.encode([p[0] for p in pairs], convert_to_tensor=True,
                             normalize_embeddings=True, device=DEVICE)
    target_embs = model.encode([p[1] for p in pairs], convert_to_tensor=True,
                                normalize_embeddings=True, device=DEVICE)
    para_embs = model.encode(paraphrases, convert_to_tensor=True,
                              normalize_embeddings=True, device=DEVICE)

    for n_bg in n_background_list:
        mem = HopfieldMemory(embed_dim, code_dim=8192, k=50, beta=beta)

        # Store test pairs
        for i in range(len(pairs)):
            mem.learn(cue_embs[i], target_embs[i])

        # Store background
        if n_bg > 0:
            # More diverse background sentences
            bg_cues = []
            bg_targets = []
            topics = ["server", "database", "API", "frontend", "backend",
                      "cache", "queue", "network", "storage", "auth"]
            for i in range(n_bg):
                t = topics[i % len(topics)]
                bg_cues.append(f"The {t} system has issue number {i}")
                bg_targets.append(f"Issue {i} for {t} requires attention from team {i%5}")

            for start in range(0, n_bg, 256):
                end = min(start + 256, n_bg)
                bc = model.encode(bg_cues[start:end], convert_to_tensor=True,
                                   normalize_embeddings=True, device=DEVICE)
                bt = model.encode(bg_targets[start:end], convert_to_tensor=True,
                                   normalize_embeddings=True, device=DEVICE)
                for j in range(bc.shape[0]):
                    mem.learn(bc[j], bt[j])

        # Test
        target_codes = torch.stack([mem.sep(t) for t in target_embs])

        # Paraphrase recall
        t0 = time.time()
        para_correct = 0
        for i in range(len(paraphrases)):
            recalled = mem.recall(para_embs[i])
            sims = nn.functional.cosine_similarity(recalled.unsqueeze(0), target_codes, dim=-1)
            if sims.argmax().item() == i:
                para_correct += 1
        recall_time = (time.time() - t0) / len(paraphrases) * 1000

        # Also test in embedding space
        para_correct_emb = 0
        for i in range(len(paraphrases)):
            recalled_emb = mem.recall_embedding_space(para_embs[i])
            sims = nn.functional.cosine_similarity(recalled_emb.unsqueeze(0), target_embs, dim=-1)
            if sims.argmax().item() == i:
                para_correct_emb += 1

        n = len(paraphrases)
        total_mem = len(mem.cue_codes)
        vram = total_mem * 8192 * 4 * 2 / 1024**2  # codes + embs approx
        print(f"  N={total_mem:>6}: Code={para_correct}/{n} ({para_correct/n:.0%}), "
              f"Emb={para_correct_emb}/{n} ({para_correct_emb/n:.0%}), "
              f"time={recall_time:.1f}ms, ~VRAM={vram:.0f}MB")

        del mem
        torch.cuda.empty_cache()


def test_multihop(model):
    """Multi-hop through Hopfield memory."""
    print("\n=== Multi-hop Test ===")

    chains = [
        ["What's the weather?", "I check weather before going out",
         "My coffee shop is around the corner", "They have great latte art"],
        ["Let's review the code", "Code review found a memory leak",
         "Memory leaks cause OOM kills", "Need memory limits in k8s"],
        ["Deploy to production", "Production uses blue-green deploy",
         "Blue environment is active", "Switch DNS to green when ready"],
    ]

    embed_dim = model.get_sentence_embedding_dimension()

    for chain in chains:
        mem = HopfieldMemory(embed_dim, code_dim=8192, k=50, beta=16.0)

        chain_embs = [model.encode([t], convert_to_tensor=True,
                                    normalize_embeddings=True, device=DEVICE)[0]
                      for t in chain]

        # Learn consecutive pairs
        for i in range(len(chain) - 1):
            mem.learn(chain_embs[i], chain_embs[i+1])

        # Multi-hop recall
        target_codes = [mem.sep(e) for e in chain_embs]

        results = mem.recall_multihop(chain_embs[0], hops=len(chain)-1)

        print(f"\n  Chain: {' → '.join([c[:20]+'...' for c in chain])}")
        for hop_idx, recalled in enumerate(results):
            target = target_codes[hop_idx + 1]
            sim = cosine(recalled, target)
            status = "✓" if sim > 0.5 else "✗"
            print(f"    {status} hop {hop_idx+1}: → '{chain[hop_idx+1][:30]}...' sim={sim:.3f}")

    # Multi-hop with background noise
    print("\n  --- Multi-hop with 200 background memories ---")
    mem = HopfieldMemory(embed_dim, code_dim=8192, k=50, beta=16.0)

    # Store all chains
    all_chain_embs = []
    for chain in chains:
        embs = [model.encode([t], convert_to_tensor=True,
                              normalize_embeddings=True, device=DEVICE)[0]
                for t in chain]
        all_chain_embs.append(embs)
        for i in range(len(chain) - 1):
            mem.learn(embs[i], embs[i+1])

    # Add background
    bg = [f"Background sentence number {i}" for i in range(200)]
    bg_embs = model.encode(bg, convert_to_tensor=True,
                            normalize_embeddings=True, device=DEVICE)
    for i in range(199):
        mem.learn(bg_embs[i], bg_embs[i+1])

    for ci, chain in enumerate(chains):
        target_codes = [mem.sep(e) for e in all_chain_embs[ci]]
        results = mem.recall_multihop(all_chain_embs[ci][0], hops=len(chain)-1)

        for hop_idx, recalled in enumerate(results):
            target = target_codes[hop_idx + 1]
            sim = cosine(recalled, target)
            status = "✓" if sim > 0.5 else "✗"
            print(f"    {status} Chain{ci+1} hop{hop_idx+1}: sim={sim:.3f}")


def test_hard_distractors(model):
    """Test with semantically similar distractors (harder than random bg)."""
    print("\n=== Hard Distractors (semantically similar) ===")

    # Target pair
    pairs = [
        ("The database is slow", "Missing index on users table"),
    ]
    # Distractors: similar to cue but different meaning
    distractors_cue = [
        "The database is fast",
        "The database crashed",
        "The database needs backup",
        "The datastore is slow",
        "The DB latency is high",
        "Database performance degraded",
        "SQL queries are slow",
        "The cache is slow",
        "The search index is slow",
        "MongoDB is slow",
    ]
    distractors_target = [
        f"Distractor target {i}" for i in range(len(distractors_cue))
    ]

    query = "DB performance is terrible"

    embed_dim = model.get_sentence_embedding_dimension()

    for beta in [8.0, 16.0, 32.0, 64.0]:
        mem = HopfieldMemory(embed_dim, code_dim=8192, k=50, beta=beta)

        # Store target
        cue_emb = model.encode([pairs[0][0]], convert_to_tensor=True,
                                normalize_embeddings=True, device=DEVICE)[0]
        target_emb = model.encode([pairs[0][1]], convert_to_tensor=True,
                                   normalize_embeddings=True, device=DEVICE)[0]
        mem.learn(cue_emb, target_emb)

        # Store distractors
        dist_cue_embs = model.encode(distractors_cue, convert_to_tensor=True,
                                      normalize_embeddings=True, device=DEVICE)
        dist_target_embs = model.encode(distractors_target, convert_to_tensor=True,
                                         normalize_embeddings=True, device=DEVICE)
        for i in range(len(distractors_cue)):
            mem.learn(dist_cue_embs[i], dist_target_embs[i])

        # Query
        q_emb = model.encode([query], convert_to_tensor=True,
                              normalize_embeddings=True, device=DEVICE)[0]
        recalled = mem.recall(q_emb)
        target_code = mem.sep(target_emb)
        sim = cosine(recalled, target_code)

        # Also check which cue got highest attention
        cue_mat = torch.stack(mem.cue_codes)
        q_code = mem.sep(q_emb)
        scores = beta * (q_code @ cue_mat.T)
        attn = torch.softmax(scores, dim=0)
        top_idx = attn.argmax().item()
        top_attn = attn[top_idx].item()

        all_cues = [pairs[0][0]] + distractors_cue
        print(f"  β={beta:>4}: sim_to_target={sim:.3f}, "
              f"top_attn={top_attn:.3f} → '{all_cues[top_idx][:30]}...'")


def main():
    print("=" * 60)
    print("Experiment 7b: Hopfield Deep Dive")
    print("=" * 60)

    model = load_model()

    # Scale test
    test_scale(model, [0, 100, 500, 1000, 2000, 5000, 10000], beta=16.0)

    # β sweep at large scale
    print("\n=== β Sweep at N=5000 ===")
    for beta in [4, 8, 16, 32, 64]:
        test_scale(model, [5000], beta=beta)

    # Multi-hop
    test_multihop(model)

    # Hard distractors
    test_hard_distractors(model)


if __name__ == "__main__":
    main()