code/run_lgcn_final.py

"""Final optimized submission: LightGCN-only ensemble, saved to disk."""
import os
import pickle as pkl
import random

import numpy as np
import pandas as pd
import torch
import torch.nn as nn
import torch.nn.functional as F

from torch_geometric.data import HeteroData
from numpy.linalg import norm

device = torch.device('cuda:0' if torch.cuda.is_available() else 'cpu')
print('device:', device)


def set_seed(seed=0):
    random.seed(seed)
    np.random.seed(seed)
    torch.manual_seed(seed)
    if torch.cuda.is_available():
        torch.cuda.manual_seed_all(seed)


# ── Data ──────────────────────────────────────────────────────────
base_path = "/home/lzc/cs3319-project"


def read_txt(file):
    res_list = []
    with open(file, "r") as f:
        for line in f:
            res_list.append(list(map(int, line.strip().split())))
    return res_list


citation = read_txt(os.path.join(base_path, "paper_file_ann.txt"))
existing_refs = read_txt(os.path.join(base_path, "bipartite_train_ann.txt"))
refs_to_pred = read_txt(os.path.join(base_path, "bipartite_test_ann.txt"))
coauthor = read_txt(os.path.join(base_path, "author_file_ann.txt"))
with open(os.path.join(base_path, "feature.pkl"), 'rb') as f:
    paper_feature = pkl.load(f)

# Pre-process
cite_edges = pd.DataFrame(citation, columns=['source', 'target'])
ref_edges = pd.DataFrame(existing_refs, columns=['source', 'target'])
coauthor_edges = pd.DataFrame(coauthor, columns=['source', 'target'])
node_tmp = pd.concat([cite_edges['source'], cite_edges['target'], ref_edges['target']])
node_papers = pd.DataFrame(index=pd.unique(node_tmp))
node_tmp = pd.concat([ref_edges['source'], coauthor_edges['source'], coauthor_edges['target']])
node_authors = pd.DataFrame(index=pd.unique(node_tmp))
num_authors = len(node_authors)
num_papers = len(node_papers)
print(f"Nodes: {num_authors} authors, {num_papers} papers")

# Degree features
author_ref_deg = np.zeros(num_authors, dtype=np.float32)
paper_ref_deg = np.zeros(num_papers, dtype=np.float32)
paper_cite_out = np.zeros(num_papers, dtype=np.float32)
paper_cite_in = np.zeros(num_papers, dtype=np.float32)
for s, t in existing_refs:
    author_ref_deg[s] += 1
    paper_ref_deg[t] += 1
for s, t in citation:
    paper_cite_out[s] += 1
    paper_cite_in[t] += 1


def log_norm(x):
    x = np.log1p(x)
    return (x - x.mean()) / (x.std() + 1e-8)


paper_feat_np = paper_feature.numpy().astype(np.float32)
paper_deg_feat = np.stack([log_norm(paper_ref_deg), log_norm(paper_cite_out),
                           log_norm(paper_cite_in)], axis=-1)
paper_feat_aug = np.concatenate([paper_feat_np, paper_deg_feat], axis=-1)
paper_feat_aug = (paper_feat_aug - paper_feat_aug.mean(axis=0)) / (paper_feat_aug.std(axis=0) + 1e-8)

# Hard negative pools
popular_threshold = np.percentile(paper_ref_deg[paper_ref_deg > 0], 70)
popular_papers = np.where(paper_ref_deg >= popular_threshold)[0]
coauthor_map = {i: set() for i in range(num_authors)}
for s, t in coauthor:
    coauthor_map[s].add(t)
    coauthor_map[t].add(s)
author_papers = {i: set() for i in range(num_authors)}
for s, t in existing_refs:
    author_papers[s].add(t)
coauthor_paper_pool = {}
for a in range(num_authors):
    pool = set()
    for c in coauthor_map[a]:
        pool.update(author_papers[c])
    pool -= author_papers[a]
    coauthor_paper_pool[a] = list(pool) if pool else list(range(num_papers))

existing_ref_set = set(map(tuple, existing_refs))

# Train-test overlap
train_set = set(map(tuple, existing_refs))
overlap = train_set & set(map(tuple, refs_to_pred))
print(f"Known positives: {len(overlap)}")


# ── Build graph ───────────────────────────────────────────────────
def build_data(ref_edges_use):
    ref_tensor = torch.as_tensor(ref_edges_use[['source', 'target']].to_numpy(), dtype=torch.long)
    cite_tensor = torch.as_tensor(cite_edges[['source', 'target']].to_numpy(), dtype=torch.long)
    coauthor_tensor = torch.as_tensor(coauthor_edges[['source', 'target']].to_numpy(), dtype=torch.long)

    d = HeteroData()
    d['author'].num_nodes = num_authors
    d['paper'].num_nodes = num_papers
    d['paper'].x = torch.as_tensor(paper_feat_aug, dtype=torch.float)
    d['author', 'ref', 'paper'].edge_index = ref_tensor.t().contiguous()
    d['paper', 'beref', 'author'].edge_index = ref_tensor[:, [1, 0]].t().contiguous()
    d['paper', 'cite', 'paper'].edge_index = torch.cat([
        cite_tensor, cite_tensor[:, [1, 0]]], dim=0).t().contiguous()
    d['author', 'coauthor', 'author'].edge_index = torch.cat([
        coauthor_tensor, coauthor_tensor[:, [1, 0]]], dim=0).t().contiguous()
    return d.to(device)


def sample_hard_negatives(n_samples):
    neg_list = []

    def add_random(target):
        nonlocal neg_list
        while len(neg_list) < target:
            s = np.random.randint(0, num_authors)
            d = np.random.randint(0, num_papers)
            if (s, d) not in existing_ref_set:
                neg_list.append((s, d))

    add_random(int(n_samples * 0.5))
    cnt = 0
    while len(neg_list) < int(n_samples * 0.75) and cnt < n_samples * 2:
        cnt += 1
        s = np.random.randint(0, num_authors)
        d = popular_papers[np.random.randint(0, len(popular_papers))]
        if (s, d) not in existing_ref_set:
            neg_list.append((s, d))
    cnt = 0
    while len(neg_list) < n_samples and cnt < n_samples * 3:
        cnt += 1
        s = np.random.randint(0, num_authors)
        pool = coauthor_paper_pool.get(s, [])
        if pool:
            d = pool[np.random.randint(0, len(pool))]
            if (s, d) not in existing_ref_set:
                neg_list.append((s, d))
    add_random(n_samples)
    return torch.tensor(neg_list[:n_samples], dtype=torch.long, device=device).t().contiguous()


# ── LightGCN Model ────────────────────────────────────────────────
class LightGCNLayer(nn.Module):
    def __init__(self):
        super().__init__()
        self.ets = [('author', 'ref', 'paper'), ('paper', 'beref', 'author'),
                    ('paper', 'cite', 'paper'), ('author', 'coauthor', 'author')]

    def forward(self, x_dict, edge_index_dict):
        agg_dict = {nt: [] for nt in x_dict}
        for et in self.ets:
            if et not in edge_index_dict:
                continue
            st, _, dt = et
            src, dst = edge_index_dict[et]
            sx = x_dict[st]
            a = sx.new_zeros((x_dict[dt].size(0), sx.size(-1)))
            d = sx.new_zeros((x_dict[dt].size(0), 1))
            a.index_add_(0, dst, sx[src])
            d.index_add_(0, dst, torch.ones((dst.numel(), 1), dtype=sx.dtype, device=sx.device))
            agg_dict[dt].append(a / d.clamp(min=1.0))
        return {nt: sum(agg_dict[nt]) / len(agg_dict[nt]) if agg_dict[nt] else x_dict[nt]
                for nt in x_dict}


class LightGCN(nn.Module):
    def __init__(self, embed_dim=256, num_layers=4):
        super().__init__()
        self.author_emb = nn.Embedding(num_authors, embed_dim)
        self.paper_proj = nn.Linear(paper_feat_aug.shape[1], embed_dim)
        self.layers = nn.ModuleList([LightGCNLayer() for _ in range(num_layers)])
        self.num_layers = num_layers
        self.reset_parameters()

    def reset_parameters(self):
        nn.init.xavier_uniform_(self.author_emb.weight)
        nn.init.xavier_uniform_(self.paper_proj.weight)
        nn.init.zeros_(self.paper_proj.bias)

    def encode(self, data):
        x_dict = {'author': self.author_emb.weight,
                  'paper': self.paper_proj(data['paper'].x)}
        all_layers = [x_dict]
        for layer in self.layers:
            x_dict = layer(x_dict, data.edge_index_dict)
            all_layers.append(x_dict)
        w = 1.0 / (self.num_layers + 1)
        return {nt: sum(w * l[nt] for l in all_layers) for nt in x_dict}

    def decode(self, z_dict, edge_index):
        src, dst = edge_index
        return (z_dict['author'][src] * z_dict['paper'][dst]).sum(dim=-1)


def cos_sim(a, b, eps=1e-12):
    return np.sum(a * b, axis=1) / (norm(a, axis=1) * norm(b, axis=1) + eps)


@torch.no_grad()
def predict_batched(model, data, pairs, batch_size=65536):
    model.eval()
    z_dict = model.encode(data)
    z_cpu = {k: v.cpu() for k, v in z_dict.items()}
    all_scores = []
    for start in range(0, len(pairs), batch_size):
        end = min(start + batch_size, len(pairs))
        batch = pairs[start:end]
        all_scores.append(cos_sim(
            z_cpu['author'][batch[:, 0]].numpy(),
            z_cpu['paper'][batch[:, 1]].numpy()))
    return np.concatenate(all_scores)


# ── Training ──────────────────────────────────────────────────────
def train_lgcn(seed, embed_dim=256, num_layers=4, lr=0.005, epochs=200):
    set_seed(seed)
    data = build_data(ref_edges)
    model = LightGCN(embed_dim, num_layers).to(device)
    optimizer = torch.optim.Adam(model.parameters(), lr=lr, weight_decay=1e-5)
    pos_edges = data['author', 'ref', 'paper'].edge_index
    bs = min(32768, pos_edges.size(1))

    for ep in range(epochs):
        model.train()
        perm = torch.randperm(pos_edges.size(1), device=device)[:bs]
        pos = pos_edges[:, perm]
        neg = sample_hard_negatives(pos.size(1) * 2)

        z = model.encode(data)
        pos_s = model.decode(z, pos).repeat_interleave(2)
        neg_s = model.decode(z, neg)
        loss = -F.logsigmoid(pos_s - neg_s).mean()

        optimizer.zero_grad()
        loss.backward()
        torch.nn.utils.clip_grad_norm_(model.parameters(), 1.0)
        optimizer.step()

        if ep % 50 == 0 or ep == epochs - 1:
            print(f'  [{seed}] ep={ep:03d} loss={loss.item():.4f}')

    # Save model
    save_path = f'/home/lzc/model_lgcn_s{seed}.pt'
    torch.save(model.state_dict(), save_path)
    print(f'  Saved: {save_path}')
    return model.cpu(), data


# ── Main ──────────────────────────────────────────────────────────
test_arr = np.array(refs_to_pred, dtype=np.int64)
seeds = [0, 42, 2024, 10, 100]
models = []

for seed in seeds:
    print(f"\n{'='*50}\nTraining LightGCN seed={seed}\n{'='*50}")
    m, d = train_lgcn(seed, embed_dim=256, num_layers=4, epochs=200)
    models.append((m, d))

# ── Prediction ────────────────────────────────────────────────────
print(f"\n{'='*50}\nGenerating ensemble predictions\n{'='*50}")
data_full = build_data(ref_edges)

all_scores = []
for i, (model, _) in enumerate(models):
    model = model.to(device)
    scores = predict_batched(model, data_full, test_arr)
    all_scores.append(scores)
    print(f"  Model s={seeds[i]}: mean_cos={scores.mean():.4f} std={scores.std():.4f}")
    model.cpu()

ensemble = np.mean(all_scores, axis=0)

# Force known positives
known_mask = np.array([tuple(p) in overlap for p in refs_to_pred])
ensemble[known_mask] = 1.0

print(f"\nEnsemble stats: mean={ensemble.mean():.4f} min={ensemble.min():.4f} max={ensemble.max():.4f}")
print(f"Known positives: {known_mask.sum()}")

# Generate submissions at multiple thresholds
thresholds = [0.30, 0.32, 0.34, 0.35, 0.36, 0.37, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50]
for thresh in thresholds:
    preds = (ensemble >= thresh).astype(int)
    ratio = preds.mean()
    extra = preds.sum() - known_mask.sum()
    path = f"/home/lzc/sub_lgcn_t{thresh:.2f}.csv"
    data_out = [[idx, str(int(p))] for idx, p in enumerate(preds)]
    pd.DataFrame(data_out, columns=['Index', 'Predicted'], dtype=object).to_csv(path, index=False)
    print(f"  t={thresh:.2f}: pos={ratio:.4f} ({preds.sum()}), extra={extra}")

print("\nDone! Upload these files to find the best threshold.")