preprocess.py

import numpy as np
import scipy.sparse as sp
import torch


def mask_test_edges(adj):
    # Function to build test set with 10% positive links
    # NOTE: Splits are randomized and results might slightly deviate from reported numbers in the paper.
    # TODO: Clean up.

    # Remove diagonal elements
    adj = adj - sp.dia_matrix(
        (adj.diagonal()[np.newaxis, :], [0]), shape=adj.shape
    )
    adj.eliminate_zeros()
    # Check that diag is zero:
    assert np.diag(adj.todense()).sum() == 0

    adj_triu = sp.triu(adj)
    adj_tuple = sparse_to_tuple(adj_triu)
    edges = adj_tuple[0]
    edges_all = sparse_to_tuple(adj)[0]
    num_test = int(np.floor(edges.shape[0] / 10.0))
    num_val = int(np.floor(edges.shape[0] / 20.0))

    all_edge_idx = list(range(edges.shape[0]))
    np.random.shuffle(all_edge_idx)
    val_edge_idx = all_edge_idx[:num_val]
    test_edge_idx = all_edge_idx[num_val : (num_val + num_test)]
    test_edges = edges[test_edge_idx]
    val_edges = edges[val_edge_idx]
    train_edges = np.delete(
        edges, np.hstack([test_edge_idx, val_edge_idx]), axis=0
    )

    def ismember(a, b, tol=5):
        rows_close = np.all(np.round(a - b[:, None], tol) == 0, axis=-1)
        return np.any(rows_close)

    test_edges_false = []
    while len(test_edges_false) < len(test_edges):
        idx_i = np.random.randint(0, adj.shape[0])
        idx_j = np.random.randint(0, adj.shape[0])
        if idx_i == idx_j:
            continue
        if ismember([idx_i, idx_j], edges_all):
            continue
        if test_edges_false:
            if ismember([idx_j, idx_i], np.array(test_edges_false)):
                continue
            if ismember([idx_i, idx_j], np.array(test_edges_false)):
                continue
        test_edges_false.append([idx_i, idx_j])

    val_edges_false = []
    while len(val_edges_false) < len(val_edges):
        idx_i = np.random.randint(0, adj.shape[0])
        idx_j = np.random.randint(0, adj.shape[0])
        if idx_i == idx_j:
            continue
        if ismember([idx_i, idx_j], train_edges):
            continue
        if ismember([idx_j, idx_i], train_edges):
            continue
        if ismember([idx_i, idx_j], val_edges):
            continue
        if ismember([idx_j, idx_i], val_edges):
            continue
        if val_edges_false:
            if ismember([idx_j, idx_i], np.array(val_edges_false)):
                continue
            if ismember([idx_i, idx_j], np.array(val_edges_false)):
                continue
        val_edges_false.append([idx_i, idx_j])

    assert ~ismember(test_edges_false, edges_all)
    assert ~ismember(val_edges_false, edges_all)
    assert ~ismember(val_edges, train_edges)
    assert ~ismember(test_edges, train_edges)
    assert ~ismember(val_edges, test_edges)

    data = np.ones(train_edges.shape[0])

    # Re-build adj matrix
    adj_train = sp.csr_matrix(
        (data, (train_edges[:, 0], train_edges[:, 1])), shape=adj.shape
    )
    adj_train = adj_train + adj_train.T

    # NOTE: these edge lists only contain single direction of edge!
    return (
        adj_train,
        train_edges,
        val_edges,
        val_edges_false,
        test_edges,
        test_edges_false,
    )


def mask_test_edges_dgl(graph, adj):
    src, dst = graph.edges()
    edges_all = torch.stack([src, dst], dim=0)
    edges_all = edges_all.t().cpu().numpy()
    num_test = int(np.floor(edges_all.shape[0] / 10.0))
    num_val = int(np.floor(edges_all.shape[0] / 20.0))

    all_edge_idx = list(range(edges_all.shape[0]))
    np.random.shuffle(all_edge_idx)
    val_edge_idx = all_edge_idx[:num_val]
    test_edge_idx = all_edge_idx[num_val : (num_val + num_test)]
    train_edge_idx = all_edge_idx[(num_val + num_test) :]
    test_edges = edges_all[test_edge_idx]
    val_edges = edges_all[val_edge_idx]
    train_edges = np.delete(
        edges_all, np.hstack([test_edge_idx, val_edge_idx]), axis=0
    )

    def ismember(a, b, tol=5):
        rows_close = np.all(np.round(a - b[:, None], tol) == 0, axis=-1)
        return np.any(rows_close)

    test_edges_false = []
    while len(test_edges_false) < len(test_edges):
        idx_i = np.random.randint(0, adj.shape[0])
        idx_j = np.random.randint(0, adj.shape[0])
        if idx_i == idx_j:
            continue
        if ismember([idx_i, idx_j], edges_all):
            continue
        if test_edges_false:
            if ismember([idx_j, idx_i], np.array(test_edges_false)):
                continue
            if ismember([idx_i, idx_j], np.array(test_edges_false)):
                continue
        test_edges_false.append([idx_i, idx_j])

    val_edges_false = []
    while len(val_edges_false) < len(val_edges):
        idx_i = np.random.randint(0, adj.shape[0])
        idx_j = np.random.randint(0, adj.shape[0])
        if idx_i == idx_j:
            continue
        if ismember([idx_i, idx_j], train_edges):
            continue
        if ismember([idx_j, idx_i], train_edges):
            continue
        if ismember([idx_i, idx_j], val_edges):
            continue
        if ismember([idx_j, idx_i], val_edges):
            continue
        if val_edges_false:
            if ismember([idx_j, idx_i], np.array(val_edges_false)):
                continue
            if ismember([idx_i, idx_j], np.array(val_edges_false)):
                continue
        val_edges_false.append([idx_i, idx_j])

    assert ~ismember(test_edges_false, edges_all)
    assert ~ismember(val_edges_false, edges_all)
    assert ~ismember(val_edges, train_edges)
    assert ~ismember(test_edges, train_edges)
    assert ~ismember(val_edges, test_edges)

    # NOTE: these edge lists only contain single direction of edge!
    return (
        train_edge_idx,
        val_edges,
        val_edges_false,
        test_edges,
        test_edges_false,
    )


def sparse_to_tuple(sparse_mx):
    if not sp.isspmatrix_coo(sparse_mx):
        sparse_mx = sparse_mx.tocoo()
    coords = np.vstack((sparse_mx.row, sparse_mx.col)).transpose()
    values = sparse_mx.data
    shape = sparse_mx.shape
    return coords, values, shape


def preprocess_graph(adj):
    adj = sp.coo_matrix(adj)
    adj_ = adj + sp.eye(adj.shape[0])
    rowsum = np.array(adj_.sum(1))
    degree_mat_inv_sqrt = sp.diags(np.power(rowsum, -0.5).flatten())
    adj_normalized = (
        adj_.dot(degree_mat_inv_sqrt)
        .transpose()
        .dot(degree_mat_inv_sqrt)
        .tocoo()
    )
    return adj_normalized, sparse_to_tuple(adj_normalized)