train_searcher.py

import argparse
import glob
import os
import sys
from multiprocessing import cpu_count

import numpy as np
import scann
from ldm.util import parallel_data_prefetch
from tqdm import tqdm


def search_bruteforce(searcher):
    return searcher.score_brute_force().build()


def search_partioned_ah(
    searcher, dims_per_block, aiq_threshold, reorder_k, partioning_trainsize, num_leaves, num_leaves_to_search
):
    return (
        searcher.tree(
            num_leaves=num_leaves, num_leaves_to_search=num_leaves_to_search, training_sample_size=partioning_trainsize
        )
        .score_ah(dims_per_block, anisotropic_quantization_threshold=aiq_threshold)
        .reorder(reorder_k)
        .build()
    )


def search_ah(searcher, dims_per_block, aiq_threshold, reorder_k):
    return (
        searcher.score_ah(dims_per_block, anisotropic_quantization_threshold=aiq_threshold).reorder(reorder_k).build()
    )


def load_datapool(dpath):
    def load_single_file(saved_embeddings):
        compressed = np.load(saved_embeddings)
        database = {key: compressed[key] for key in compressed.files}
        return database

    def load_multi_files(data_archive):
        database = {key: [] for key in data_archive[0].files}
        for d in tqdm(data_archive, desc=f"Loading datapool from {len(data_archive)} individual files."):
            for key in d.files:
                database[key].append(d[key])

        return database

    print(f'Load saved patch embedding from "{dpath}"')
    file_content = glob.glob(os.path.join(dpath, "*.npz"))

    if len(file_content) == 1:
        data_pool = load_single_file(file_content[0])
    elif len(file_content) > 1:
        data = [np.load(f) for f in file_content]
        prefetched_data = parallel_data_prefetch(
            load_multi_files, data, n_proc=min(len(data), cpu_count()), target_data_type="dict"
        )

        data_pool = {
            key: np.concatenate([od[key] for od in prefetched_data], axis=1)[0] for key in prefetched_data[0].keys()
        }
    else:
        raise ValueError(f'No npz-files in specified path "{dpath}" is this directory existing?')

    print(f'Finished loading of retrieval database of length {data_pool["embedding"].shape[0]}.')
    return data_pool


def train_searcher(
    opt,
    metric="dot_product",
    partioning_trainsize=None,
    reorder_k=None,
    # todo tune
    aiq_thld=0.2,
    dims_per_block=2,
    num_leaves=None,
    num_leaves_to_search=None,
):
    data_pool = load_datapool(opt.database)
    k = opt.knn

    if not reorder_k:
        reorder_k = 2 * k

    # normalize
    # embeddings =
    searcher = scann.scann_ops_pybind.builder(
        data_pool["embedding"] / np.linalg.norm(data_pool["embedding"], axis=1)[:, np.newaxis], k, metric
    )
    pool_size = data_pool["embedding"].shape[0]

    print(*(["#"] * 100))
    print("Initializing scaNN searcher with the following values:")
    print(f"k: {k}")
    print(f"metric: {metric}")
    print(f"reorder_k: {reorder_k}")
    print(f"anisotropic_quantization_threshold: {aiq_thld}")
    print(f"dims_per_block: {dims_per_block}")
    print(*(["#"] * 100))
    print("Start training searcher....")
    print(f"N samples in pool is {pool_size}")

    # this reflects the recommended design choices proposed at
    # https://github.com/google-research/google-research/blob/aca5f2e44e301af172590bb8e65711f0c9ee0cfd/scann/docs/algorithms.md
    if pool_size < 2e4:
        print("Using brute force search.")
        searcher = search_bruteforce(searcher)
    elif 2e4 <= pool_size and pool_size < 1e5:
        print("Using asymmetric hashing search and reordering.")
        searcher = search_ah(searcher, dims_per_block, aiq_thld, reorder_k)
    else:
        print("Using using partioning, asymmetric hashing search and reordering.")

        if not partioning_trainsize:
            partioning_trainsize = data_pool["embedding"].shape[0] // 10
        if not num_leaves:
            num_leaves = int(np.sqrt(pool_size))

        if not num_leaves_to_search:
            num_leaves_to_search = max(num_leaves // 20, 1)

        print("Partitioning params:")
        print(f"num_leaves: {num_leaves}")
        print(f"num_leaves_to_search: {num_leaves_to_search}")
        # self.searcher = self.search_ah(searcher, dims_per_block, aiq_thld, reorder_k)
        searcher = search_partioned_ah(
            searcher, dims_per_block, aiq_thld, reorder_k, partioning_trainsize, num_leaves, num_leaves_to_search
        )

    print("Finish training searcher")
    searcher_savedir = opt.target_path
    os.makedirs(searcher_savedir, exist_ok=True)
    searcher.serialize(searcher_savedir)
    print(f'Saved trained searcher under "{searcher_savedir}"')


if __name__ == "__main__":
    sys.path.append(os.getcwd())
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--database",
        "-d",
        default="data/rdm/retrieval_databases/openimages",
        type=str,
        help="path to folder containing the clip feature of the database",
    )
    parser.add_argument(
        "--target_path",
        "-t",
        default="data/rdm/searchers/openimages",
        type=str,
        help="path to the target folder where the searcher shall be stored.",
    )
    parser.add_argument(
        "--knn",
        "-k",
        default=20,
        type=int,
        help="number of nearest neighbors, for which the searcher shall be optimized",
    )

    opt, _ = parser.parse_known_args()

    train_searcher(
        opt,
    )