libs/data/batch_sampler.py

import tqdm
import copy
import random
from collections import defaultdict
from libs.utils import logger
import numpy as np

class BucketSampler:
    def __init__(self, dataset, world_size, rank_id, fix_batch_size=None, max_pixel_nums=None, max_batch_size=8, min_batch_size=1, seps=(100, 100, 20)):
        self.dataset = dataset
        self.world_size = world_size
        self.rank_id = rank_id
        self.seps = seps
        self.fix_batch_size = fix_batch_size
        self.max_batch_size = max_batch_size
        self.min_batch_size = min_batch_size
        self.max_pixel_nums = max_pixel_nums
        assert (fix_batch_size is not None) or (max_pixel_nums is not None)
        self.cal_buckets()
        self.seed = 20
        self.epoch = 0

def count_keys(self):
    infos = []
    for i in tqdm.tqdm(range(len(self.dataset))):
        info = self.dataset.get_info(i)
        infos.append(info)
    return infos

def cal_buckets(self):
    infos = self.count_keys()
    np.save('count_keys.npy', infos)
    min_sizes = None # (64, 18, 2)
    max_sizes = None # (1223, 742, 2080)
    for info in infos:
        if min_sizes is None:
            min_sizes = info
            max_sizes = info
        else: # get the max size of each item of tuple
            min_sizes = tuple(min(min_sizes[idx], info[idx]) for idx in range(len(min_sizes)))
            max_sizes = tuple(max(max_sizes[idx], info[idx]) for idx in range(len(max_sizes))) 
    assert (min_sizes is not None) and (len(self.seps) == len(min_sizes))
    print('max sizes: {}, min size: {}'.format(max_sizes, min_sizes))
    buckets = defaultdict(list)
    for idx, info in enumerate(infos):
        bucket_idxes = list()
        for sep, size, min_size in zip(self.seps, info, min_sizes):
            bucket_idx = (size - min_size) // sep
            bucket_idxes.append(str(bucket_idx))
        bucket_idxes = '-'.join(bucket_idxes)
        buckets[bucket_idxes].append(idx)
    np.save('buckets.npy', buckets)

    valid_buckets = dict()
    for bucket_key, bucket_samples in buckets.items():
        if len(bucket_samples) < self.min_batch_size:
            continue
        if (self.fix_batch_size is not None) and (len(bucket_samples) < self.fix_batch_size):
            continue

        w, h, *_ = [(int(item) + 1) * sep + min_size for item, min_size, sep in zip(bucket_key.split('-'), min_sizes, self.seps)]
        if self.fix_batch_size is not None:
            if h * w * self.fix_batch_size > self.max_pixel_nums:
                continue
        else:
            if h * w * self.min_batch_size > self.max_pixel_nums:
                continue
        
        if self.fix_batch_size is not None:
            batch_size = self.fix_batch_size
        else:
            batch_size = min(self.max_batch_size, max(self.max_pixel_nums // (w * h), self.min_batch_size), len(bucket_samples))
        
        valid_buckets[bucket_key] = dict(
            samples=bucket_samples,
            batch_size=batch_size
        )

    self.buckets = [valid_buckets[bucket_key] for bucket_key in sorted(valid_buckets.keys())]
    total_nums = len(infos)
    valid_nums = sum([len(item['samples']) for item in valid_buckets.values()])
    logger.info('Total %d samples, but ignore %d samples' % (total_nums, total_nums - valid_nums))

def __iter__(self):
    random_inst = random.Random(self.seed + self.epoch)
    batches = list()
    for bucket in self.buckets:
        sample = copy.deepcopy(bucket['samples'])
        batch_size = bucket['batch_size']
        random_inst.shuffle(sample)
        idx = 0
        while idx < len(sample):
            batch = sample[idx:idx + batch_size]
            idx += batch_size
            if len(batch) < self.min_batch_size:
                continue
            batches.append(batch)
    random_inst.shuffle(batches)
    
    align_nums = (len(batches) // self.world_size) * self.world_size
    batches = batches[: align_nums]
    for batch_idx in range(self.rank_id, len(batches), self.world_size):
        yield batches[batch_idx]

def __len__(self):
    batch_nums = 0
    for bucket in self.buckets:
        bucket_sample_nums = len(bucket["samples"])
        bucket_bs = bucket['batch_size']
        batch_nums += bucket_sample_nums // bucket_bs
        if bucket_sample_nums % bucket_bs >= self.min_batch_size:
            batch_nums += 1

    return batch_nums // self.world_size

def set_epoch(self, epoch):
    self.epoch = epoch