--- a
+++ b/tools/train.py
@@ -0,0 +1,209 @@
+# Copyright (c) OpenMMLab. All rights reserved.
+import argparse
+import copy
+import os
+import os.path as osp
+import time
+import warnings
+
+import mmcv
+import torch
+from mmcv.cnn.utils import revert_sync_batchnorm
+from mmcv.runner import get_dist_info, init_dist
+from mmcv.utils import Config, DictAction, get_git_hash
+
+from mmseg import __version__
+from mmseg.apis import init_random_seed, set_random_seed, train_segmentor
+from mmseg.datasets import build_dataset
+from mmseg.models import build_segmentor
+from mmseg.utils import collect_env, get_root_logger
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(description='Train a segmentor')
+    parser.add_argument('config', help='train config file path')
+    parser.add_argument('--work-dir', help='the dir to save logs and models')
+    parser.add_argument(
+        '--load-from', help='the checkpoint file to load weights from')
+    parser.add_argument(
+        '--resume-from', help='the checkpoint file to resume from')
+    parser.add_argument(
+        '--no-validate',
+        action='store_true',
+        help='whether not to evaluate the checkpoint during training')
+    group_gpus = parser.add_mutually_exclusive_group()
+    group_gpus.add_argument(
+        '--gpus',
+        type=int,
+        help='number of gpus to use '
+        '(only applicable to non-distributed training)')
+    group_gpus.add_argument(
+        '--gpu-ids',
+        type=int,
+        nargs='+',
+        help='ids of gpus to use '
+        '(only applicable to non-distributed training)')
+    parser.add_argument('--seed', type=int, default=None, help='random seed')
+    parser.add_argument(
+        '--deterministic',
+        action='store_true',
+        help='whether to set deterministic options for CUDNN backend.')
+    parser.add_argument(
+        '--options',
+        nargs='+',
+        action=DictAction,
+        help="--options is deprecated in favor of --cfg_options' and it will "
+        'not be supported in version v0.22.0. Override some settings in the '
+        'used config, the key-value pair in xxx=yyy format will be merged '
+        'into config file. If the value to be overwritten is a list, it '
+        'should be like key="[a,b]" or key=a,b It also allows nested '
+        'list/tuple values, e.g. key="[(a,b),(c,d)]" Note that the quotation '
+        'marks are necessary and that no white space is allowed.')
+    parser.add_argument(
+        '--cfg-options',
+        nargs='+',
+        action=DictAction,
+        help='override some settings in the used config, the key-value pair '
+        'in xxx=yyy format will be merged into config file. If the value to '
+        'be overwritten is a list, it should be like key="[a,b]" or key=a,b '
+        'It also allows nested list/tuple values, e.g. key="[(a,b),(c,d)]" '
+        'Note that the quotation marks are necessary and that no white space '
+        'is allowed.')
+    parser.add_argument(
+        '--launcher',
+        choices=['none', 'pytorch', 'slurm', 'mpi'],
+        default='none',
+        help='job launcher')
+    parser.add_argument('--local_rank', type=int, default=0)
+    args = parser.parse_args()
+    if 'LOCAL_RANK' not in os.environ:
+        os.environ['LOCAL_RANK'] = str(args.local_rank)
+
+    if args.options and args.cfg_options:
+        raise ValueError(
+            '--options and --cfg-options cannot be both '
+            'specified, --options is deprecated in favor of --cfg-options. '
+            '--options will not be supported in version v0.22.0.')
+    if args.options:
+        warnings.warn('--options is deprecated in favor of --cfg-options. '
+                      '--options will not be supported in version v0.22.0.')
+        args.cfg_options = args.options
+
+    return args
+
+
+def main():
+    args = parse_args()
+
+    cfg = Config.fromfile(args.config)
+    if args.cfg_options is not None:
+        cfg.merge_from_dict(args.cfg_options)
+    # set cudnn_benchmark
+    if cfg.get('cudnn_benchmark', False):
+        torch.backends.cudnn.benchmark = True
+
+    # work_dir is determined in this priority: CLI > segment in file > filename
+    if args.work_dir is not None:
+        # update configs according to CLI args if args.work_dir is not None
+        cfg.work_dir = args.work_dir
+    elif cfg.get('work_dir', None) is None:
+        # use config filename as default work_dir if cfg.work_dir is None
+        cfg.work_dir = osp.join('./work_dirs',
+                                osp.splitext(osp.basename(args.config))[0])
+    if args.load_from is not None:
+        cfg.load_from = args.load_from
+    if args.resume_from is not None:
+        cfg.resume_from = args.resume_from
+    if args.gpu_ids is not None:
+        cfg.gpu_ids = args.gpu_ids
+    else:
+        cfg.gpu_ids = range(1) if args.gpus is None else range(args.gpus)
+
+    # init distributed env first, since logger depends on the dist info.
+    if args.launcher == 'none':
+        distributed = False
+    else:
+        distributed = True
+        init_dist(args.launcher, **cfg.dist_params)
+        # gpu_ids is used to calculate iter when resuming checkpoint
+        _, world_size = get_dist_info()
+        cfg.gpu_ids = range(world_size)
+
+    # create work_dir
+    mmcv.mkdir_or_exist(osp.abspath(cfg.work_dir))
+    # dump config
+    cfg.dump(osp.join(cfg.work_dir, osp.basename(args.config)))
+    # init the logger before other steps
+    timestamp = time.strftime('%Y%m%d_%H%M%S', time.localtime())
+    log_file = osp.join(cfg.work_dir, f'{timestamp}.log')
+    logger = get_root_logger(log_file=log_file, log_level=cfg.log_level)
+
+    # init the meta dict to record some important information such as
+    # environment info and seed, which will be logged
+    meta = dict()
+    # log env info
+    env_info_dict = collect_env()
+    env_info = '\n'.join([f'{k}: {v}' for k, v in env_info_dict.items()])
+    dash_line = '-' * 60 + '\n'
+    logger.info('Environment info:\n' + dash_line + env_info + '\n' +
+                dash_line)
+    meta['env_info'] = env_info
+
+    # log some basic info
+    logger.info(f'Distributed training: {distributed}')
+    logger.info(f'Config:\n{cfg.pretty_text}')
+
+    # set random seeds
+    seed = init_random_seed(args.seed)
+    logger.info(f'Set random seed to {seed}, '
+                f'deterministic: {args.deterministic}')
+    set_random_seed(seed, deterministic=args.deterministic)
+    cfg.seed = seed
+    meta['seed'] = seed
+    meta['exp_name'] = osp.basename(args.config)
+
+    model = build_segmentor(
+        cfg.model,
+        train_cfg=cfg.get('train_cfg'),
+        test_cfg=cfg.get('test_cfg'))
+    model.init_weights()
+
+    # SyncBN is not support for DP
+    if not distributed:
+        warnings.warn(
+            'SyncBN is only supported with DDP. To be compatible with DP, '
+            'we convert SyncBN to BN. Please use dist_train.sh which can '
+            'avoid this error.')
+        model = revert_sync_batchnorm(model)
+
+    logger.info(model)
+
+    datasets = [build_dataset(cfg.data.train)]
+    if len(cfg.workflow) == 2:
+        val_dataset = copy.deepcopy(cfg.data.val)
+        val_dataset.pipeline = cfg.data.train.pipeline
+        datasets.append(build_dataset(val_dataset))
+    if cfg.checkpoint_config is not None:
+        # save mmseg version, config file content and class names in
+        # checkpoints as meta data
+        cfg.checkpoint_config.meta = dict(
+            mmseg_version=f'{__version__}+{get_git_hash()[:7]}',
+            config=cfg.pretty_text,
+            CLASSES=datasets[0].CLASSES,
+            PALETTE=datasets[0].PALETTE)
+    # add an attribute for visualization convenience
+    model.CLASSES = datasets[0].CLASSES
+    # passing checkpoint meta for saving best checkpoint
+    meta.update(cfg.checkpoint_config.meta)
+    train_segmentor(
+        model,
+        datasets,
+        cfg,
+        distributed=distributed,
+        validate=(not args.no_validate),
+        timestamp=timestamp,
+        meta=meta)
+
+
+if __name__ == '__main__':
+    main()