diff --git a/pcdet/utils/common_utils.py b/pcdet/utils/common_utils.py
new file mode 100644
index 0000000..af70728
--- /dev/null
+++ b/pcdet/utils/common_utils.py
@@ -0,0 +1,295 @@
+import logging
+import os
+import pickle
+import random
+import shutil
+import subprocess
+import SharedArray
+
+import numpy as np
+import torch
+import torch.distributed as dist
+import torch.multiprocessing as mp
+
+
+def check_numpy_to_torch(x):
+    if isinstance(x, np.ndarray):
+        return torch.from_numpy(x).float(), True
+    return x, False
+
+
+def limit_period(val, offset=0.5, period=np.pi):
+    val, is_numpy = check_numpy_to_torch(val)
+    ans = val - torch.floor(val / period + offset) * period
+    return ans.numpy() if is_numpy else ans
+
+
+def drop_info_with_name(info, name):
+    ret_info = {}
+    keep_indices = [i for i, x in enumerate(info['name']) if x != name]
+    for key in info.keys():
+        ret_info[key] = info[key][keep_indices]
+    return ret_info
+
+
+def rotate_points_along_z(points, angle):
+    """
+    Args:
+        points: (B, N, 3 + C)
+        angle: (B), angle along z-axis, angle increases x ==> y
+    Returns:
+
+    """
+    points, is_numpy = check_numpy_to_torch(points)
+    angle, _ = check_numpy_to_torch(angle)
+
+    cosa = torch.cos(angle)
+    sina = torch.sin(angle)
+    zeros = angle.new_zeros(points.shape[0])
+    ones = angle.new_ones(points.shape[0])
+    rot_matrix = torch.stack((
+        cosa,  sina, zeros,
+        -sina, cosa, zeros,
+        zeros, zeros, ones
+    ), dim=1).view(-1, 3, 3).float()
+    points_rot = torch.matmul(points[:, :, 0:3], rot_matrix)
+    points_rot = torch.cat((points_rot, points[:, :, 3:]), dim=-1)
+    return points_rot.numpy() if is_numpy else points_rot
+
+
+def angle2matrix(angle):
+    """
+    Args:
+        angle: angle along z-axis, angle increases x ==> y
+    Returns:
+        rot_matrix: (3x3 Tensor) rotation matrix
+    """
+
+    cosa = torch.cos(angle)
+    sina = torch.sin(angle)
+    rot_matrix = torch.tensor([
+        [cosa, -sina, 0],
+        [sina, cosa,  0],
+        [   0,    0,  1]
+    ])
+    return rot_matrix
+
+
+def mask_points_by_range(points, limit_range):
+    mask = (points[:, 0] >= limit_range[0]) & (points[:, 0] <= limit_range[3]) \
+           & (points[:, 1] >= limit_range[1]) & (points[:, 1] <= limit_range[4])
+    return mask
+
+
+def get_voxel_centers(voxel_coords, downsample_times, voxel_size, point_cloud_range):
+    """
+    Args:
+        voxel_coords: (N, 3)
+        downsample_times:
+        voxel_size:
+        point_cloud_range:
+
+    Returns:
+
+    """
+    assert voxel_coords.shape[1] == 3
+    voxel_centers = voxel_coords[:, [2, 1, 0]].float()  # (xyz)
+    voxel_size = torch.tensor(voxel_size, device=voxel_centers.device).float() * downsample_times
+    pc_range = torch.tensor(point_cloud_range[0:3], device=voxel_centers.device).float()
+    voxel_centers = (voxel_centers + 0.5) * voxel_size + pc_range
+    return voxel_centers
+
+
+def create_logger(log_file=None, rank=0, log_level=logging.INFO):
+    logger = logging.getLogger(__name__)
+    logger.setLevel(log_level if rank == 0 else 'ERROR')
+    formatter = logging.Formatter('%(asctime)s  %(levelname)5s  %(message)s')
+    console = logging.StreamHandler()
+    console.setLevel(log_level if rank == 0 else 'ERROR')
+    console.setFormatter(formatter)
+    logger.addHandler(console)
+    if log_file is not None:
+        file_handler = logging.FileHandler(filename=log_file)
+        file_handler.setLevel(log_level if rank == 0 else 'ERROR')
+        file_handler.setFormatter(formatter)
+        logger.addHandler(file_handler)
+    logger.propagate = False
+    return logger
+
+
+def set_random_seed(seed):
+    random.seed(seed)
+    np.random.seed(seed)
+    torch.manual_seed(seed)
+    torch.cuda.manual_seed(seed)
+    torch.backends.cudnn.deterministic = True
+    torch.backends.cudnn.benchmark = False
+
+
+def worker_init_fn(worker_id, seed=666):
+    if seed is not None:
+        random.seed(seed + worker_id)
+        np.random.seed(seed + worker_id)
+        torch.manual_seed(seed + worker_id)
+        torch.cuda.manual_seed(seed + worker_id)
+        torch.cuda.manual_seed_all(seed + worker_id)
+
+
+def get_pad_params(desired_size, cur_size):
+    """
+    Get padding parameters for np.pad function
+    Args:
+        desired_size: int, Desired padded output size
+        cur_size: int, Current size. Should always be less than or equal to cur_size
+    Returns:
+        pad_params: tuple(int), Number of values padded to the edges (before, after)
+    """
+    assert desired_size >= cur_size
+
+    # Calculate amount to pad
+    diff = desired_size - cur_size
+    pad_params = (0, diff)
+
+    return pad_params
+
+
+def keep_arrays_by_name(gt_names, used_classes):
+    inds = [i for i, x in enumerate(gt_names) if x in used_classes]
+    inds = np.array(inds, dtype=np.int64)
+    return inds
+
+
+def init_dist_slurm(tcp_port, local_rank, backend='nccl'):
+    """
+    modified from https://github.com/open-mmlab/mmdetection
+    Args:
+        tcp_port:
+        backend:
+
+    Returns:
+
+    """
+    proc_id = int(os.environ['SLURM_PROCID'])
+    ntasks = int(os.environ['SLURM_NTASKS'])
+    node_list = os.environ['SLURM_NODELIST']
+    num_gpus = torch.cuda.device_count()
+    torch.cuda.set_device(proc_id % num_gpus)
+    addr = subprocess.getoutput('scontrol show hostname {} | head -n1'.format(node_list))
+    os.environ['MASTER_PORT'] = str(tcp_port)
+    os.environ['MASTER_ADDR'] = addr
+    os.environ['WORLD_SIZE'] = str(ntasks)
+    os.environ['RANK'] = str(proc_id)
+    dist.init_process_group(backend=backend)
+
+    total_gpus = dist.get_world_size()
+    rank = dist.get_rank()
+    return total_gpus, rank
+
+
+def init_dist_pytorch(tcp_port, local_rank, backend='nccl'):
+    if mp.get_start_method(allow_none=True) is None:
+        mp.set_start_method('spawn')
+    # os.environ['MASTER_PORT'] = str(tcp_port)
+    # os.environ['MASTER_ADDR'] = 'localhost'
+    num_gpus = torch.cuda.device_count()
+    torch.cuda.set_device(local_rank % num_gpus)
+
+    dist.init_process_group(
+        backend=backend,
+        # init_method='tcp://127.0.0.1:%d' % tcp_port,
+        # rank=local_rank,
+        # world_size=num_gpus
+    )
+    rank = dist.get_rank()
+    return num_gpus, rank
+
+
+def get_dist_info(return_gpu_per_machine=False):
+    if torch.__version__ < '1.0':
+        initialized = dist._initialized
+    else:
+        if dist.is_available():
+            initialized = dist.is_initialized()
+        else:
+            initialized = False
+    if initialized:
+        rank = dist.get_rank()
+        world_size = dist.get_world_size()
+    else:
+        rank = 0
+        world_size = 1
+
+    if return_gpu_per_machine:
+        gpu_per_machine = torch.cuda.device_count()
+        return rank, world_size, gpu_per_machine
+
+    return rank, world_size
+
+
+def merge_results_dist(result_part, size, tmpdir):
+    rank, world_size = get_dist_info()
+    os.makedirs(tmpdir, exist_ok=True)
+
+    dist.barrier()
+    pickle.dump(result_part, open(os.path.join(tmpdir, 'result_part_{}.pkl'.format(rank)), 'wb'))
+    dist.barrier()
+
+    if rank != 0:
+        return None
+
+    part_list = []
+    for i in range(world_size):
+        part_file = os.path.join(tmpdir, 'result_part_{}.pkl'.format(i))
+        part_list.append(pickle.load(open(part_file, 'rb')))
+
+    ordered_results = []
+    for res in zip(*part_list):
+        ordered_results.extend(list(res))
+    ordered_results = ordered_results[:size]
+    shutil.rmtree(tmpdir)
+    return ordered_results
+
+
+def scatter_point_inds(indices, point_inds, shape):
+    ret = -1 * torch.ones(*shape, dtype=point_inds.dtype, device=point_inds.device)
+    ndim = indices.shape[-1]
+    flattened_indices = indices.view(-1, ndim)
+    slices = [flattened_indices[:, i] for i in range(ndim)]
+    ret[slices] = point_inds
+    return ret
+
+
+def generate_voxel2pinds(sparse_tensor):
+    device = sparse_tensor.indices.device
+    batch_size = sparse_tensor.batch_size
+    spatial_shape = sparse_tensor.spatial_shape
+    indices = sparse_tensor.indices.long()
+    point_indices = torch.arange(indices.shape[0], device=device, dtype=torch.int32)
+    output_shape = [batch_size] + list(spatial_shape)
+    v2pinds_tensor = scatter_point_inds(indices, point_indices, output_shape)
+    return v2pinds_tensor
+
+
+def sa_create(name, var):
+    x = SharedArray.create(name, var.shape, dtype=var.dtype)
+    x[...] = var[...]
+    x.flags.writeable = False
+    return x
+
+
+class AverageMeter(object):
+    """Computes and stores the average and current value"""
+    def __init__(self):
+        self.reset()
+
+    def reset(self):
+        self.val = 0
+        self.avg = 0
+        self.sum = 0
+        self.count = 0
+
+    def update(self, val, n=1):
+        self.val = val
+        self.sum += val * n
+        self.count += n
+        self.avg = self.sum / self.count