diff --git a/pcdet/ops/iou3d_nms/iou3d_nms_utils.py b/pcdet/ops/iou3d_nms/iou3d_nms_utils.py
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+++ b/pcdet/ops/iou3d_nms/iou3d_nms_utils.py
@@ -0,0 +1,189 @@
+"""
+3D IoU Calculation and Rotated NMS
+Written by Shaoshuai Shi
+All Rights Reserved 2019-2020.
+"""
+import torch
+
+from ...utils import common_utils
+from . import iou3d_nms_cuda
+
+
+def boxes_bev_iou_cpu(boxes_a, boxes_b):
+    """
+    Args:
+        boxes_a: (N, 7) [x, y, z, dx, dy, dz, heading]
+        boxes_b: (M, 7) [x, y, z, dx, dy, dz, heading]
+
+    Returns:
+        ans_iou: (N, M)
+    """
+    boxes_a, is_numpy = common_utils.check_numpy_to_torch(boxes_a)
+    boxes_b, is_numpy = common_utils.check_numpy_to_torch(boxes_b)
+    assert not (boxes_a.is_cuda or boxes_b.is_cuda), 'Only support CPU tensors'
+    assert boxes_a.shape[1] == 7 and boxes_b.shape[1] == 7
+    ans_iou = boxes_a.new_zeros(torch.Size((boxes_a.shape[0], boxes_b.shape[0])))
+    iou3d_nms_cuda.boxes_iou_bev_cpu(boxes_a.contiguous(), boxes_b.contiguous(), ans_iou)
+
+    return ans_iou.numpy() if is_numpy else ans_iou
+
+
+def boxes_iou_bev(boxes_a, boxes_b):
+    """
+    Args:
+        boxes_a: (N, 7) [x, y, z, dx, dy, dz, heading]
+        boxes_b: (M, 7) [x, y, z, dx, dy, dz, heading]
+
+    Returns:
+        ans_iou: (N, M)
+    """
+    assert boxes_a.shape[1] == boxes_b.shape[1] == 7
+    ans_iou = torch.cuda.FloatTensor(torch.Size((boxes_a.shape[0], boxes_b.shape[0]))).zero_()
+
+    iou3d_nms_cuda.boxes_iou_bev_gpu(boxes_a.contiguous(), boxes_b.contiguous(), ans_iou)
+
+    return ans_iou
+
+
+def boxes_iou3d_gpu(boxes_a, boxes_b):
+    """
+    Args:
+        boxes_a: (N, 7) [x, y, z, dx, dy, dz, heading]
+        boxes_b: (M, 7) [x, y, z, dx, dy, dz, heading]
+
+    Returns:
+        ans_iou: (N, M)
+    """
+    assert boxes_a.shape[1] == boxes_b.shape[1] == 7
+
+    # height overlap
+    boxes_a_height_max = (boxes_a[:, 2] + boxes_a[:, 5] / 2).view(-1, 1)
+    boxes_a_height_min = (boxes_a[:, 2] - boxes_a[:, 5] / 2).view(-1, 1)
+    boxes_b_height_max = (boxes_b[:, 2] + boxes_b[:, 5] / 2).view(1, -1)
+    boxes_b_height_min = (boxes_b[:, 2] - boxes_b[:, 5] / 2).view(1, -1)
+
+    # bev overlap
+    overlaps_bev = torch.cuda.FloatTensor(torch.Size((boxes_a.shape[0], boxes_b.shape[0]))).zero_()  # (N, M)
+    iou3d_nms_cuda.boxes_overlap_bev_gpu(boxes_a.contiguous(), boxes_b.contiguous(), overlaps_bev)
+
+    max_of_min = torch.max(boxes_a_height_min, boxes_b_height_min)
+    min_of_max = torch.min(boxes_a_height_max, boxes_b_height_max)
+    overlaps_h = torch.clamp(min_of_max - max_of_min, min=0)
+
+    # 3d iou
+    overlaps_3d = overlaps_bev * overlaps_h
+
+    vol_a = (boxes_a[:, 3] * boxes_a[:, 4] * boxes_a[:, 5]).view(-1, 1)
+    vol_b = (boxes_b[:, 3] * boxes_b[:, 4] * boxes_b[:, 5]).view(1, -1)
+
+    iou3d = overlaps_3d / torch.clamp(vol_a + vol_b - overlaps_3d, min=1e-6)
+
+    return iou3d
+
+def boxes_aligned_iou3d_gpu(boxes_a, boxes_b):
+    """
+    Args:
+        boxes_a: (N, 7) [x, y, z, dx, dy, dz, heading]
+        boxes_b: (N, 7) [x, y, z, dx, dy, dz, heading]
+
+    Returns:
+        ans_iou: (N,)
+    """
+    assert boxes_a.shape[0] == boxes_b.shape[0]
+    assert boxes_a.shape[1] == boxes_b.shape[1] == 7
+
+    # height overlap
+    boxes_a_height_max = (boxes_a[:, 2] + boxes_a[:, 5] / 2).view(-1, 1)
+    boxes_a_height_min = (boxes_a[:, 2] - boxes_a[:, 5] / 2).view(-1, 1)
+    boxes_b_height_max = (boxes_b[:, 2] + boxes_b[:, 5] / 2).view(-1, 1)
+    boxes_b_height_min = (boxes_b[:, 2] - boxes_b[:, 5] / 2).view(-1, 1)
+
+    # bev overlap
+    overlaps_bev = torch.cuda.FloatTensor(torch.Size((boxes_a.shape[0], 1))).zero_()  # (N, M)
+    iou3d_nms_cuda.boxes_aligned_overlap_bev_gpu(boxes_a.contiguous(), boxes_b.contiguous(), overlaps_bev)
+
+    max_of_min = torch.max(boxes_a_height_min, boxes_b_height_min)
+    min_of_max = torch.min(boxes_a_height_max, boxes_b_height_max)
+    overlaps_h = torch.clamp(min_of_max - max_of_min, min=0)
+
+    # 3d iou
+    overlaps_3d = overlaps_bev * overlaps_h
+
+    vol_a = (boxes_a[:, 3] * boxes_a[:, 4] * boxes_a[:, 5]).view(-1, 1)
+    vol_b = (boxes_b[:, 3] * boxes_b[:, 4] * boxes_b[:, 5]).view(-1, 1)
+
+    iou3d = overlaps_3d / torch.clamp(vol_a + vol_b - overlaps_3d, min=1e-6)
+
+    return iou3d
+
+
+def nms_gpu(boxes, scores, thresh, pre_maxsize=None, **kwargs):
+    """
+    :param boxes: (N, 7) [x, y, z, dx, dy, dz, heading]
+    :param scores: (N)
+    :param thresh:
+    :return:
+    """
+    assert boxes.shape[1] == 7
+    order = scores.sort(0, descending=True)[1]
+    if pre_maxsize is not None:
+        order = order[:pre_maxsize]
+
+    boxes = boxes[order].contiguous()
+    keep = torch.LongTensor(boxes.size(0))
+    num_out = iou3d_nms_cuda.nms_gpu(boxes, keep, thresh)
+    return order[keep[:num_out].cuda()].contiguous(), None
+
+
+def nms_normal_gpu(boxes, scores, thresh, **kwargs):
+    """
+    :param boxes: (N, 7) [x, y, z, dx, dy, dz, heading]
+    :param scores: (N)
+    :param thresh:
+    :return:
+    """
+    assert boxes.shape[1] == 7
+    order = scores.sort(0, descending=True)[1]
+
+    boxes = boxes[order].contiguous()
+
+    keep = torch.LongTensor(boxes.size(0))
+    num_out = iou3d_nms_cuda.nms_normal_gpu(boxes, keep, thresh)
+    return order[keep[:num_out].cuda()].contiguous(), None
+
+
+def paired_boxes_iou3d_gpu(boxes_a, boxes_b):
+    """
+    Args:
+        boxes_a: (N, 7) [x, y, z, dx, dy, dz, heading]
+        boxes_b: (N, 7) [x, y, z, dx, dy, dz, heading]
+
+    Returns:
+        ans_iou: (N)
+    """
+    assert boxes_a.shape[0] == boxes_b.shape[0]
+    assert boxes_a.shape[1] == boxes_b.shape[1] == 7
+
+    # height overlap
+    boxes_a_height_max = (boxes_a[:, 2] + boxes_a[:, 5] / 2).view(-1, 1)
+    boxes_a_height_min = (boxes_a[:, 2] - boxes_a[:, 5] / 2).view(-1, 1)
+    boxes_b_height_max = (boxes_b[:, 2] + boxes_b[:, 5] / 2).view(-1, 1)
+    boxes_b_height_min = (boxes_b[:, 2] - boxes_b[:, 5] / 2).view(-1, 1)
+
+    # bev overlap
+    overlaps_bev = torch.cuda.FloatTensor(torch.Size((boxes_a.shape[0], 1))).zero_()  # (N, ``)
+    iou3d_nms_cuda.paired_boxes_overlap_bev_gpu(boxes_a.contiguous(), boxes_b.contiguous(), overlaps_bev)
+
+    max_of_min = torch.max(boxes_a_height_min, boxes_b_height_min)
+    min_of_max = torch.min(boxes_a_height_max, boxes_b_height_max)
+    overlaps_h = torch.clamp(min_of_max - max_of_min, min=0)
+
+    # 3d iou
+    overlaps_3d = overlaps_bev * overlaps_h
+
+    vol_a = (boxes_a[:, 3] * boxes_a[:, 4] * boxes_a[:, 5]).view(-1, 1)
+    vol_b = (boxes_b[:, 3] * boxes_b[:, 4] * boxes_b[:, 5]).view(-1, 1)
+
+    iou3d = overlaps_3d / torch.clamp(vol_a + vol_b - overlaps_3d, min=1e-6)
+
+    return iou3d.view(-1)
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