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# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
from __future__ import absolute_import, division, print_function, unicode_literals
import numpy as np
import unittest
import torch
from torchvision import ops
from detectron2.layers import batched_nms, batched_nms_rotated, nms_rotated
def nms_edit_distance(keep1, keep2):
"""
Compare the "keep" result of two nms call.
They are allowed to be different in terms of edit distance
due to floating point precision issues, e.g.,
if a box happen to have an IoU of 0.5 with another box,
one implentation may choose to keep it while another may discard it.
"""
if torch.equal(keep1, keep2):
# they should be equal most of the time
return 0
keep1, keep2 = tuple(keep1.cpu()), tuple(keep2.cpu())
m, n = len(keep1), len(keep2)
# edit distance with DP
f = [np.arange(n + 1), np.arange(n + 1)]
for i in range(m):
cur_row = i % 2
other_row = (i + 1) % 2
f[other_row][0] = i + 1
for j in range(n):
f[other_row][j + 1] = (
f[cur_row][j]
if keep1[i] == keep2[j]
else min(min(f[cur_row][j], f[cur_row][j + 1]), f[other_row][j]) + 1
)
return f[m % 2][n]
class TestNMSRotated(unittest.TestCase):
def reference_horizontal_nms(self, boxes, scores, iou_threshold):
"""
Args:
box_scores (N, 5): boxes in corner-form and probabilities.
(Note here 5 == 4 + 1, i.e., 4-dim horizontal box + 1-dim prob)
iou_threshold: intersection over union threshold.
Returns:
picked: a list of indexes of the kept boxes
"""
picked = []
_, indexes = scores.sort(descending=True)
while len(indexes) > 0:
current = indexes[0]
picked.append(current.item())
if len(indexes) == 1:
break
current_box = boxes[current, :]
indexes = indexes[1:]
rest_boxes = boxes[indexes, :]
iou = ops.box_iou(rest_boxes, current_box.unsqueeze(0)).squeeze(1)
indexes = indexes[iou <= iou_threshold]
return torch.as_tensor(picked)
def _create_tensors(self, N):
boxes = torch.rand(N, 4) * 100
# Note: the implementation of this function in torchvision is:
# boxes[:, 2:] += torch.rand(N, 2) * 100
# but it does not guarantee non-negative widths/heights constraints:
# boxes[:, 2] >= boxes[:, 0] and boxes[:, 3] >= boxes[:, 1]:
boxes[:, 2:] += boxes[:, :2]
scores = torch.rand(N)
return boxes, scores
def test_batched_nms_rotated_0_degree_cpu(self):
N = 2000
num_classes = 50
boxes, scores = self._create_tensors(N)
idxs = torch.randint(0, num_classes, (N,))
rotated_boxes = torch.zeros(N, 5)
rotated_boxes[:, 0] = (boxes[:, 0] + boxes[:, 2]) / 2.0
rotated_boxes[:, 1] = (boxes[:, 1] + boxes[:, 3]) / 2.0
rotated_boxes[:, 2] = boxes[:, 2] - boxes[:, 0]
rotated_boxes[:, 3] = boxes[:, 3] - boxes[:, 1]
err_msg = "Rotated NMS with 0 degree is incompatible with horizontal NMS for IoU={}"
for iou in [0.2, 0.5, 0.8]:
backup = boxes.clone()
keep_ref = batched_nms(boxes, scores, idxs, iou)
assert torch.allclose(boxes, backup), "boxes modified by batched_nms"
backup = rotated_boxes.clone()
keep = batched_nms_rotated(rotated_boxes, scores, idxs, iou)
assert torch.allclose(
rotated_boxes, backup
), "rotated_boxes modified by batched_nms_rotated"
self.assertLessEqual(nms_edit_distance(keep, keep_ref), 1, err_msg.format(iou))
@unittest.skipIf(not torch.cuda.is_available(), "CUDA not available")
def test_batched_nms_rotated_0_degree_cuda(self):
N = 2000
num_classes = 50
boxes, scores = self._create_tensors(N)
idxs = torch.randint(0, num_classes, (N,))
rotated_boxes = torch.zeros(N, 5)
rotated_boxes[:, 0] = (boxes[:, 0] + boxes[:, 2]) / 2.0
rotated_boxes[:, 1] = (boxes[:, 1] + boxes[:, 3]) / 2.0
rotated_boxes[:, 2] = boxes[:, 2] - boxes[:, 0]
rotated_boxes[:, 3] = boxes[:, 3] - boxes[:, 1]
err_msg = "Rotated NMS with 0 degree is incompatible with horizontal NMS for IoU={}"
for iou in [0.2, 0.5, 0.8]:
backup = boxes.clone()
keep_ref = batched_nms(boxes.cuda(), scores.cuda(), idxs, iou)
self.assertTrue(torch.allclose(boxes, backup), "boxes modified by batched_nms")
backup = rotated_boxes.clone()
keep = batched_nms_rotated(rotated_boxes.cuda(), scores.cuda(), idxs, iou)
self.assertTrue(
torch.allclose(rotated_boxes, backup),
"rotated_boxes modified by batched_nms_rotated",
)
self.assertLessEqual(nms_edit_distance(keep, keep_ref), 1, err_msg.format(iou))
def test_nms_rotated_0_degree_cpu(self):
N = 1000
boxes, scores = self._create_tensors(N)
rotated_boxes = torch.zeros(N, 5)
rotated_boxes[:, 0] = (boxes[:, 0] + boxes[:, 2]) / 2.0
rotated_boxes[:, 1] = (boxes[:, 1] + boxes[:, 3]) / 2.0
rotated_boxes[:, 2] = boxes[:, 2] - boxes[:, 0]
rotated_boxes[:, 3] = boxes[:, 3] - boxes[:, 1]
err_msg = "Rotated NMS incompatible between CPU and reference implementation for IoU={}"
for iou in [0.5]:
keep_ref = self.reference_horizontal_nms(boxes, scores, iou)
keep = nms_rotated(rotated_boxes, scores, iou)
self.assertLessEqual(nms_edit_distance(keep, keep_ref), 1, err_msg.format(iou))
def test_nms_rotated_90_degrees_cpu(self):
N = 1000
boxes, scores = self._create_tensors(N)
rotated_boxes = torch.zeros(N, 5)
rotated_boxes[:, 0] = (boxes[:, 0] + boxes[:, 2]) / 2.0
rotated_boxes[:, 1] = (boxes[:, 1] + boxes[:, 3]) / 2.0
# Note for rotated_boxes[:, 2] and rotated_boxes[:, 3]:
# widths and heights are intentionally swapped here for 90 degrees case
# so that the reference horizontal nms could be used
rotated_boxes[:, 2] = boxes[:, 3] - boxes[:, 1]
rotated_boxes[:, 3] = boxes[:, 2] - boxes[:, 0]
rotated_boxes[:, 4] = torch.ones(N) * 90
err_msg = "Rotated NMS incompatible between CPU and reference implementation for IoU={}"
for iou in [0.2, 0.5, 0.8]:
keep_ref = self.reference_horizontal_nms(boxes, scores, iou)
keep = nms_rotated(rotated_boxes, scores, iou)
assert torch.equal(keep, keep_ref), err_msg.format(iou)
def test_nms_rotated_180_degrees_cpu(self):
N = 1000
boxes, scores = self._create_tensors(N)
rotated_boxes = torch.zeros(N, 5)
rotated_boxes[:, 0] = (boxes[:, 0] + boxes[:, 2]) / 2.0
rotated_boxes[:, 1] = (boxes[:, 1] + boxes[:, 3]) / 2.0
rotated_boxes[:, 2] = boxes[:, 2] - boxes[:, 0]
rotated_boxes[:, 3] = boxes[:, 3] - boxes[:, 1]
rotated_boxes[:, 4] = torch.ones(N) * 180
err_msg = "Rotated NMS incompatible between CPU and reference implementation for IoU={}"
for iou in [0.2, 0.5, 0.8]:
keep_ref = self.reference_horizontal_nms(boxes, scores, iou)
keep = nms_rotated(rotated_boxes, scores, iou)
assert torch.equal(keep, keep_ref), err_msg.format(iou)
@unittest.skipIf(not torch.cuda.is_available(), "CUDA not available")
def test_nms_rotated_0_degree_cuda(self):
N = 1000
boxes, scores = self._create_tensors(N)
rotated_boxes = torch.zeros(N, 5)
rotated_boxes[:, 0] = (boxes[:, 0] + boxes[:, 2]) / 2.0
rotated_boxes[:, 1] = (boxes[:, 1] + boxes[:, 3]) / 2.0
rotated_boxes[:, 2] = boxes[:, 2] - boxes[:, 0]
rotated_boxes[:, 3] = boxes[:, 3] - boxes[:, 1]
err_msg = "Rotated NMS incompatible between CPU and CUDA for IoU={}"
for iou in [0.2, 0.5, 0.8]:
r_cpu = nms_rotated(rotated_boxes, scores, iou)
r_cuda = nms_rotated(rotated_boxes.cuda(), scores.cuda(), iou)
assert torch.equal(r_cpu, r_cuda.cpu()), err_msg.format(iou)
if __name__ == "__main__":
unittest.main()