[Fix] Fix bugs in DynamicScatter op (#1748)

* Fix bugs in DynamicScatter op

* recover unittest

* add a comment as a reminder

* compatible to torch with lower version

mmcv/ops/csrc/pytorch/cuda/scatter_points_cuda.cu

@@ -26,10 +26,15 @@ std::vector<at::Tensor> DynamicPointToVoxelForwardCUDAKernelLauncher(
   std::tie(out_coors, coors_map, reduce_count) =
       at::unique_dim(coors_clean, 0, true, true, true);
 
-  // the first element of out_coors is always (-1,-1,-1) and should be removed
+  if (out_coors[0][0].lt(0).item<bool>()) {
+    // the first element of out_coors (-1,-1,-1) and should be removed
     out_coors = out_coors.slice(0, 1);
-  reduce_count = reduce_count.slice(0, 1).to(torch::kInt32);
-  coors_map = coors_map.to(torch::kInt32) - 1;
+    reduce_count = reduce_count.slice(0, 1);
+    coors_map = coors_map - 1;
+  }
+
+  coors_map = coors_map.to(torch::kInt32);
+  reduce_count = reduce_count.to(torch::kInt32);
 
   auto reduced_feats =
       at::empty({out_coors.size(0), num_feats}, feats.options());

tests/test_ops/test_scatter_points.py

@@ -76,6 +76,42 @@ def test_dynamic_scatter():
     feats_out_max = feats_out_max[seq_max]
     coors_cout_max = coors_out_max[seq_max]
 
+    assert (coors_out_mean == ref_voxel_coors).all()
+    assert torch.allclose(
+        feats_out_mean, ref_voxel_feats_mean, atol=1e-2, rtol=1e-5)
+    assert (coors_cout_max == ref_voxel_coors).all()
+    assert torch.allclose(
+        feats_out_max, ref_voxel_feats_max, atol=1e-2, rtol=1e-5)
+
+    # test non-empty input without any point out of bound
+    feats = torch.rand(
+        size=(200000, 3), dtype=torch.float32, device='cuda') * 100 - 50
+    coors = torch.randint(
+        low=0, high=20, size=(200000, 3), dtype=torch.int32, device='cuda')
+
+    ref_voxel_coors = coors.unique(dim=0, sorted=True)
+    ref_voxel_coors = ref_voxel_coors[ref_voxel_coors.min(dim=-1).values >= 0]
+    ref_voxel_feats_mean = []
+    ref_voxel_feats_max = []
+    for ref_voxel_coor in ref_voxel_coors:
+        voxel_mask = (coors == ref_voxel_coor).all(dim=-1)
+        ref_voxel_feats_mean.append(feats[voxel_mask].mean(dim=0))
+        ref_voxel_feats_max.append(feats[voxel_mask].max(dim=0).values)
+    ref_voxel_feats_mean = torch.stack(ref_voxel_feats_mean)
+    ref_voxel_feats_max = torch.stack(ref_voxel_feats_max)
+
+    feats_out_mean, coors_out_mean = dsmean(feats, coors)
+    seq_mean = (coors_out_mean[:, 0] * 400 + coors_out_mean[:, 1] * 20 +
+                coors_out_mean[:, 2]).argsort()
+    feats_out_mean = feats_out_mean[seq_mean]
+    coors_out_mean = coors_out_mean[seq_mean]
+
+    feats_out_max, coors_out_max = dsmax(feats, coors)
+    seq_max = (coors_out_max[:, 0] * 400 + coors_out_max[:, 1] * 20 +
+               coors_out_max[:, 2]).argsort()
+    feats_out_max = feats_out_max[seq_max]
+    coors_cout_max = coors_out_max[seq_max]
+
     assert (coors_out_mean == ref_voxel_coors).all()
     assert torch.allclose(
         feats_out_mean, ref_voxel_feats_mean, atol=1e-2, rtol=1e-5)