[ONNX] Support exporting RoiAlign align=True to ONNX with opset 16 (#6685)

* Support exporting RoiAlign align=True to ONNX with opset 16

* lint: ufmt
Co-authored-by: Vasilis Vryniotis <datumbox@users.noreply.github.com>

test/test_onnx.py

 import io
 from collections import OrderedDict
-from typing import List, Tuple
+from typing import List, Optional, Tuple
 
 import pytest
 import torch
@@ -11,7 +11,7 @@ from torchvision.models.detection.image_list import ImageList
 from torchvision.models.detection.roi_heads import RoIHeads
 from torchvision.models.detection.rpn import AnchorGenerator, RegionProposalNetwork, RPNHead
 from torchvision.models.detection.transform import GeneralizedRCNNTransform
-from torchvision.ops._register_onnx_ops import _onnx_opset_version
+from torchvision.ops import _register_onnx_ops
 
 # In environments without onnxruntime we prefer to
 # invoke all tests in the repo and have this one skipped rather than fail.
@@ -32,7 +32,11 @@ class TestONNXExporter:
         dynamic_axes=None,
         output_names=None,
         input_names=None,
+        opset_version: Optional[int] = None,
     ):
+        if opset_version is None:
+            opset_version = _register_onnx_ops.base_onnx_opset_version
+
         model.eval()
 
         onnx_io = io.BytesIO()
@@ -46,10 +50,11 @@ class TestONNXExporter:
             torch_onnx_input,
             onnx_io,
             do_constant_folding=do_constant_folding,
-            opset_version=_onnx_opset_version,
+            opset_version=opset_version,
             dynamic_axes=dynamic_axes,
             input_names=input_names,
             output_names=output_names,
+            verbose=True,
         )
         # validate the exported model with onnx runtime
         for test_inputs in inputs_list:
@@ -140,39 +145,39 @@ class TestONNXExporter:
         model = ops.RoIAlign((5, 5), 1, -1)
         self.run_model(model, [(x, single_roi)])
 
-    @pytest.mark.skip(reason="ROIAlign with aligned=True is not supported in ONNX, but will be supported in opset 16.")
     def test_roi_align_aligned(self):
+        supported_onnx_version = _register_onnx_ops._onnx_opset_version_16
         x = torch.rand(1, 1, 10, 10, dtype=torch.float32)
         single_roi = torch.tensor([[0, 1.5, 1.5, 3, 3]], dtype=torch.float32)
         model = ops.RoIAlign((5, 5), 1, 2, aligned=True)
-        self.run_model(model, [(x, single_roi)])
+        self.run_model(model, [(x, single_roi)], opset_version=supported_onnx_version)
 
         x = torch.rand(1, 1, 10, 10, dtype=torch.float32)
         single_roi = torch.tensor([[0, 0.2, 0.3, 4.5, 3.5]], dtype=torch.float32)
         model = ops.RoIAlign((5, 5), 0.5, 3, aligned=True)
-        self.run_model(model, [(x, single_roi)])
+        self.run_model(model, [(x, single_roi)], opset_version=supported_onnx_version)
 
         x = torch.rand(1, 1, 10, 10, dtype=torch.float32)
         single_roi = torch.tensor([[0, 0.2, 0.3, 4.5, 3.5]], dtype=torch.float32)
         model = ops.RoIAlign((5, 5), 1.8, 2, aligned=True)
-        self.run_model(model, [(x, single_roi)])
+        self.run_model(model, [(x, single_roi)], opset_version=supported_onnx_version)
 
         x = torch.rand(1, 1, 10, 10, dtype=torch.float32)
         single_roi = torch.tensor([[0, 0.2, 0.3, 4.5, 3.5]], dtype=torch.float32)
         model = ops.RoIAlign((2, 2), 2.5, 0, aligned=True)
-        self.run_model(model, [(x, single_roi)])
+        self.run_model(model, [(x, single_roi)], opset_version=supported_onnx_version)
 
         x = torch.rand(1, 1, 10, 10, dtype=torch.float32)
         single_roi = torch.tensor([[0, 0.2, 0.3, 4.5, 3.5]], dtype=torch.float32)
         model = ops.RoIAlign((2, 2), 2.5, -1, aligned=True)
-        self.run_model(model, [(x, single_roi)])
+        self.run_model(model, [(x, single_roi)], opset_version=supported_onnx_version)
 
-    @pytest.mark.skip(reason="Issue in exporting ROIAlign with aligned = True for malformed boxes")
     def test_roi_align_malformed_boxes(self):
+        supported_onnx_version = _register_onnx_ops._onnx_opset_version_16
         x = torch.randn(1, 1, 10, 10, dtype=torch.float32)
         single_roi = torch.tensor([[0, 2, 0.3, 1.5, 1.5]], dtype=torch.float32)
         model = ops.RoIAlign((5, 5), 1, 1, aligned=True)
-        self.run_model(model, [(x, single_roi)])
+        self.run_model(model, [(x, single_roi)], opset_version=supported_onnx_version)
 
     def test_roi_pool(self):
         x = torch.rand(1, 1, 10, 10, dtype=torch.float32)

torchvision/ops/_register_onnx_ops.py

@@ -3,7 +3,9 @@ import warnings
 
 import torch
 
-_onnx_opset_version = 11
+_onnx_opset_version_11 = 11
+_onnx_opset_version_16 = 16
+base_onnx_opset_version = _onnx_opset_version_11
 
 
 def _register_custom_op():
@@ -20,32 +22,56 @@ def _register_custom_op():
         nms_out = g.op("NonMaxSuppression", boxes, scores, max_output_per_class, iou_threshold)
         return squeeze(g, select(g, nms_out, 1, g.op("Constant", value_t=torch.tensor([2], dtype=torch.long))), 1)
 
-    @parse_args("v", "v", "f", "i", "i", "i", "i")
-    def roi_align(g, input, rois, spatial_scale, pooled_height, pooled_width, sampling_ratio, aligned):
-        batch_indices = _cast_Long(
+    def _process_batch_indices_for_roi_align(g, rois):
+        return _cast_Long(
             g, squeeze(g, select(g, rois, 1, g.op("Constant", value_t=torch.tensor([0], dtype=torch.long))), 1), False
         )
-        rois = select(g, rois, 1, g.op("Constant", value_t=torch.tensor([1, 2, 3, 4], dtype=torch.long)))
-        # TODO: Remove this warning after ONNX opset 16 is supported.
-        if aligned:
-            warnings.warn(
-                "ROIAlign with aligned=True is not supported in ONNX, but will be supported in opset 16. "
-                "The workaround is that the user need apply the patch "
-                "https://github.com/microsoft/onnxruntime/pull/8564 "
-                "and build ONNXRuntime from source."
-            )
 
-        # ONNX doesn't support negative sampling_ratio
+    def _process_rois_for_roi_align(g, rois):
+        return select(g, rois, 1, g.op("Constant", value_t=torch.tensor([1, 2, 3, 4], dtype=torch.long)))
+
+    def _process_sampling_ratio_for_roi_align(g, sampling_ratio: int):
         if sampling_ratio < 0:
             warnings.warn(
-                "ONNX doesn't support negative sampling ratio, therefore is set to 0 in order to be exported."
+                "ONNX export for RoIAlign with a non-zero sampling_ratio is not supported. "
+                "The model will be exported with a sampling_ratio of 0."
             )
             sampling_ratio = 0
+        return sampling_ratio
+
+    @parse_args("v", "v", "f", "i", "i", "i", "i")
+    def roi_align_opset11(g, input, rois, spatial_scale, pooled_height, pooled_width, sampling_ratio, aligned):
+        batch_indices = _process_batch_indices_for_roi_align(g, rois)
+        rois = _process_rois_for_roi_align(g, rois)
+        if aligned:
+            warnings.warn(
+                "ROIAlign with aligned=True is not supported in ONNX, but is supported in opset 16. "
+                "Please export with opset 16 or higher to use aligned=False."
+            )
+        sampling_ratio = _process_sampling_ratio_for_roi_align(g, sampling_ratio)
+        return g.op(
+            "RoiAlign",
+            input,
+            rois,
+            batch_indices,
+            spatial_scale_f=spatial_scale,
+            output_height_i=pooled_height,
+            output_width_i=pooled_width,
+            sampling_ratio_i=sampling_ratio,
+        )
+
+    @parse_args("v", "v", "f", "i", "i", "i", "i")
+    def roi_align_opset16(g, input, rois, spatial_scale, pooled_height, pooled_width, sampling_ratio, aligned):
+        batch_indices = _process_batch_indices_for_roi_align(g, rois)
+        rois = _process_rois_for_roi_align(g, rois)
+        coordinate_transformation_mode = "half_pixel" if aligned else "output_half_pixel"
+        sampling_ratio = _process_sampling_ratio_for_roi_align(g, sampling_ratio)
         return g.op(
             "RoiAlign",
             input,
             rois,
             batch_indices,
+            coordinate_transformation_mode_s=coordinate_transformation_mode,
             spatial_scale_f=spatial_scale,
             output_height_i=pooled_height,
             output_width_i=pooled_width,
@@ -61,6 +87,7 @@ def _register_custom_op():
 
     from torch.onnx import register_custom_op_symbolic
 
-    register_custom_op_symbolic("torchvision::nms", symbolic_multi_label_nms, _onnx_opset_version)
-    register_custom_op_symbolic("torchvision::roi_align", roi_align, _onnx_opset_version)
-    register_custom_op_symbolic("torchvision::roi_pool", roi_pool, _onnx_opset_version)
+    register_custom_op_symbolic("torchvision::nms", symbolic_multi_label_nms, _onnx_opset_version_11)
+    register_custom_op_symbolic("torchvision::roi_align", roi_align_opset11, _onnx_opset_version_11)
+    register_custom_op_symbolic("torchvision::roi_align", roi_align_opset16, _onnx_opset_version_16)
+    register_custom_op_symbolic("torchvision::roi_pool", roi_pool, _onnx_opset_version_11)