[TVMC] Add test for quantized pytorch model

As a follow up to apache#9417 and now that apache#9362 is resolved, this PR adds a
test to check quantized pytorch mobilenetv2 is converted correctly.

Change-Id: Iaf2d38ce71c008e0141a4a2536bd54c2c9f3fe3d

tests/python/driver/tvmc/conftest.py

@@ -126,6 +126,23 @@ def pytorch_resnet18(tmpdir_factory):
     return model_file_name
 
 
+@pytest.fixture(scope="session")
+def pytorch_mobilenetv2_quantized(tmpdir_factory):
+    try:
+        import torch
+        import torchvision.models as models
+    except ImportError:
+        # Not all environments provide Pytorch, so skip if that's the case.
+        return ""
+    model = models.quantization.mobilenet_v2(quantize=True)
+    model_file_name = "{}/{}".format(tmpdir_factory.mktemp("data"), "mobilenet_v2_quantized.pth")
+    # Trace model into torchscript.
+    traced_cpu = torch.jit.trace(model, torch.randn(1, 3, 224, 224))
+    torch.jit.save(traced_cpu, model_file_name)
+
+    return model_file_name
+
+
 @pytest.fixture(scope="session")
 def onnx_resnet50():
     base_url = "https://github.com/onnx/models/raw/master/vision/classification/resnet/model"

tests/python/driver/tvmc/test_frontends.py

@@ -217,6 +217,21 @@ def test_load_model__pth(pytorch_resnet18):
     assert "layer1.0.conv1.weight" in tvmc_model.params.keys()
 
 
+def test_load_quantized_model__pth(pytorch_mobilenetv2_quantized):
+    # some CI environments wont offer torch, so skip in case it is not present
+    pytest.importorskip("torch")
+    pytest.importorskip("torchvision")
+
+    tvmc_model = tvmc.load(pytorch_mobilenetv2_quantized, shape_dict={"input": [1, 3, 224, 224]})
+    assert type(tvmc_model) is TVMCModel
+    assert type(tvmc_model.mod) is IRModule
+    assert type(tvmc_model.params) is dict
+
+    # checking weights remain quantized and are not float32
+    for p in tvmc_model.params.values():
+        assert p.dtype in ["int8", "uint8", "int32"]  # int32 for bias
+
+
 def test_load_model___wrong_language__to_pytorch(tflite_mobilenet_v1_1_quant):
     # some CI environments wont offer pytorch, so skip in case it is not present
     pytest.importorskip("torch")