quant: nice error message on convtranspose with per-channel weight

test/quantization/test_quantize.py

@@ -726,6 +726,20 @@ def forward(self, x):
         ref_res = ref_m(data)
         self.assertEqual(res, ref_res)
 
+    @skipIfNoFBGEMM
+    def test_convtranspose_per_channel_fails_early(self):
+        r"""
+        Verifies that attempting to quantize a ConvTranspose module with per-Channel
+        weight observers fails in the prepare step, as opposed to the convert step.
+        """
+        m = torch.nn.Sequential(torch.nn.ConvTranspose2d(1, 1, 1))
+        m.qconfig = torch.quantization.get_default_qconfig('fbgemm')
+        with self.assertRaises(AssertionError) as context:
+            mp = torch.quantization.prepare(m)
+        self.assertTrue(
+            str(context.exception) ==
+            'Per channel weight observer is not supported yet for ConvTranspose{n}d.')
+
 
 @skipIfNoFBGEMM
 class TestPostTrainingDynamic(QuantizationTestCase):

test/quantization/test_quantize_fx.py

@@ -1275,6 +1275,21 @@ def test_fp32_input_fp32_output(self):
         self._test_quantized_inputs_outputs(
             prepare_custom_config_dict, prepare_count_check, convert_count_check)
 
+    @skipIfNoFBGEMM
+    def test_convtranspose_per_channel_fails_early(self):
+        r"""
+        Verifies that attempting to quantize a ConvTranspose module with per-Channel
+        weight observers fails in the prepare step, as opposed to the convert step.
+        """
+        m = torch.nn.Sequential(torch.nn.ConvTranspose2d(1, 1, 1))
+        m.eval()
+        qconfig_dict = {'': torch.quantization.get_default_qconfig('fbgemm')}
+        with self.assertRaises(AssertionError) as context:
+            mp = prepare_fx(m, qconfig_dict)
+        self.assertTrue(
+            str(context.exception) ==
+            'Per channel weight observer is not supported yet for ConvTranspose{n}d.')
+
 @skipIfNoFBGEMM
 class TestQuantizeFxOps(QuantizationTestCase):
     """Unit tests for individual ops

torch/quantization/qconfig.py

@@ -3,6 +3,8 @@
 from .fake_quantize import *
 import torch.nn as nn
 
+from typing import Union
+
 class QConfig(namedtuple('QConfig', ['activation', 'weight'])):
     """
     Describes how to quantize a layer or a part of the network by providing
@@ -109,3 +111,18 @@ def get_default_qat_qconfig(backend='fbgemm'):
     else:
         qconfig = default_qat_qconfig
     return qconfig
+
+def assert_valid_qconfig(qconfig: Union[QConfig, QConfigDynamic],
+                         mod: torch.nn.Module) -> None:
+    is_conv_transpose_mod = (
+        isinstance(mod, torch.nn.ConvTranspose1d) or
+        isinstance(mod, torch.nn.ConvTranspose2d) or
+        isinstance(mod, torch.nn.ConvTranspose3d))
+    if is_conv_transpose_mod:
+        example_observer = qconfig.weight()
+        is_per_channel = (
+            isinstance(example_observer, torch.quantization.PerChannelMinMaxObserver),
+            isinstance(example_observer, torch.quantization.MovingAveragePerChannelMinMaxObserver),
+        )
+        assert not is_per_channel, \
+            'Per channel weight observer is not supported yet for ConvTranspose{n}d.'

torch/quantization/quantize.py

@@ -49,6 +49,8 @@ def _propagate_qconfig_helper(module, qconfig_dict, allow_list=None,
     module_qconfig = qconfig_dict.get(prefix, module_qconfig)
     module_qconfig = getattr(module, 'qconfig', module_qconfig)
 
+    torch.quantization.qconfig.assert_valid_qconfig(module_qconfig, module)
+
     module.qconfig = module_qconfig
     for name, child in module.named_children():
         module_prefix = prefix + '.' + name if prefix else name