Raise an error when OVQuantizer is invoked on an compressed model

optimum/intel/openvino/quantization.py

@@ -1010,6 +1010,7 @@ def _weight_only_quantization(
     calibration_dataset: Optional[Union[nncf.Dataset, Iterable]] = None,
     **kwargs,
 ) -> openvino.runtime.Model:
+    _verify_not_optimized(model)
     config = quantization_config
     if isinstance(config, dict):
         config = OVWeightQuantizationConfig.from_dict(quantization_config)
@@ -1066,6 +1067,7 @@ def _full_quantization(
     calibration_dataset: nncf.Dataset,
     **kwargs,
 ):
+    _verify_not_optimized(model)
     advanced_parameters_kwargs = {}
     if quantization_config.smooth_quant_alpha is not None:
         advanced_parameters_kwargs["smooth_quant_alphas"] = AdvancedSmoothQuantParameters(
@@ -1187,3 +1189,20 @@ def _hybrid_quantization(
         **kwargs,
     )
     return quantized_model
+
+
+def _verify_not_optimized(ov_model):
+    message_template = (
+        "Cannot apply optimization to the model because it was already optimized with the following config: {}. "
+        "To avoid this issue, check that you set load_in_8bit=False or not using quantization_config at export in the .from_pretrained(), "
+        "or explicitly specify weight format with --weight_format fp16/fp32 when using CLI."
+    )
+
+    rt_info = ov_model.get_rt_info()
+    if "nncf" in rt_info:
+        model_weight_compression_config = rt_info["nncf"].get("weight_compression", None)
+        model_quantization_config = rt_info["nncf"].get("quantization", None)
+        if model_weight_compression_config is not None:
+            raise RuntimeError(message_template.format(model_weight_compression_config))
+        elif model_quantization_config is not None:
+            raise RuntimeError(message_template.format(model_quantization_config))

tests/openvino/test_quantization.py

@@ -214,6 +214,9 @@ def preprocess_function(examples, tokenizer):
             # Verify that the configuration is correctly saved and loaded
             loaded_config = OVConfig.from_pretrained(tmp_dir)
             self.assertEqual(ov_config.quantization_config.to_dict(), loaded_config.quantization_config.to_dict())
+            check_optimization_not_applicable_to_optimized_model(
+                model, quantization_config=OVWeightQuantizationConfig(bits=8)
+            )
 
     @parameterized.expand(SUPPORTED_ARCHITECTURES_OV_MODEL_WITH_AUTO_DATASET)
     def test_ov_model_static_quantization_with_auto_dataset(
@@ -718,6 +721,13 @@ def test_ovmodel_load_with_compressed_weights(self, model_cls, model_type, trust
         else:
             models = [model]
 
+        if model_type == "open-clip":
+            pytest.skip(reason="ticket 161043")
+        elif model_type == "t5":
+            pytest.skip(reason="ticket 160958")
+        else:
+            check_optimization_not_applicable_to_optimized_model(model, quantization_config={"bits": 8})
+
         expected_ov_int8 = _ARCHITECTURES_TO_EXPECTED_INT8[model_type]
         for i, model in enumerate(models):
             _, num_weight_nodes = get_num_quantized_nodes(model)
@@ -738,6 +748,7 @@ def test_ovmodel_hybrid_quantization(self, model_cls, model_type, expected_fake_
             self.assertEqual(0, num_weight_nodes["int4"])
 
             model.save_pretrained(tmp_dir)
+            check_optimization_not_applicable_to_optimized_model(model, quantization_config)
 
     def test_stable_diffusion_with_weight_compression(self):
         int8_pipe = OVStableDiffusionPipeline.from_pretrained(model_id=MODEL_NAMES["stable-diffusion"], export=True)
@@ -752,6 +763,10 @@ def test_stable_diffusion_with_weight_compression(self):
         self.assertEqual(0, num_fake_nodes)
         self.assertEqual(242, num_weight_nodes["int8"])
         self.assertEqual(0, num_weight_nodes["int4"])
+        quantization_config = OVWeightQuantizationConfig(
+            bits=8, dataset="conceptual_captions", num_samples=2, quant_method=OVQuantizationMethod.HYBRID
+        )
+        check_optimization_not_applicable_to_optimized_model(int8_pipe, quantization_config)
 
     @parameterized.expand(SUPPORTED_ARCHITECTURES_WITH_HYBRID_QUANTIZATION[-1:])
     def test_ovmodel_hybrid_quantization_with_custom_dataset(
@@ -797,6 +812,7 @@ def test_ovmodel_4bit_auto_compression(self, model_cls, model_type, expected_ov_
             if model_id == "facebook/opt-125m":
                 for key, value in self.DEFAULT_INT4_CONFIG.items():
                     self.assertEqual(value, getattr(openvino_config.quantization_config, key))
+            check_optimization_not_applicable_to_optimized_model(model, quantization_config={"bits": 8})
 
     @parameterized.expand(LOAD_IN_4_BITS_SCOPE)
     def test_ovmodel_4bit_auto_compression_with_config(
@@ -1321,3 +1337,12 @@ def test_calibration_data_uniqueness(self, model_name, apply_caching):
         else:
             # Without caching, encoder hidden states tensors will be unique for each collected input
             self.assertGreater(len(data_id_per_key["encoder_hidden_states"]), 2)
+
+
+def check_optimization_not_applicable_to_optimized_model(model, quantization_config):
+    quantizer = OVQuantizer(model)
+    with pytest.raises(
+        RuntimeError,
+        match="Cannot apply optimization to the model because it was already optimized with the following config",
+    ):
+        quantizer.quantize(ov_config=OVConfig(quantization_config=quantization_config))