fix marianMT convertion to onnx (#19287)

* fix marianMT convertion to onnx

* Update src/transformers/onnx/convert.py
Co-authored-by: lewtun <lewis.c.tunstall@gmail.com>

* Update src/transformers/onnx/convert.py
Co-authored-by: lewtun <lewis.c.tunstall@gmail.com>
Co-authored-by: lewtun <lewis.c.tunstall@gmail.com>

src/transformers/models/marian/configuration_marian.py

@@ -392,3 +392,7 @@ class MarianOnnxConfig(OnnxSeq2SeqConfigWithPast):
             flattened_output = super(OnnxSeq2SeqConfigWithPast, self)._flatten_past_key_values_(
                 flattened_output, name, idx, t
             )
+
+    @property
+    def atol_for_validation(self) -> float:
+        return 1e-4

src/transformers/onnx/convert.py

@@ -450,10 +450,12 @@ def validate_model_outputs(
 
         # Values
         if not np.allclose(ref_value, ort_value, atol=atol):
+            bad_indices = np.logical_not(np.isclose(ref_value, ort_value, atol=atol))
             logger.info(f"\t\t-[x] values not close enough (atol: {atol})")
             raise ValueError(
                 "Outputs values doesn't match between reference model and ONNX exported model: "
-                f"Got max absolute difference of: {np.amax(np.abs(ref_value - ort_value))}"
+                f"Got max absolute difference of: {np.amax(np.abs(ref_value - ort_value))} for "
+                f"{ref_value[bad_indices]} vs {ort_value[bad_indices]}"
             )
         else:
             logger.info(f"\t\t-[✓] all values close (atol: {atol})")