Workaround: Remove non-utf at start of triton response string (#501)

* Workaround: Remove non-utf at start of triton response string

* Fix formatting failures

---------

Co-authored-by: Elias Bermudez <[email protected]>

src/c++/perf_analyzer/genai-pa/genai_pa/llm_metrics.py

@@ -372,9 +372,24 @@ def _parse_requests(self, requests: dict) -> LLMMetrics:
             num_generated_tokens,
         )
 
+    def _remove_leading_invalid_chars(self, text: str):
+        for i, char in enumerate(text):
+            # There will be 3 or 4 chars
+            # (but sometimes the first char looks valid, so don't stop until we've seen at least 3)
+            if char.isprintable() and i > 2:
+                break
+
+        return text[i:]
+
     def _preprocess_response(
         self, res_timestamps: list[int], res_outputs: list[dict[str, str]]
     ) -> None:
+        # FIXME -- remove this triton code once it is properly fixed in PA
+        # (PA/triton will add junk to the start of the BYTES array. Remove it here)
+        if self._service_kind == "triton":
+            for d in res_outputs:
+                d["text_output"] = self._remove_leading_invalid_chars(d["text_output"])
+
         """Helper function to preprocess responses of a request."""
         if self._service_kind == "openai":
             openai_final_response = res_outputs[-1]["response"]

src/c++/perf_analyzer/genai-pa/genai_pa/utils.py

@@ -33,7 +33,7 @@ def remove_sse_prefix(msg: str) -> str:
 
 
 def load_json(filename: str):
-    with open(filename) as f:
+    with open(filename, encoding="utf-8", errors="ignore") as f:
         return json.load(f)