[NPU] further fix of qwen2 int8 pipeline & C++ (#12449)

* fix

* fix style

Author: rnwang04

python/llm/src/ipex_llm/transformers/npu_model.py

@@ -231,7 +231,7 @@ def optimize_npu_model(cls, *args, **kwargs):
         from intel_npu_acceleration_library.compiler import create_npu_kernels
 
         model = kwargs.pop("model")
-        qtype = kwargs.pop("qtype", "sym_int4")
+        qtype = kwargs.pop("qtype", "sym_int4_rtn")
         mixed_precision = kwargs.pop("mixed_precision", False)
         quantization_group_size = kwargs.pop("quantization_group_size", 0)
         modules_to_not_convert = kwargs.pop("modules_to_not_convert", [])
@@ -280,6 +280,7 @@ def optimize_npu_model(cls, *args, **kwargs):
                         max_prompt_len=max_prompt_len,
                         transpose_value_cache=transpose_value_cache,
                         group_size=quantization_group_size,
+                        qtype=qtype,
                         convert_model=convert_model,
                         save_directory=save_directory)
         model.save_low_bit = types.MethodType(save_low_bit, model)

python/llm/src/ipex_llm/transformers/npu_pipeline_model/convert_pipeline.py

@@ -193,13 +193,18 @@ def convert_llm(model: torch.nn.Module,
                 max_prompt_len: int,
                 transpose_value_cache: bool,
                 group_size: int,
+                qtype: str,
                 convert_model: bool=False,
                 save_directory: str=None):
     # whether to set layernorm weight as const
     layernorm_const = os.environ.get("IPEX_LLM_LAYERNORM_CONST", "1") == "1"
     if group_size == 0:
         n_splits_linear = 1
-        n_splits_down_proj = 2 if model.config.intermediate_size == 18944 else 1
+        if qtype == "sym_int8_rtn":
+            # do not split mlp down_proj for Qwen2-7B & sym_int8
+            n_splits_down_proj = 1
+        else:
+            n_splits_down_proj = 2 if model.config.intermediate_size == 18944 else 1
     else:
         n_splits_linear = model.config.hidden_size // group_size
         n_splits_down_proj = model.config.intermediate_size // group_size