GPU does not work on llamacpp(langchain) , please help.

Hi, I have an issue related to GPU acceleration.
When I execute the following command, the GPU does not work on 2.
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Command1 :
./main -m /MYPATH/ggml-model-q4_0.bin --color -p "MYQUESTION" -n 256 -ngl 45 --in-prefix

Result1 : blas=1 (80 tokens/s)
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However, when I use the LlamaCpp model with GPU acceleration, it shows a lower speed.

Command2 :
callback_manager = CallbackManager([StreamingStdOutCallbackHandler()])
llm = LlamaCpp(
model_path="/MYPATH/ggml-model-q4_0.bin",
n_gpu_layers=45,
n_batch=512,
max_length=1024,
n_ctx=1024,
callback_manager=callback_manager,
verbose=True
)
llm.predict("MYQUESTION")

Result2 : blas=0 (7.8 tokens/s)
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I'm wondering if there might be any possible reasons for this discrepancy. Can you help me identify and correct the issue?