Retrieval: Fix Memory Leak in Retrieval Query Handling

[gtygo]

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• Description This pull request addresses a memory leak issue in the retrieval.cpp file, specifically when continuously accepting query inputs. The problem arises from the llama_batch initialization and clearing process.

• Problem The llama_batch_init function allocates memory on the heap for the batch. However, the current implementation uses llama_batch_clear to reset the batch size to 0, which does not properly free the allocated heap memory. This results in a continuous increase in memory usage as the process runs.

• Solution The solution involves ensuring that the allocated memory for llama_batch is properly freed after each query is processed. This prevents the memory leak and stabilizes the memory usage of the process.

• Changes Replaced llama_batch_clear with llama_batch_free to ensure proper memory deallocation.