Enable / Add llama.cpp.python server --parallel | -np N | --n_parallel N

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When executing chat completions I need to wait for a prompt to complete before executing a new one. I'd like to be able to execute multiple prompts at the same time. Right now my GPU utilization on a g4dn.2xlarge instance is max 65-80% (model loaded in GPU mem) I've tinkered around with n_batch, ctx and a few other parameters.

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It seems like llama.cpp has this feature already -np N, --parallel N: Set the number of slots for process requests. Default: 1
https://github.com/ggerganov/llama.cpp/tree/master/examples/server

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