distributed RPC-based speculative evaluation

[okuvshynov]

plan copypasta from ggerganov/llama.cpp#6853 (reply in thread):

We might not even need to write too much new code for this, I suppose. Given that models are separate, we can start (main_A + speculative) on instance_A, (main_B + speculative) on instance_B. Then we need to orchestrate the data/logic passing during transition phase:

In the 'middle' of main model processing (A is done with first half), we need to pass activations to B and whatever B speculated so far back to A
At the end of main model processing (B is done with logits) we need to get whatever latest speculation on B is, consolidate it with what we have currently produced on A, pass the 'current approved tokens' to A, start speculating on B.
repeat

Relevant links:

• async/parallel speculative execution ggerganov/llama.cpp#6853
• speculative : add tree-based sampling example ggerganov/llama.cpp#3624
• ggml : add RPC backend ggerganov/llama.cpp#6829

Devices I can test it on are:

• M2 Ultra 192GB
• M2 24GB
• M1 16GB

[okuvshynov]

Work will be done here: https://github.com/okuvshynov/llama.cpp/tree/duo, as I'll need some changes to llama.cpp itself.