Length Penalty only affects beam search

[jacob-mink-1996]

In the docs, it specifies that length_penalty is only for beam search - that means that in multinomial sampling, length_penalty does not change the generation.

openvino.genai/src/cpp/include/openvino/genai/generation_config.hpp

Line 51 in 7954d82

* @param length_penalty exponential penalty to the length that is used with beam-based generation. It is applied as an exponent to

It would be useful if length_penalty could be used in combination with max_length or max_new_tokens in order to scale the importance of the eos token during multinomial sampling, then it would help to get prompt results that end more naturally as the max_length limit approaches.

[Wovchena]

@sbalandi, is length_penalty applied to greedy and multinational after the implementation switched to the Sampler? If so, please update doc strings for C++ and Python.

[sbalandi]

no, length_penalty is supported for beam search only now