[Bug]: Abnormal result of beam search operator

[magicheng0816]

Your environment

910C

🐛 Describe the bug

If the beam search operator is turned on and top-logrobots is set to be greater than the beam width, the value of srcseq_idxes in the beam search operator result will be abnormal, and a reasonable range of values should be smaller than sequences_. size()

[LMX-xin]

Setting top-logprobs greater than beam width is meaningless, because the top-logprobs obtained through the sampler are strictly ordered. When selecting beam-width tokens from beam-width * top-logprobs tokens, only the first beam-width tokens in each beam can possibly be selected; tokens beyond beam-width will definitely not be selected.

[XuZhang99]

so we need to add CHECK_GT(beam_width, top_logprobs).

[LMX-xin]

@yjw258 please fix it.