[Bugfix] Fix deepseekv3 grouped topk error

[Chen-XiaoBing]

Fix the logic in grouped topk computation of fused moe.

There is a slight difference between vllm grouped_topk and the official code. When the newly-introduced bias term (e_score_correction_bias in vllm) is not None, we should firstly get the top-2 scores of each group, and use the summation to get top-k groups. You can also check the compute logic in DeepSeek v3's official inference code

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[mgoin]

Thank you for your contribution!

I ran a quick eval on gsm8k with DeepSeek R1 and see that this PR seems to slightly regress performance, however it is within stderr.

(vllm) ➜  vllm git:(main) lm_eval --model vllm --model_args pretrained=/home/vllm-dev/DeepSeek-R1,tensor_parallel_size=8 --trust_remote_code --tasks gsm8k --num_fewshot 5 --batch_size auto
vllm (pretrained=/home/vllm-dev/DeepSeek-R1,tensor_parallel_size=8,trust_remote_code=True), gen_kwargs: (None), limit: None, num_fewshot: 5, batch_size: auto
|Tasks|Version|     Filter     |n-shot|  Metric   |   |Value|   |Stderr|
|-----|------:|----------------|-----:|-----------|---|----:|---|-----:|
|gsm8k|      3|flexible-extract|     5|exact_match|↑  |0.956|±  |0.0056|
|     |       |strict-match    |     5|exact_match|↑  |0.956|±  |0.0056|

(vllm) ➜  vllm git:(fix-dsv3-grouped-topk) lm_eval --model vllm --model_args pretrained=/home/vllm-dev/DeepSeek-R1,tensor_parallel_size=8 --trust_remote_code --tasks gsm8k --num_fewshot 5 --batch_size auto
vllm (pretrained=/home/vllm-dev/DeepSeek-R1,tensor_parallel_size=8,trust_remote_code=True), gen_kwargs: (None), limit: None, num_fewshot: 5, batch_size: auto
|Tasks|Version|     Filter     |n-shot|  Metric   |   |Value |   |Stderr|
|-----|------:|----------------|-----:|-----------|---|-----:|---|-----:|
|gsm8k|      3|flexible-extract|     5|exact_match|↑  |0.9507|±  | 0.006|
|     |       |strict-match    |     5|exact_match|↑  |0.9507|±  | 0.006|

I will try to run harder evals to determine improvement. Would you have an example of bad performance from DeepSeek on main due to this issue?

[simon-mo]

@mgoin, we might need to test V3 model as it is more trained for GSM and MMLU.

[mgoin]

Here is MMLU for R1, similar small drops for each category - I'll try to get V3 going on another machine

(vllm) ➜  vllm git:(main) lm_eval --model vllm --model_args pretrained=/home/vllm-dev/DeepSeek-R1,tensor_parallel_size=8,max_model_len=2048,gpu_memory_utilization=0.8 --trust_remote_code --tasks mmlu --batch_size 16
vllm (pretrained=/home/vllm-dev/DeepSeek-R1,tensor_parallel_size=8,max_model_len=2048,gpu_memory_utilization=0.8,trust_remote_code=True), gen_kwargs: (None), limit: None, num_fewshot: None, batch_size: 16

|      Groups      |Version|Filter|n-shot|Metric|   |Value |   |Stderr|
|------------------|------:|------|------|------|---|-----:|---|-----:|
|mmlu              |      2|none  |      |acc   |↑  |0.8514|±  |0.0029|
| - humanities     |      2|none  |      |acc   |↑  |0.7845|±  |0.0057|
| - other          |      2|none  |      |acc   |↑  |0.8822|±  |0.0055|
| - social sciences|      2|none  |      |acc   |↑  |0.9227|±  |0.0047|
| - stem           |      2|none  |      |acc   |↑  |0.8513|±  |0.0062|

(vllm) ➜  vllm git:(fix-dsv3-grouped-topk) lm_eval --model vllm --model_args pretrained=/home/vllm-dev/DeepSeek-R1,tensor_parallel_size=8,max_model_len=2048,gpu_memory_utilization=0.8 --trust_remote_code --tasks mmlu --batch_size 16
vllm (pretrained=/home/vllm-dev/DeepSeek-R1,tensor_parallel_size=8,max_model_len=2048,gpu_memory_utilization=0.8,trust_remote_code=True), gen_kwargs: (None), limit: None, num_fewshot: None, batch_size: 16
|      Groups      |Version|Filter|n-shot|Metric|   |Value |   |Stderr|
|------------------|------:|------|------|------|---|-----:|---|-----:|
|mmlu              |      2|none  |      |acc   |↑  |0.8492|±  |0.0029|
| - humanities     |      2|none  |      |acc   |↑  |0.7824|±  |0.0057|
| - other          |      2|none  |      |acc   |↑  |0.8806|±  |0.0055|
| - social sciences|      2|none  |      |acc   |↑  |0.9194|±  |0.0048|
| - stem           |      2|none  |      |acc   |↑  |0.8493|±  |0.0062|

[simon-mo]

I'll release v0.7.3 after this PR is merged.

[Chen-XiaoBing]

@simon-mo Some checks in the CI pipeline have failed. Would you kindly assist with merging the code?