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BeaconCat f1b659e5ef membench: add LLM-as-Judge evaluation mode (#2484)
* membench: add LLM-as-Judge evaluation mode

Add --eval-mode=llm to membench for LLM-based answer generation and
semantic scoring via an OpenAI-compatible API endpoint.

New files:
- llm_client.go: generic OpenAI-compatible chat completion client
  with support for API key, configurable timeout, and optional
  chat_template_kwargs (for llama.cpp thinking models)
- eval_llm.go: LLM answer generation + LLM-as-Judge scoring for
  both legacy and seahorse retrieval modes

Changes to main.go:
- --eval-mode flag (token|llm) to select evaluation strategy
- --api-base, --api-key, --model flags with env var fallback
  (MEMBENCH_API_BASE, MEMBENCH_API_KEY, MEMBENCH_MODEL)
- --no-thinking flag for llama.cpp + Qwen thinking models
- --limit flag to cap QA questions per sample for quick testing

* style: fix golangci-lint formatting (gofmt + golines)

* fix: address Copilot review feedback

- Validate --model is required for LLM eval mode
- Use rune-based truncation to preserve valid UTF-8
- Precompute totalQA count outside inner loop
- Log SearchMessages errors instead of silently skipping

* fix: address Copilot review round 2

- Validate --eval-mode accepts only 'token' or 'llm'
- Normalize base URL to avoid /v1/v1 duplication
- Separate token/LLM results for correct PrintComparison labeling
- Log ExpandMessages errors instead of silently ignoring
- Short-circuit with 0 scores when no context retrieved (match token eval)
- Add --timeout flag wired to LLMClientOptions.Timeout

* fix: address review P1+P2 — sort alignment, failure sentinel, score parser

- P1: Replace hand-rolled sortByRank with sort.Slice (ascending, best
  first) matching eval.go's EvalSeahorse — ensures BudgetTruncate keeps
  best-ranked messages when truncation occurs
- P2: Use -1.0 sentinel for LLM API failures and parse errors, distinct
  from genuine 0.0 score; aggregateMetrics skips -1.0 entries for F1
  averaging while still counting HitRate
- P2: Use regexp \b([1-5])\b for judge score extraction instead of
  first-digit scan — avoids misparses on '5/5', 'Score: 3' etc.

* fix: address Copilot review round 2

- Fix F1/HitRate weighted aggregation: track ValidF1Count separately so
  computeModeAgg weights F1 by valid scores only, not TotalQuestions
- No-context retrieval failure uses 0.0 (genuine bad score) instead of
  -1.0 sentinel (reserved for API/parse failures)
- Validate --timeout > 0 to prevent disabling HTTP timeouts

* fix: remove hardcoded /v1 from API base URL

Users now provide the full versioned path in --api-base (e.g. /v1, /v4).
Code only appends /chat/completions. Default changed to
http://127.0.0.1:8080/v1 for backward compatibility.

* fix: address Copilot review round 3

- ValidF1Count=0 when all scores are sentinel (no forced =1)
- Backward compat: old eval JSON without ValidF1Count falls back to
  TotalQuestions in computeModeAgg
- Skip empty section in PrintComparison when tokenResults is empty
- Update --api-base flag help to document /v1 default and version path
- Add sentinel aggregation unit tests (partial, all, weighted)

* feat: add --retries flag with exponential backoff for transient LLM errors

Retry on timeout, 5xx, and 429 (rate limit) with 1s/2s/4s backoff.
Default 3 retries, configurable via --retries. Context cancellation
is respected between retries.

* fix: address Copilot review round 4

- runReport splits results by mode suffix into token/llm for PrintComparison
- backward compat fallback (ValidF1Count=0 -> TotalQuestions) only for
  non-LLM modes; LLM modes keep ValidF1Count=0 when all scores sentinel
- MaxRetries==0 means no retry; only negative falls back to default 3
- truncateStr uses []rune to avoid cutting multi-byte UTF-8 characters
- Complete() returns error on empty LLM response (vs silent empty string)

* feat: --no-thinking adapts to llama.cpp, Ollama, and GLM backends

Send all three disable-thinking fields simultaneously:
- chat_template_kwargs.enable_thinking=false (llama.cpp, GLM)
- think=false (Ollama 0.9+)
- thinking.type=disabled (GLM/Zhipu)
Each backend picks the field it recognizes and ignores the rest.
Also bumps max_tokens from 512 to 2048 for thinking models.

* feat: mixed model eval + concurrent QA workers

- Add --judge-model, --judge-api-base, --judge-api-key flags for separate judge model
- Add --concurrency flag (default 1) with semaphore-based goroutine pool
- Add reasoning_content fallback for GLM/DeepSeek style responses
- Prepend /no_think to system prompt for Ollama /v1 compatibility
- Reduce default MaxTokens from 2048 to 512 (answers are 1-3 sentences)
- Extract evalQAWorker and buildSeahorseContext for shared concurrent logic

---------

Co-authored-by: BeaconCat <BeaconCat@users.noreply.github.com>
2026-04-15 21:15:17 +08:00
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