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LLMsID: classic-tasks

Classic NLP Tasks

经典 NLP 任务
🎯Core Definition
pre- vs post-LLM paradigms for four classic tasks. (1) Text classification — before: TF-IDF/BOW + LR/GBDT feature engineering, or BERT's [CLS] into softmax(Wh[CLS])\text{softmax}(W^\top h_{\text{[CLS]}}); after: zero/few-shot prompts assign labels, or distill into a small model for cost. (2) NER — before: sequence labeling BiLSTM-CRF over BIO tags; after: LLMs emit JSON entity lists, unconstrained label sets, new entity types with zero training. (3) MT — before: SMT (phrase statistics) to NMT (Seq2Seq + Attention, BLEU); after: one multilingual model plus glossary constraints in-context. (4) Summarization — before: extractive (TextRank) and abstractive (BART/Pegasus, ROUGE); after: Map-Reduce chunked summarization for very long documents.
💡Use Cases
tech-selection when migrating to LLMs; keep traditional small models where throughput, latency, or privacy dominate; a classic interview question — classifying 10M customer-support tickets, balancing LLM vs fine-tuned small models.
Key Problems Solved
the traditional paradigm needs task-specific labeled data, models, and feature engineering — slow cold starts per task. The LLM paradigm reduces task differences to prompt differences: few-shot cold start and reuse, at the cost of latency/cost/stability — which is why production often runs the hybrid "LLM annotates → distill to a small model" route.
🎯5 High-Frequency Exam Points
1
LLM vs BERT for classification: accuracy, cost, latency, and cold-start trade-offs?
2
Sequence-labeling NER (BIO, BiLSTM-CRF) vs LLM extraction: pros and cons of each?
3
Why was NMT replacing SMT a milestone, and what role did BLEU play?
4
How do you design Map-Reduce summarization for very long documents, and how do you mitigate information loss at merge?
5
LLM-to-small-model distillation pipeline: how do you build training data and measure distillation loss?
📖 In-depth Guide:📄 nlp-tasks-and-ner
Updated 2026-08-12
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