slime

# slime: LLM Post-Training Framework for RL Scaling slime is an LLM post-training framework from Tsinghua's THUDM team, powering GLM-4.5, GLM-4.6, and GLM-4.7. It connects Megatron-LM for training with SGLang for high-throughput rollout generation. ## When to Use slime **Choose slime when you need:** - Megatron-LM native training with SGLang inference - Custom data generation workflows with flexible data buffers - Training GLM, Qwen3, DeepSeek V3, or Llama 3 models - Research-grade framework with production backing (Z.ai) **Consider alternatives when:** - You need enterprise-grade stability features → use **miles** - You want flexible backend swapping → use **verl** - You need PyTorch-native abstractions → use **torchforge** ## Key Features - **Training**: Megatron-LM with full parallelism support (TP, PP, DP, SP) - **Rollout**: SGLang-based high-throughput generation with router - **Data Buffer**: Flexible prompt management and sample storage - **Models**: GLM-4.x, Qwen3, DeepSeek V3/R1, Llama 3 ## Architecture Overview ``` ┌─────────────────────────────────────────────────────────┐ │ Data Buffer │ │ - Prompt initialization and management │ │ - Custom data generation and filtering │ │ - Rollout sample storage │ └─────────────┬───────────────────────────┬───────────────┘ │ │ ┌─────────────▼───────────┐ ┌─────────────▼───────────────┐ │ Training (Megatron-LM) │ │ Rollout (SGLang + Router) │ │ - Actor model training │ │ - Response generation │ │ - Critic (optional) │ │ - Reward/verifier output │ │ - Weight sync to rollout│ │ - Multi-turn support │ └─────────────────────────┘ └─────────────────────────────┘ ``` ## Installation ```bash # Recommended: Docker docker pull slimerl/slime:latest docker run --rm --gpus all --ipc=host --shm-size=16g \ -it slimerl/slime:latest /bin/bash # Inside container cd /root/slime && pip install -e . --no-deps ``` ### From Source ```bash git clone https://github.com/THUDM/slime.git cd slime pip install -r requirements.txt pip install -e . ``` ## Quick Start: GRPO Training ```bash # Source model configuration source scripts/models/qwen3-4B.sh # Launch training python train.py \ --actor-num-nodes 1 \ --actor-num-gpus-per-node 4 \ --rollout-num-gpus 4 \ --advantage-estimator grpo \ --use-kl-loss --kl-loss-coef 0.001 \ --rollout-batch-size 32 \ --n-samples-per-prompt 8 \ --global-batch-size 256 \ --num-rollout 3000 \ --prompt-data /path/to/data.jsonl \ ${MODEL_ARGS[@]} ${CKPT_ARGS[@]} ``` --- ## Workflow 1: Standard GRPO Training Use this workflow for training reasoning models with group-relative advantages. ### Prerequisites Checklist - [ ] Docker environment or Megatron-LM + SGLang installed - [ ] Model checkpoint (HuggingFace or Megatron format) - [ ] Training data in JSONL format ### Step 1: Prepare Data ```python # data.jsonl format {"prompt": "What is 2 + 2?", "label": "4"} {"prompt": "Solve: 3x = 12", "label": "x = 4"} ``` Or with chat format: ```python { "prompt": [ {"role": "system", "content": "You are a math tutor."}, {"role": "user", "content": "What is 15 + 27?"} ], "label": "42" } ``` ### Step 2: Configure Model Choose a pre-configured model script: ```bash # List available models ls scripts/models/ # glm4-9B.sh, qwen3-4B.sh, qwen3-30B-A3B.sh, deepseek-v3.sh, llama3-8B.sh, ... # Source your model source scripts/models/qwen3-4B.sh ``` ### Step 3: Launch Training ```bash python train.py \ --actor-num-nodes 1 \ --actor-num-gpus-per-node 8 \ --rollout-num-gpus 8 \ --advantage-estimator grpo \ --use-kl-loss \ --kl-loss-coef 0.001 \ --prompt-data /path/to/train.jsonl \ --input-key prompt \ --label-key label \ --apply-chat-template \ --rollout-batch-size 32 \ --n-samples-per-prompt 8 \ --global-batch-size 256 \ --num-rollout 3000 \ --save-interval 100 \ --eval-interval 50 \ ${MODEL_ARGS[@]} ``` ### Step 4: Monitor Training - [ ] Check TensorBoard: `tensorboard --logdir outputs/` - [ ] Verify reward curves are increasing - [ ] Monitor GPU utilization across nodes --- ## Workflow 2: Asynchronous Training Use async mode for higher throughput by overlapping rollout and training. ### When to Use Async - Large models with long generation times - High GPU idle time in synchronous mode - Sufficient memory for buffering ### Launch Async Training ```bash python train_async.py \ --actor-num-nodes 1 \ --actor-num-gpus-per-node 8 \ --rollout-num-gpus 8 \ --advantage-estimator grpo \ --async-buffer-size 4 \ --prompt-data /path/to/train.jsonl \ ${MODEL_ARGS[@]} ``` ### Async-Specific Parameters ```bash --async-buffer-size 4 # Number of rollouts to buffer --update-weights-interval 2 # Sync weights every N rollouts ``` --- ## Workflow 3: Multi-Turn Agentic Training Use this workflow for training agents with tool use or multi-step reasoning. ### Prerequisites - [ ] Custom generate function for multi-turn logic - [ ] Tool/environment interface ### Step 1: Define Custom Generate Function ```python # custom_generate.py async def custom_generate(args, samples, evaluation=False): """Multi-turn generation with tool calling.""" for sample in samples: conversation = sample.prompt for turn in range(args.max_turns): # Generate response response = await generate_single(conversation) # Check for tool call tool_call = extract_tool_call(response) if tool_call: tool_result = execute_tool(tool_call) conversation.append({"role": "assistant", "content": response}) conversation.append({"role": "tool", "content": tool_result}) else: break sample.response = response sample.reward = compute_reward(sample) return samples ``` ### Step 2: Launch with Custom Function ```bash python train.py \ --custom-generate-function-path custom_generate.py \ --max-turns 5 \ --prompt-data /path/to/agent_data.jsonl \ ${MODEL_ARGS[@]} ``` See `examples/search-r1/` for a complete multi-turn search example. --- ## Configuration Reference ### Three Argument Categories slime uses three types of arguments: **1. Megatron Arguments** (passed directly): ```bash --tensor-model-parallel-size 2 --pipeline-model-parallel-size 1 --num-layers 32 --hidden-size 4096 ``` **2. SGLang Arguments** (prefixed with `--sglang-`): ```bash --sglang-mem-fraction-static 0.8 --sglang-context-length 8192 --sglang-log-level INFO ``` **3. slime Arguments**: ```bash # Resource allocation --actor-num-nodes 1 --actor-num-gpus-per-node 8 --rollout-num-gpus 8 --colocate # Share GPUs between training/inference # Data --prompt-data /path/to/data.jsonl --input-key prompt --label-key label # Training loop --num-rollout 3000 --rollout-batch-size 32 --n-samples-per-prompt 8 --global-batch-size 256 # Algorithm --advantage-estimator grpo # or: gspo, ppo, reinforce_plus_plus --use-kl-loss --kl-loss-coef 0.001 ``` ### Key Constraints ``` rollout_batch_size × n_samples_per_prompt = global_batch_size × num_steps_per_rollout ``` Example: 32 × 8 = 256 × 1 --- ## Data Buffer System slime's data buffer enables flexible data management: ### Basic Data Source ```python class RolloutDataSource: def get_samples(self, num_samples): """Fetch prompts from dataset.""" return self.dataset.sample(num_samples) def add_samples(self, samples): """Called after generation (no-op by default).""" pass ``` ### Buffered Data Source (Off-Policy) ```python class RolloutDataSourceWithBuffer(RolloutDataSource): def __init__(self): self.buffer = [] def add_samples(self, samples): """Store generated samples for reuse.""" self.buffer.extend(samples) def buffer_filter(self, args, buffer, num_samples): """Custom selection logic (prioritized, stratified, etc.).""" return select_best(buffer, num_samples) ``` --- ## Common Issues and Solutions ### Issue: SGLang Engine Crash **Symptoms**: Inference engine dies mid-training **Solutions**: ```bash # Enable fault tolerance --use-fault-tolerance # Increase memory allocation --sglang-mem-fraction-static 0.85 # Reduce batch size --rollout-batch-size 16 ``` ### Issue: Weight Sync Timeout **Symptoms**: Training hangs after rollout **Solutions**: ```bash # Increase sync interval --update-weights-interval 5 # Use colocated mode (no network transfer) --colocate ``` ### Issue: OOM During Training **Symptoms**: CUDA OOM in backward pass **Solutions**: ```bash # Enable gradient checkpointing --recompute-activations # Reduce micro-batch size --micro-batch-size 1 # Enable sequence parallelism --sequence-parallel ``` ### Issue: Slow Data Loading **Symptoms**: GPU idle during data fetch **Solutions**: ```bash # Increase data workers --num-data-workers 4 # Use streaming dataset --streaming-data ``` --- ## Supported Models | Model Family | Configurations | |--------------|----------------| | GLM | GLM-4.5, GLM-4.6, GLM-4.7, GLM-Z1-9B | | Qwen | Qwen3 (4B, 8B, 30B-A3B), Qwen3-MoE, Qwen2.5 | | DeepSeek | V3, V3.1, R1 | | Llama | Llama 3 (8B, 70B) | | Others | Kimi K2, Moonlight-16B | Each model has pre-configured scripts in `scripts/models/`. --- ## Advanced Topics ### Co-location Mode Share GPUs between training and inference to reduce memory: ```bash python train.py \ --colocate \ --actor-num-gpus-per-node 8 \ --sglang-mem-fraction-static 0.4 \ ${MODEL_ARGS[@]} ``` ### Custom Reward Model ```python # custom_rm.py class CustomRewardModel: def __init__(self, model_path): self.model = load_model(model_path) def compute_reward(self, prompts, responses): inputs = self.tokenize(prompts, responses) scores = self.model(inputs) return scores.tolist() ``` ```bash --custom-rm-path custom_rm.py ``` ### Evaluation Multi-Task ```bash --eval-prompt-data aime /path/to/aime.jsonl \ --eval-prompt-data gsm8k /path/to/gsm8k.jsonl \ --n-samples-per-eval-prompt 16 ``` --- ## Resources - **Documentation**: https://thudm.github.io/slime/ - **GitHub**: https://github.com/THUDM/slime - **Blog**: https://lmsys.org/blog/2025-07-09-slime/ - **Examples**: See `examples/` directory for 14+ worked examples