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Reference-free preference alignment, simpler than DPO.

Skill metadata


Source	Optional — install with `mibyan skills install official/mlops/simpo`
Path	`optional-skills/mlops/simpo`
Version	`1.0.0`
Author	Orchestra Research
License	MIT
Dependencies	`torch`, `transformers`, `datasets`, `trl`, `accelerate`
Platforms	linux, macos, windows
Tags	`Post-Training`, `SimPO`, `Preference Optimization`, `Alignment`, `DPO Alternative`, `Reference-Free`, `LLM Alignment`, `Efficient Training`

Reference: full SKILL.md

The following is the complete skill definition that Mibyan loads when this skill is triggered. This is what the agent sees as instructions when the skill is active.

SimPO - Simple Preference Optimization

Quick start

SimPO is a reference-free preference optimization method that outperforms DPO without needing a reference model. Installation:

# Create environment
conda create -n simpo python=3.10 && conda activate simpo

# Install PyTorch 2.2.2
# Visit: https://pytorch.org/get-started/locally/

# Install alignment-handbook
git clone https://github.com/huggingface/alignment-handbook.git
cd alignment-handbook
python -m pip install .

# Install Flash Attention 2
python -m pip install flash-attn --no-build-isolation

Training (Mistral 7B):

ACCELERATE_LOG_LEVEL=info accelerate launch \
  --config_file accelerate_configs/deepspeed_zero3.yaml \
  scripts/run_simpo.py \
  training_configs/mistral-7b-base-simpo.yaml

Common workflows

Workflow 1: Train from base model (Mistral 7B)

Config (mistral-7b-base-simpo.yaml):

# Model
model_name_or_path: mistralai/Mistral-7B-v0.1
torch_dtype: bfloat16

# Dataset
dataset_mixer:
  HuggingFaceH4/ultrafeedback_binarized: 1.0
dataset_splits:
  - train_prefs
  - test_prefs

# SimPO hyperparameters
beta: 2.0                  # Reward scaling (2.0-10.0)
gamma_beta_ratio: 0.5       # Target margin (0-1)
loss_type: sigmoid          # sigmoid or hinge
sft_weight: 0.0             # Optional SFT regularization

# Training
learning_rate: 5e-7         # Critical: 3e-7 to 1e-6
num_train_epochs: 1
per_device_train_batch_size: 1
gradient_accumulation_steps: 8

# Output
output_dir: ./outputs/mistral-7b-simpo

Launch training:

accelerate launch --config_file accelerate_configs/deepspeed_zero3.yaml \
  scripts/run_simpo.py training_configs/mistral-7b-base-simpo.yaml

Workflow 2: Fine-tune instruct model (Llama 3 8B)

Config (llama3-8b-instruct-simpo.yaml):

model_name_or_path: meta-llama/Meta-Llama-3-8B-Instruct

dataset_mixer:
  argilla/ultrafeedback-binarized-preferences-cleaned: 1.0

beta: 2.5
gamma_beta_ratio: 0.5
learning_rate: 5e-7
sft_weight: 0.1             # Add SFT loss to preserve capabilities

num_train_epochs: 1
per_device_train_batch_size: 2
gradient_accumulation_steps: 4
output_dir: ./outputs/llama3-8b-simpo

Launch:

accelerate launch --config_file accelerate_configs/deepspeed_zero3.yaml \
  scripts/run_simpo.py training_configs/llama3-8b-instruct-simpo.yaml

Workflow 3: Reasoning-intensive tasks (lower LR)

For math/code tasks:

model_name_or_path: deepseek-ai/deepseek-math-7b-base

dataset_mixer:
  argilla/distilabel-math-preference-dpo: 1.0

beta: 5.0                   # Higher for stronger signal
gamma_beta_ratio: 0.7       # Larger margin
learning_rate: 3e-7         # Lower LR for reasoning
sft_weight: 0.0

num_train_epochs: 1
per_device_train_batch_size: 1
gradient_accumulation_steps: 16

When to use vs alternatives

Use SimPO when:

Want simpler training than DPO (no reference model)
Have preference data (chosen/rejected pairs)
Need better performance than DPO
Limited compute resources
Single-node training sufficient

Algorithm selection:

SimPO: Simplest, best performance, no reference model
DPO: Need reference model baseline, more conservative
PPO: Maximum control, need reward model, complex setup
GRPO: Memory-efficient RL, no critic

Use alternatives instead:

OpenRLHF: Multi-node distributed training, PPO/GRPO
TRL: Need multiple methods in one framework
DPO: Established baseline comparison

Common issues

Issue: Loss divergence Reduce learning rate:

learning_rate: 3e-7  # Reduce from 5e-7

Reduce beta:

beta: 1.0  # Reduce from 2.0

Issue: Model forgets capabilities Add SFT regularization:

sft_weight: 0.1  # Add SFT loss component

Issue: Poor preference separation Increase beta and margin:

beta: 5.0            # Increase from 2.0
gamma_beta_ratio: 0.8  # Increase from 0.5

Issue: OOM during training Reduce batch size:

per_device_train_batch_size: 1
gradient_accumulation_steps: 16  # Maintain effective batch

Enable gradient checkpointing:

gradient_checkpointing: true

Advanced topics

Loss functions: See references/loss-functions.md for sigmoid vs hinge loss, mathematical formulations, and when to use each. Hyperparameter tuning: See references/hyperparameters.md for beta, gamma, learning rate selection guide, and model-size-specific recommendations. Dataset preparation: See references/datasets.md for preference data formats, quality filtering, and custom dataset creation.

Hardware requirements

GPU: NVIDIA A100/H100 recommended
VRAM:
- 7B model: 1× A100 40GB (DeepSpeed ZeRO-3)
- 8B model: 2× A100 40GB
- 70B model: 8× A100 80GB
Single-node: DeepSpeed ZeRO-3 sufficient
Mixed precision: BF16 recommended

Memory optimization:

DeepSpeed ZeRO-3 (default config)
Gradient checkpointing
Flash Attention 2

Resources

Paper: https://arxiv.org/abs/2405.14734 (NeurIPS 2024)
GitHub: https://github.com/princeton-nlp/SimPO
Models: https://huggingface.co/princeton-nlp
Alignment Handbook: https://github.com/huggingface/alignment-handbook

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Simpo — Reference-free preference alignment, simpler than DPO

Skill metadata

Reference: full SKILL.md

SimPO - Simple Preference Optimization

Quick start

Common workflows

Workflow 1: Train from base model (Mistral 7B)

Workflow 2: Fine-tune instruct model (Llama 3 8B)

Workflow 3: Reasoning-intensive tasks (lower LR)

When to use vs alternatives

Common issues

Advanced topics

Hardware requirements

Resources

​Skill metadata

​Reference: full SKILL.md

​SimPO - Simple Preference Optimization

​Quick start

​Common workflows

​Workflow 1: Train from base model (Mistral 7B)

​Workflow 2: Fine-tune instruct model (Llama 3 8B)

​Workflow 3: Reasoning-intensive tasks (lower LR)

​When to use vs alternatives

​Common issues

​Advanced topics

​Hardware requirements

​Resources

Skill metadata

Reference: full SKILL.md

SimPO - Simple Preference Optimization

Quick start

Common workflows

Workflow 1: Train from base model (Mistral 7B)

Workflow 2: Fine-tune instruct model (Llama 3 8B)

Workflow 3: Reasoning-intensive tasks (lower LR)

When to use vs alternatives

Common issues

Advanced topics

Hardware requirements

Resources