opt-125m-mlx-4bit

4-bit MLX conversion of facebook/opt-125m optimized for Apple Silicon native GPU inference.

Converted by: SirSahOl
Source Model: facebook/opt-125m
Framework: MLX by Apple
Quantization: 4-bit (Average 4.50 bits per weight)
Format: safetensors
License: other


Model Details

  • Architecture: OPTForCausalLM
  • Parameters: 125M
  • Context Length: 2,048 tokens
  • Format: MLX (Apple Silicon native GPU format)
  • Quantization: 4-bit (Average 4.50 bits per weight)
  • Active VRAM Footprint: ~122 MB (Minimum recommended: 8 GB Unified Memory)

Quick Start

Installation

pip install mlx-lm

Usage

CLI

# Chat interactively
mlx_lm.chat --model SirSahOl/opt-125m-chat-mlx-4bit

# Generate text
mlx_lm.generate --model SirSahOl/opt-125m-chat-mlx-4bit --prompt "Write a short poem about artificial intelligence."

Python API (with Chat Template)

from mlx_lm import load, generate

model, tokenizer = load("SirSahOl/opt-125m-chat-mlx-4bit")

messages = [
    {"role": "user", "content": "Explain quantum superposition in simple terms."}
]
prompt = tokenizer.apply_chat_template(
    messages, tokenize=False, add_generation_prompt=True
)

response = generate(model, tokenizer, prompt=prompt, verbose=True)
print(response)

Performance Benchmarks

Measured Benchmarks (Apple M1)

Metric 4-bit 8-bit 16-bit
Tokens/sec 360.69 264.13 60.9
TTFT 2.79 ms 3.8 ms 16.44 ms
Peak Memory 234.4 MB 335.8 MB 316.7 MB

Benchmarked on Apple M1 with 8GB unified memory. Average over 5 runs with 256 max tokens.


Multi-Quantization Comparison

Evaluate your hardware budget and choose the optimal precision:

Variant Disk Size VRAM Footprint Target Apple Silicon Hardware Key Advantage
4-bit MLX (This Repository) ~79 MB ~119 MB M1 / M2 / M3 / M4 (8GB+ Unified Memory) Ultra-compact footprint, maximum generation speed; negligible memory pressure.
8-bit MLX ~146 MB ~191 MB M1 / M2 / M3 / M4 (8GB+ Unified Memory) Near-lossless precision with an extremely lightweight footprint.
16-bit MLX ~270 MB ~340 MB M1 / M2 / M3 / M4 (8GB+ Unified Memory) Full unquantized precision; zero perplexity penalty for reference evaluation.

Who Should Use This?

Your Hardware Recommended Quantization
M1/M2/M3/M4 (8GB – 16GB) 4-bit β€” Best balance of speed, low memory, and multitasking capability
M1/M2/M3/M4 Pro/Max (18GB – 36GB) 8-bit β€” Higher quality reasoning with comfortable memory headroom
M1/M2/M3/M4 Max/Ultra (36GB – 192GB) 16-bit β€” Unquantized full precision, zero quality degradation

General guidance:

  • Use 4-bit if you want to run this model alongside IDEs, browsers, and background development tools.
  • Use 8-bit if you have 16GB+ unified memory and require superior reasoning and code accuracy.
  • Use 16-bit for research, benchmarking, evaluation, or high-end workstation deployments.

Other Quantization Variants


LM Studio & Local Inference Setup Guide

To prevent runaway loops and ensure correct conversational turn-taking, configure custom stop tokens in your local inference runtime:

  1. <|im_start|>
  2. <|im_end|>
  3. <|endoftext|>

Prompt Template Formatting

  • System Prefix: <|im_start|>system\n
  • System Suffix: <|im_end|>\n
  • User Prefix: <|im_start|>user\n
  • Assistant Suffix: <|im_end|>\n<|im_start|>assistant\n

Ollama Quickstart

FROM SirSahOl/opt-125m-chat-mlx-4bit
PARAMETER stop "<|im_start|>"
PARAMETER stop "<|im_end|>"
PARAMETER stop "<|endoftext|>"
PARAMETER temperature 0.7
ollama create opt-125m-chat-mlx-4bit -f Modelfile
ollama run opt-125m-chat-mlx-4bit

Conversion Details


Limitations & Known Issues

  • 4-bit group-wise quantization introduces minor precision loss compared to unquantized weights; for deep mathematical derivations or precision-critical reasoning, test the 8-bit or 16-bit variants.
  • High context sequences (>32K tokens) require sufficient unified memory headroom; ensure unified memory is not overcommitted.
  • This is a weight-only MLX conversion designed specifically for Apple Silicon GPUs (M1/M2/M3/M4 series).

License

This model conversion inherits the license of the source model: other.

See the original model card for full license details.


Changelog

Version Date Changes
v1.0 N/A Initial conversion

Converted with MLX Foundry β€” a professional pipeline for converting models to Apple MLX format.

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