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openbmb/
BitCPM-CANN-0.5B

Name: BitCPM-CANN-0.5B
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GitHub Repo | Technical Report

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Introduction

BitCPM-CANN is the first end-to-end 1.58-bit (ternary) large language model training system natively built on Huawei Ascend NPU. The system integrates quantization-aware training (QAT) into the Megatron-LM framework with MindSpeed acceleration, covering the full training stack from custom ternary operators to distributed parallel training on Ascend 910B.

We train a family of four models—BitCPM-CANN-0.5B/1B/3B/8B—and evaluate them against their full-precision MiniCPM4 counterparts across 11 benchmarks. The 1B/3B/8B models retain 95.7%–97.2% of full-precision performance, while enabling approximately 6× memory reduction at inference time. QAT introduces only 5% training throughput overhead (148 vs. 155 TFLOP/s per NPU).

Key Features

🔬 1.58-Bit Ternary Quantization: Compresses model weights to ternary values {-1, 0, 1}, achieving ~90% bit-width reduction compared to BF16.
🖥️ Native Ascend NPU Training: First publicly reported 1.58-bit training effort on domestic NPU platform at 8B scale, establishing reusable low-bit training infrastructure for the Ascend ecosystem.
⚡ Minimal Training Overhead: Only 5% throughput degradation compared to full-precision training on Ascend 910B.
📦 ~6× Inference Memory Reduction: Enables longer contexts, more serving replicas, and edge deployment on consumer devices.

Important Note

The models in this repository are in pseudo-quantized (fake quantization) format. This means the weights are stored in standard floating-point format with ternary values already applied during training. You can load and run inference with these models exactly the same way as full-precision models—no special quantization libraries or custom kernels are required.

BitCPM-CANN Model Family

Model	HuggingFace	GGUF
BitCPM-CANN-0.5B	openbmb/BitCPM-CANN-0.5B	openbmb/BitCPM-CANN-0.5B-gguf
BitCPM-CANN-1B	openbmb/BitCPM-CANN-1B	openbmb/BitCPM-CANN-1B-gguf
BitCPM-CANN-3B	openbmb/BitCPM-CANN-3B	openbmb/BitCPM-CANN-3B-gguf
BitCPM-CANN-8B	openbmb/BitCPM-CANN-8B	openbmb/BitCPM-CANN-8B-gguf

Usage

Inference with Transformers

Since BitCPM-CANN models are in pseudo-quantized format, you can use them exactly like standard full-precision models:

python

from transformers import AutoModelForCausalLM, AutoTokenizer
import torch
torch.manual_seed(0)

path = 'openbmb/BitCPM-CANN-0.5B'
device = "cuda"
tokenizer = AutoTokenizer.from_pretrained(path)
model = AutoModelForCausalLM.from_pretrained(path, torch_dtype=torch.bfloat16, device_map=device, trust_remote_code=True)

# User can directly use the chat interface
responds, history = model.chat(tokenizer, "Write an article about Artificial Intelligence.", temperature=0.7, top_p=0.7)
print(responds)

# User can also use the generate interface
# messages = [
#     {"role": "user", "content": "Write an article about Artificial Intelligence."},
# ]
# prompt_text = tokenizer.apply_chat_template(
#     messages,
#     tokenize=False,
#     add_generation_prompt=True,
# )
# model_inputs = tokenizer([prompt_text], return_tensors="pt").to(device)

# model_outputs = model.generate(
#     **model_inputs,
#     max_new_tokens=1024,
#     top_p=0.7,
#     temperature=0.7
# )
# output_token_ids = [
#     model_outputs[i][len(model_inputs[i]):] for i in range(len(model_inputs['input_ids']))
# ]

# responses = tokenizer.batch_decode(output_token_ids, skip_special_tokens=True)[0]
# print(responses)

Evaluation Results

Main Results

BitCPM-CANN models are evaluated against their full-precision MiniCPM4 counterparts across 11 benchmarks spanning commonsense reasoning, domain knowledge, and mathematics & reasoning.

Task	8B FP	8B Ternary	3B FP	3B Ternary	1B FP	1B Ternary	0.5B FP	0.5B Ternary
ARC-c	87.46	86.10	80.34	78.98	64.41	67.12	51.86	50.51
ARC-e	95.06	93.47	92.77	88.36	79.89	79.01	71.78	65.08
BoolQ	84.89	83.39	79.85	77.89	68.38	65.50	62.29	43.55
PIQA	80.52	78.78	70.57	72.69	66.16	65.45	60.99	58.49
WinoGrande	63.30	61.17	58.41	52.96	51.62	53.28	51.07	51.54
CMMLU	80.62	78.92	78.11	76.53	74.57	67.42	65.22	60.49
C-Eval	81.36	77.50	75.85	75.89	73.25	65.96	66.11	60.74
MMLU	75.83	70.65	66.95	64.41	57.71	57.71	55.55	50.73
MMLU-Redux	77.14	69.85	65.82	60.07	54.80	54.16	48.00	43.79
BBH	76.72	70.70	68.29	68.30	64.40	60.40	49.87	47.44
GSM8K	91.51	85.75	81.64	79.45	63.15	61.56	52.08	39.42
Average (11 tasks)	81.31	77.84	74.42	72.32	65.30	63.42	57.71	51.98
Retention		95.7%		97.2%		97.1%		90.1%

Key Observations

1B and above achieve ≥95.7% retention: The 3B model achieves the highest retention at 97.2%, demonstrating that ternary QAT at this scale introduces minimal capability loss.
0.5B reveals scale-dependent sensitivity: The smallest model retains 90.1%, indicating that quantization perturbation is more damaging when model capacity is limited.
1:1 alignment with MiniCPM4: The matched evaluation enables direct substitution decisions—deployments can replace specific full-precision models with their ternary counterparts with clearly quantified trade-offs.

Training Efficiency

Configuration	TFLOP/s per NPU	Overhead
Full-precision	155	—
Ternary QAT	148	4.5%

System-level throughput on 2-node 16-card Ascend 910C:

3B model: ~2700 tokens/s per card
8B model: ~1340 tokens/s per card

Technical Approach

BitCPM-CANN uses a ternary quantizer that maps each weight group to {-1, 0, 1} scaled by a group-wise factor, trained with Straight-Through Estimator (STE) for gradient flow. The training follows a two-stage strategy: complete QAT followed by post-training distillation, which avoids amplifying training instability during early training.

The system is built as a four-layer vertical stack on Ascend NPU:

QAT Training Logic: Ternary quantizer with STE, pluggable quantization layers in Megatron-LM.
Megatron-LM Quantized Model Layer: Tensor-parallel linear layers with integrated weight/activation quantizers.
Framework Entry Layer: torch_npu and mindspeed.megatron_adaptor injection for NPU execution.
Ascend Software-Hardware Stack: MindSpeed, CANN, HCCL communication, Ascend 910B NPU hardware.

For full technical details, please refer to our Technical Report.

Statement

As a language model, BitCPM-CANN generates content by learning from a vast amount of text.
However, it does not possess the ability to comprehend or express personal opinions or value judgments.
Any content generated by BitCPM-CANN does not represent the viewpoints or positions of the model developers.
Therefore, when using content generated by BitCPM-CANN, users should take full responsibility for evaluating and verifying it on their own.

LICENSE

This repository and BitCPM-CANN models are released under the Apache-2.0 License.

Citation

Please cite our technical report if you find our work valuable.

bibtex

@article{bitcpmcann,
  title={{BitCPM-CANN}: Native 1.58-Bit Large Language Model Training on Ascend NPU},
  author={BitCPM Team},
  year={2026}
}