BitBLAS

BitBLAS is a library to support mixed-precision BLAS operations on GPUs, for example, the $W_{wdtype}A_{adtype}$ mixed-precision matrix multiplication where $C_{cdtype}[M, N] = A_{adtype}[M, K] \times W_{wdtype}[N, K]$. BitBLAS aims to support efficient mixed-precision DNN model deployment, especially the $W_{wdtype}A_{adtype}$ quantization in large language models (LLMs), for example, the $W_{UINT4}A_{FP16}$ in GPTQ, the $W_{INT2}A_{FP16}$ in BitDistiller, the $W_{INT2}A_{INT8}$ in BitNet-b1.58. BitBLAS is based on techniques from our paper "Ladder: Enabling Efficient Low-Precision Deep Learning Computing through Hardware-aware Tensor Transformation" at OSDI'24.

Some of the key features of BitBLAS include:

• High performance matrix multiplication for both GEMV (e.g., the single batch auto-regressive decode phase in LLM) and GEMM (e.g., the batched auto-regressive decode phase and the prefill phase in LLM):
  • $W_{wdtype}A_{adtype}$ mixed-precision matrix multiplication including FP16xFP8/FP4/INT4/2/1, INT8xINT4/2/1, etc. Please checkout support matrix for detailed data types support.
  • Matrix multiplication like FP16xFP16 and INT8xINT8.
• Auto-Tensorization for TensorCore-like hardware instructions.
• Implemented integration to PyTorch, GPTQModel, AutoGPTQ, vLLM and BitNet-b1.58 for LLM deployment. Please checkout benchmark summary for detailed end2end LLM inference performance.
• BitBLAS first implemented $W_{INT2}A_{INT8}$ GEMV/GEMM in BitNet-b1.58 with 8x/2x speedup over cuBLAS $W_{FP16}A_{FP16}$ on A100, please checkout op_benchmark_a100_int2_scaling for detailed benchmark results. Please checkout BitNet-b1.58 integration for the integration with the 3rdparty reproduced BitNet-b1.58 model.
• Support customizing mixed-precision DNN operations for your specific scenarios via the flexible DSL (TIR Script).

Latest News

• 08/12/2024 🚀🚀: We've improved performance for contiguous batching. To enable it, you'll need to set specific flags. For more details, please refer to PR #133.
• 07/11/2024 ✨: Ladder is published and presented in OSDI'24. Please find Ladder paper and presentation if you are interested in the technical details of BitBLAS.
• 06/25/2024 🚀🚀: BitBLAS has been integrated into GPTQModel! You can now use BitBLAS as a backend in GPTQ.
• 05/04/2024 🚀🚀: We’ve added integration examples for the 1.58-bit model! Check out the files under integration/BitNet.
• 04/30/2024 🚀🚀: BitBLAS now supports FP8 TensorCore ($W_{E5M2/E4M3}A_{E4M3/E5M2}$), providing more combinations beyond the three available in cuBLAS!
• 04/19/2024 ✨: We are excited to announce that BitBLAS, a high-performance library for mixed-precision DNN model deployment, is now open source and available to the public!

Integration Example of FasterTransformer with BitBLAS

Benchmark Summary

BitBLAS achieves exceptional performance across a variety of computational patterns. Below are selected results showcasing its capabilities:

• End2End Integration with Quantize Inference Kernel for AutoGPTQ and vLLM.

  

• Weight Only Matmul performance on A100

  

• TensorCore FP16/INT8 GEMM Performance Vs. Vendor Library on A100 and RTX4090

  

For more detailed information on benchmark sets with other formats (NF4/FP4) and other devices (RTX 3090), please refer to the benchmark.

Support Matrix

A_dtype	W_dtype	Accum_dtype	Out_dtype	BitBLAS Support	Tested Platform
BF16	BF16	FP32	FP16	√	A100(SM_80)/A6000(SM_86)
BF16	FP4_E2M1	FP32	FP16	√	A100(SM_80)/A6000(SM_86)
BF16	FP8_E4M3	FP32	FP16	√	A100(SM_80)/A6000(SM_86)
BF16	INT8	FP32	FP16	√	A100(SM_80)/A6000(SM_86)
BF16	UINT4/INT4	FP32	FP16	√	A100(SM_80)/A6000(SM_86)
BF16	UINT2/INT2	FP32	FP16	√	A100(SM_80)/A6000(SM_86)
BF16	UINT1	FP32	FP16	√	A100(SM_80)/A6000(SM_86)
BF16	NF4	FP32	FP16	√	A100(SM_80)/A6000(SM_86)
FP16	FP16	FP32/FP16	FP16	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
FP16	FP4_E2M1	FP32/FP16	FP16	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
FP16	FP8_E4M3	FP32/FP16	FP16	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
FP16	INT8	FP32/FP16	FP16	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
FP16	UINT4/INT4	FP32/FP16	FP16	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
FP16	UINT2/INT2	FP32/FP16	FP16	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
FP16	UINT1	FP32/FP16	FP16	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
FP16	NF4	FP32/FP16	FP16	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
INT8	INT8	INT32	FP32/INT32/FP16/INT8	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
INT8	UINT4/INT4	INT32	FP32/INT32/FP16/INT8	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
INT8	UINT2/INT2	INT32	FP32/INT32/FP16/INT8	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
INT8	UINT1	INT32	FP32/INT32/FP16/INT8	√	V100(SM_70)/A100(SM_80)/A6000(SM_86)/RTX 4090(SM_89)
FP8_E4M3	FP8_E4M3	FP32	FP32/FP16	√	RTX 4090(SM_89)
FP8_E5M2	FP8_E5M2	FP32	FP32/FP16	√	RTX 4090(SM_89)

We are continuously expanding the support matrix. If you have any specific requirements, please feel free to open an issue or PR.

Getting Started with an Example

Installing with pip

Prerequisites for installation via wheel or PyPI

• Operating System: Ubuntu 20.04 or later
• Python Version: >= 3.8
• CUDA Version: >= 11.0

The easiest way to install BitBLAS is direcly from the PyPi using pip. To install the latest version, run the following command in your terminal.

pip install bitblas

Alternatively, to install the latest version of BitBLAS from the github repository, you can run the following command:

pip install git+https://github.com/microsoft/BitBLAS.git

After installing BitBLAS, you can verify the installation by running:

python -c "import bitblas; print(bitblas.__version__)"  

Note: Currently, BitBLAS whl is only supported on Ubuntu 20.04 or later version as we build the whl files on this platform. Currently we only provide whl files for CUDA>=11.0 and with Python>=3.8. If you are using a different platform or environment, you may need to build BitBLAS from source. More installation methods can be found in the installation document.

Example: $W_{INT4}A_{FP16}$ mixed-precision matrix multiplication

BitBLAS provides two Python APIs to perform mixed-precision matrix multiplication:

• bitblas.Matmul implements the $W_{wdtype}A_{adtype}$ mixed-precision matrix multiplication of $C_{cdtype}[M, N] = A_{adtype}[M, K] \times W_{wdtype}[N, K]$ where $W_{wdtype}$ indicates the weight of $wtype$, A_{adtype} indicates the activation of $adtype$, and C_{cdtype} indicates the output of $cdtype$.
• bitblas.Linear is a PyTorch nn.Linear-like module to support a Linear of mixed-precision.

Here is an example for a $W_{INT4}A_{FP16}$ mixed-precision matrix multiplication: $out_{FP16}[M, N] = A_{FP16}[M, K] \times W_{INT4}[N, K]$, this example includes the creation of input matrices, quantization of weight matrices, and execution of the matrix multiplication with the bitblas.Matmul API. The result is then compared against a reference result obtained through conventional methods to ensure accuracy.

import bitblas
import torch

# uncomment to enable debug output
# bitblas.set_log_level("Debug")

matmul_config = bitblas.MatmulConfig(
    M=1,  # M dimension
    N=2048,  # N dimension
    K=1024,  # K dimension
    A_dtype="float16",  # activation A dtype
    W_dtype="int4",  # weight W dtype
    accum_dtype="float16",  # accumulation dtype
    out_dtype="float16",  # output dtype
    layout="nt",  # matrix layout, "nt" indicates the layout of A is non-transpose and the layout of W is transpose
    with_bias=False,  # bias
    # configs for weight only quantization
    group_size=None,  # setting for grouped quantization
    with_scaling=False,  # setting for scaling factor
    with_zeros=False,  # setting for zeros
    zeros_mode=None,  # setting for how to calculating zeros
)

matmul = bitblas.Matmul(config=matmul_config)

# Create input matrices
input_tensor = torch.rand((1, 1024), dtype=torch.float16).cuda()
weight_tensor = torch.randint(0, 7, (2048, 1024), dtype=torch.int8).cuda()

# Transform weight tensor to int4 data type
weight_tensor_int4 = matmul.transform_weight(weight_tensor)

# Perform mixed-precision matrix multiplication
output_tensor = matmul(input_tensor, weight_tensor_int4)

# Reference result using PyTorch matmul for comparison
ref_result = torch.matmul(input_tensor, weight_tensor.t().to(torch.float16))
# Assert that the results are close within a specified tolerance, note that the int4 randint value is a little bigger than the float16 value, so we set the atol to 1.0
print("Ref output:", ref_result)
print("BitBLAS output:", output_tensor)
torch.testing.assert_close(output_tensor, ref_result, rtol=1e-2, atol=1e-0)

Note: More examples can be found in the QuickStart document.

Documents

• Installation: The installation document of BitBLAS. Make sure you already have the cuda toolkit (version >= 11.0) installed in the system.

  • You can easily install from pip install bitblas from PyPi. Currently we only provide whl files for CUDA>=11.0 and Ubuntu>=20.04 with Python>=3.8, if you are using a different version of CUDA or OS environment, you may need to build BitBLAS from source.

• QuickStart: This document provides examples to use BitBLAS in your program with bitblas.Matmul and bitblas.Linear.

• Python API: The Python API document of BitBLAS. BitBLAS provides two Python APIs to perform mixed-precision matrix multiplication:

  • bitblas.Matmul implements the $W_{wdtype}A_{adtype}$ mixed-precision matrix multiplication of $C_{cdtype}[M, N] = A_{adtype}[M, K] \times W_{wdtype}[N, K]$.
  • bitblas.Linear is a PyTorch nn.Linear-like module to support a Linear of mixed-precision.

• Integration: Explore how BitBLAS seamlessly integrates with LLM deployment frameworks through our examples. Discover the ease of integrating BitBLAS with PyTorch, AutoGPTQ, and vLLM in the 3rd-party integration examples.

• Customization: BitBLAS supports implementing customized mixed-precision DNN operations (e.g., Conv2D) rather than matrix multiplication with the flexible DSL (TIR Script).

Reference

Please cite BitBLAS/Ladder in your publications if it helps your research:

@inproceedings {ladder-osdi24,
author = {Lei Wang and Lingxiao Ma and Shijie Cao and Quanlu Zhang and Jilong Xue and Yining Shi and Ningxin Zheng and Ziming Miao and Fan Yang and Ting Cao and Yuqing Yang and Mao Yang},
title = {Ladder: Enabling Efficient Low-Precision Deep Learning Computing through Hardware-aware Tensor Transformation},
booktitle = {18th USENIX Symposium on Operating Systems Design and Implementation (OSDI 24)},
year = {2024},
isbn = {978-1-939133-40-3},
address = {Santa Clara, CA},
pages = {307--323},
url = {https://www.usenix.org/conference/osdi24/presentation/wang-lei},
publisher = {USENIX Association},
month = jul
}

Contributing

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