QuIP: Quantization with Incoherence Processing

This repository contains code for the paper QuIP: 2-Bit Quantization of Large Language Models with Guarantees.

TLDR: Our proposed incoherence processing enables quantization of large language models down to 2 bits. Please see our paper for full details.

The code is built on top of QuIP, GPTQ, and GPTQ-for-LLaMA. The current code includes the following:

Language Generation

# Compute full precision (FP16) results
CUDA_VISIBLE_DEVICES=0 python llama.py meta-llama/llama-2-7b-hf c4
# Run a quantization method with Incoherence Processing
CUDA_VISIBLE_DEVICES=0 python llama.py meta-llama/llama-2-7b-hf c4 --wbits 4 --quant <quantmethod> --incoh_processing --save <savename>
# Run a quantization method with baseline processing
CUDA_VISIBLE_DEVICES=0 python llama.py meta-llama/llama-2-7b-hf c4 --wbits 4 --quant gptq --pre_gptqH --save <savename>

Quantization methods include:

• ldlq: runs the LDLQ rounding algorithm (we show its equivalence to GPTQ, providing a novel theoretical analysis)
• ldlqRG: runs the LDLQ_RG algorithm with additional hessian-based hessian reordering, and further greedy updates, with --npasses controlling the number of passes over the weights
• gptq: runs GPTQ algorithm as implemented by its authors
• allbal: algorithm to run greedy updates by themselves, with --npasses the argument controlling the number of passes over the weights
• ldlbal_admm: alternative algorithm which constraints the rounded weights to be sufficiently close to their original, giving a better theoretical bound.

The --incoh_processing argument is a meta argument which sets the following flags --pre_gptqH --pre_rescale --pre_proj --qfn b. For more control into the pre and post processing, these arguments can be set individually.

To run other Llama models replace llama-2-7b-hf with the other size variants. On larger models, a low compute-to-memory-access ratio can slow down the quantization algorithms. We implement a lazy batch update to te weight matrix specified by --lazy_batch. This argument works with the quantization methods {ldlq, ldlqRG, allbal}. Note GPTQ already implements this, and is where we got the idea from.

GPTQ and LDLQ Equivalence

Run the following script to empirically verify that the output of GPTQ's implemenation and our implemenation of LDLQ are identical: python gptq_ldlq_equiv.py. Note GPTQ's implementation requires running on a GPU.

GTPQ/LDLQ Finite Grid Counterexample

Run python gptq_counter.py to compute the proxy loss of our W,H counterexample.

Computing Proxy Loss

In a similar manner to llama.py, run llama_saveH.py to save the H matrices resulting from the specified model and quantization method. Then, run llama_proxy.py to compute the proxy loss for a specified quantization method.

CUDA_VISIBLE_DEVICES=0 python llama_proxy.py c4 --wbits 4 --quant <quant_method>

H Summary

Run the following script to compute summary statistics of a folder <dirname> of H matrices, output from running llama_saveH.py.

python compute_Hsummary.py --dirname <> --savename <>