Customizing Language Models with Instance-wise LoRA for Sequential Recommendation

Sequential recommendation systems predict the next interaction item based on users' past interactions, aligning recommendations with individual preferences. Leveraging the strengths of Large Language Models (LLMs) in knowledge comprehension and reasoning, recent approaches are eager to apply LLMs to sequential recommendation. A common paradigm is converting user behavior sequences into instruction data, and fine-tuning the LLM with parameter-efficient fine-tuning (PEFT) methods like Low-Rank Adaption (LoRA). However, the uniform application of LoRA across diverse user behaviors is insufficient to capture individual variability, resulting in negative transfer between disparate sequences. To address these challenges, we propose Instance-wise LoRA (iLoRA). We innovatively treat the sequential recommendation task as a form of multi-task learning, integrating LoRA with the Mixture of Experts (MoE) framework. This approach encourages different experts to capture various aspects of user behavior. Additionally, we introduce a sequence representation guided gate function that generates customized expert participation weights for each user sequence, which allows dynamic parameter adjustment for instance-wise recommendations. In sequential recommendation, iLoRA achieves an average relative improvement of 11.4\% over basic LoRA in the hit ratio metric, with less than a 1\% relative increase in trainable parameters. Extensive experiments on three benchmark datasets demonstrate the effectiveness of iLoRA, highlighting its superior performance compared to existing methods in mitigating negative transfer and improving recommendation accuracy. Our data and code are available at https://github.com/AkaliKong/iLoRA.

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Peer review

Reviewer wwLq7/10 · confidence 4/52024-07-05

Summary

Sequential recommendations is well studied problem with impact across industries which try to personalise a users experience based on their past interactions. Recent popularity of LLMs has led to a lot of research into their use for this task through various generation methodologies. One of those methods is the use of LoRA to adapt the LLM to a specific data distribution (i.e. dataset) leading to better recommendations but it has been shown that due to the high variability in the sequences being input it is often hard to capture all kinds of patterns. This leads to negative transfer of information - to solve which the authors propose a method called iLoRA which is really MoE meets LoRA. Instead of a single LoRA module they propose having multiple LoRA "experts" with the motivation that they will capture different kinds of patterns and information in them. To combine the output from these experts they use an "attention"-like gating mechanism that looks at the input sequence embeddings (created using existing techniques) and computes a softmax to get the weight of each expert to be considered. The paper contains extensive experimentation to prove out the ideas and contributions and validate the motivation behind the idea. The metrics show that this approach is better than the other SoTA comparable methods in industry.

Strengths

The paper is written clearly, is easy to follow and explains the key ideas that inspired and led to the approach described. The experiments conducted (including ablation studies) provide sufficient evidence to prove the claims and contributions. The paper is able to take key concepts (MoE, Attention, LoRA, item recommendations) in research and combine them in a new way to solve a problem like sequential recommendation which is significant across many industries. The results on the metrics being used by the paper outperform other SoTA techniques which proves out the significance for industry use. The performance gain is also demonstrated across 3 popular datasets which gives it authenticity. The idea is original albeit similar techniques are present in research where people have either tried to a weighted sum of multiple LoRA's or swap them out at runtime based on a gating mechanism. Although I haven't seen an application in recommendation systems yet.

Weaknesses

The authors should have shown the contribution by expanding to more metrics - at the least HitRate@K, but also metrics like NDCG@K. These are very common metrics in the recommendation space and provide a more holistic view of the output quality. The novelty in the paper is limited as it combines common research ideas in a not so unique way. Also, the impact of training data size on the model performance was not studied - recommendation models can be heavily dependent on this due to the generic sparse nature of data so this analysis would give more weight and significance to the paper. I would have liked to understand more on the out of domain abilities of such a model and also specific abilities on cold start recommendations - which is a big challenge in this space. This was not discussed.

Questions

1. Did you do any comparisons with the idea of training multiple full LoRA's and then doing a weighted sum of them OR swapping them based on instance embeddings ? 2. Other than the overall metrics did you do any analysis on performance when the data is sparse , or situations of cold start recommendations ?

Rating

7

Confidence

4

Soundness

4

Presentation

4

Contribution

3

Limitations

The authors have discussed the major limitations. The impact of invalid outputs due to the generative approach was not discussed in detail - this could have potential risks.

Reviewer 7niz4/10 · confidence 4/52024-07-12

Summary

The author focus on extend sequential recommendation task with the help of large language models. The author proposed instance-wise LoRA and integrate with mixture of experts framework to capture specific interests of user preferences. Experiments results on two benchmark datasets demonstrate the effectiveness of proposed model.

Strengths

1. The authors proposed iLoRA for sequential recommendation task, which address previous works failing to capture individual variability. It creates a diverse array of experts and captures specific aspects of user preferences, guiding the gating network to output customized expert participation weights. 2. Extensive experiments on two benchmark datasets demonstrate the effectiveness of iLoRA. The ablation studies clearly show that every part of the proposed model makes sense. 3. The paper is well-written. Figures and tables are very clear and easy to read.

Weaknesses

See Questions to authors.

Questions

. How do you partition the sequence data into 8 clusters? Clustering by calculating Euclidean distance of what? is the output embeddings of SASRec? Explain why you do that. 2. I think that the proposed mod framework in this manuscript is kind of like the soft-attention mechanism with some parameters having shared weights. What are the in-depth or essential differences between the proposed MoE framework and the soft-attention mechanisms? 3. Lacks further analysis in ablation study section 4.3. The authors just repeat the results that have shown in figures. For example, 4-experts can achieve the optimal performance and 8-experts reduce it. Why? With fewer training epochs, 8-experts outperforms, but it cannot keep it while training epochs increase. Is it because of the hidden dimension r of LoRA that limits the performance of more experts? 4. The writing language can be further checked, since there are minor language mistakes such as nvidia-smi a100.

Rating

4

Confidence

4

Soundness

3

Presentation

3

Contribution

2

Limitations

The author explains the limitations of the model constructed in the article, such as the recommendation strategy and universality that still need to be explored.

Authorsrebuttal2024-08-13

Dear Reviewer, Thank you very much for your valuable and constructive feedback. We greatly appreciate the time and effort you have put into providing us with these insights, which have significantly helped us in refining our paper. Regarding your primary concern about **experimental details and motivation**, we have provided additional discussion and clarification. For the point you raised about the **Lack of clear distinction from the soft attention mechanism**, we have thoroughly explained the differences and advantages of our proposed iLoRA framework compared to the soft attention mechanism. Additionally, we have included an experiment demonstrating the performance benefits of iLoRA over soft attention routing in **Figure 2** in one-page uploaded pdf. Concerning the **Lack of further analysis in the ablation study**, we have added a detailed analysis following your suggestion. We also have throughly examined the linguistic concerns raised and will make the appropriate revisions in the final version. Thank you once again for your suggestions, and we hope that our response effectively addresses your concerns! We truly appreciate your support, encouragement, and understanding. Best regards, Authors

Reviewer 59LV7/10 · confidence 3/52024-07-19

Summary

The paper introduces iLoRA, which combines LoRA with user representation-guided mixture of expert architecture. The motivation is clear and the writing is good. Extensive experiments are conducted on three public datasets, demonstrating the performance of the proposed method.

Strengths

1. Timely study on large language models and sequential recommendation. 2. The motivation of the proposed method, i.e., should be more personalized LoRA parameters, is clear and convincing. 3. The writing is good and the paper is easy to follow. 4. Experiments are conducted on three public datasets, demonstrating the performance of the proposed iLoRA technique. 5. Code is available during the reviewing phase. === Update After the Rebuttal Phase === The rebuttal includes new results and clarifications, which are helpful in addressing my concerns. In recent days, I also conducted experiments using the provided code, and the results further verify the paper’s conclusions. As a result, I will raise my rating and vote for acceptance.

Weaknesses

1. The evaluation setting is kind of fragile. For each input sequence, only 20 candidate items are randomly selected as negative samples. In this setting, the results may be influenced a lot by randomness. In addition, if the proposed method only applies to a candidate size of 20 items, the value of this work to the real recommender systems can be doubted. 2. References of MoE are limited. The related works about MoE are quite concise. The author(s) are encouraged to discuss more about how MoE is applied to LLMs and recommendation models. 3. Presentation issues. 1. Lines 554 - 562 and lines 563 - 570 are duplicated. 2. Figure 3 (c) is suggested to be replaced by a vector graph to make it more clear.

Questions

Please find the details in "Weaknesses".

Rating

7

Confidence

3

Soundness

4

Presentation

4

Contribution

3

Limitations

N/A

Reviewer cnYP5/10 · confidence 3/52024-07-25

Summary

The paper addresses the challenge of personalizing language models for sequential recommendation tasks, where user behaviors exhibit significant individual variability. The proposed solution, Instance-wise LoRA (iLoRA), adapts the mixture of experts concept to tailor LLMsfor this variability.

Strengths

The iLoRA framework proposes splitting the standard LoRA module into multiple experts, each capturing specific aspects of user behavior. Key components of this solution include: - Splitting Low-Rank Matrices into Experts: Dividing the projection matrices into an array of experts to capture different aspects of user preferences. - Instance-wise Attentions: Using a gating network to generate attention scores for each expert based on the user's historical item sequence. This customization helps in adapting the model more accurately to individual user behaviors. - Fine-tuning with Hybrid Prompting: Applying the personally-activated LoRA to fine-tune the LLM, thus mitigating negative transfer and enhancing the model's adaptability. The solution leverages the mixture of experts approach to ensure scalability and efficiency, maintaining the same total number of parameters as the standard LoRA to avoid overfitting. The starting point of the article's issue is reasonable, and personalized LoRA is an impressive idea.

Weaknesses

# - The technical contribution of the paper is insufficient. For example, simply splitting the low-rank matrices into multiple experts representing different aspects seems inadequate and has room for expansion. It could be more refined by setting the number of experts based on different user clusters and controlling the low-rank size of the corresponding experts according to the number of users in each category. - The paper proposes a framework rather than a model. However, in the main experiments, the authors compare it with numerous models instead of fine-tuning-based methods, which is puzzling. Additionally, the framework proposed in the paper seems to be a general one, or are there any challenges that limit it to sequential recommendation? It might be worthwhile to extend beyond sequential recommendation tasks to broader scenarios. - The effectiveness of this method needs further validation in extremely large-scale datasets or user groups, or with more evaluation metrics. - It is hoped that the code will be made open-source for careful review. I may adjust my score based on this. - The reproducibility does not seem to be good enough, and no code link was found

Questions

see above

Rating

5

Confidence

3

Soundness

3

Presentation

3

Contribution

3

Limitations

see above

Authorsrebuttal2024-08-13

Dear Reviewer, Thank you very much for your valuable and positive feedback. We appreciate your recognition of our efforts in addressing your concerns, and we are encouraged by your comments that our responses have effectively addressed the issues raised. This motivates us to continue advancing the field with our research. Following your suggestion, we will incorporate the additional insights discussed in the rebuttal into the revised version of the paper. Thank you once again for your supportive and understanding comments. Best regards, Authors!

Reviewer 59LV2024-08-09

Thank you for taking the time to address my concerns. The rebuttal addressed most of them. I’ll raise my rating on "Soundness" and keep my overall rating.

Authorsrebuttal2024-08-14

Dear Reviewer, We would like to express our sincere gratitude for your valuable comments. Your insights on the **Fragile Setting of Sampled Evaluation** and **Limited Reference of MoE** have significantly helped us in establishing a more comprehensive and robust evaluation standard for the proposed iLoRA framework, as well as in providing a more thorough discussion of the relevant content. We hope that our responses have addressed most of your concerns. If so, we kindly ask if you could consider revising the overall rating of our paper. If there are any remaining concerns, we would be more than happy to further discuss them with you, especially since the rebuttal period is nearing its end. Please let us know if you have any additional questions. Thank you once again for your support and understanding! Best regards, Authors

Reviewer cnYP2024-08-13

To Authors

Thank you for your detailed rebuttal, which solved most of my concerns. I am willing to raise the rating to boarderline accept.

Program Chairsdecision2024-09-25

Decision

Accept (poster)

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