publications

2026

1. Preprint

   AGORA: Reliability-Aware Aggregation of LLM Judges via Item-Response Theory

   Junhyung Ahn

   2026

   Preprint

   Bib

   @unpublished{ahn2026agora,
     title = {{AGORA}: Reliability-Aware Aggregation of {LLM} Judges via Item-Response Theory},
     author = {Ahn, Junhyung},
     year = {2026},
     note = {Preprint}
   }

2025

1. ICDM

   On Predicting Post-Click Conversion Rate via Counterfactual Inference

   Junhyung Ahn and Sanghack Lee

   In IEEE International Conference on Data Mining (ICDM), 2025

   Best Paper Finalist Abs DOI arXiv Bib HTML

   Best Paper Award Finalist, IEEE ICDM 2025

   Conversion rate prediction suffers from selection bias: conversion labels are observed only for clicked impressions. We cast the missing labels as a counterfactual quantity and impute conversions for non-clicked samples via counterfactual inference, improving both offline estimation and online conversion rate.

   @inproceedings{ahn2025postclick,
     title = {On Predicting Post-Click Conversion Rate via Counterfactual Inference},
     author = {Ahn, Junhyung and Lee, Sanghack},
     booktitle = {IEEE International Conference on Data Mining (ICDM)},
     pages = {11--20},
     year = {2025},
     doi = {10.1109/ICDM65498.2025.00008},
   }

2024

1. IEEE TIT

   On the Fundamental Limits of Matrix Completion: Leveraging Hierarchical Similarity Graphs

   Junhyung Ahn, Adel Elmahdy, Soheil Mohajer, and 1 more author

   IEEE Transactions on Information Theory, 2024

   DOI arXiv Bib HTML

   @article{ahn2024fundamental,
     title = {On the Fundamental Limits of Matrix Completion: Leveraging Hierarchical Similarity Graphs},
     author = {Ahn, Junhyung and Elmahdy, Adel and Mohajer, Soheil and Suh, Changho},
     journal = {IEEE Transactions on Information Theory},
     volume = {70},
     number = {3},
     pages = {2039--2075},
     year = {2024},
     doi = {10.1109/TIT.2023.3345902},
   }

2022

1. ISIT

   The Optimal Sample Complexity of Matrix Completion with Hierarchical Similarity Graphs

   Adel Elmahdy, Junhyung Ahn, Soheil Mohajer, and 1 more author

   In IEEE International Symposium on Information Theory (ISIT), 2022

   DOI Bib HTML

   @inproceedings{elmahdy2022optimal,
     title = {The Optimal Sample Complexity of Matrix Completion with Hierarchical Similarity Graphs},
     author = {Elmahdy, Adel and Ahn, Junhyung and Mohajer, Soheil and Suh, Changho},
     booktitle = {IEEE International Symposium on Information Theory (ISIT)},
     pages = {2409--2414},
     year = {2022},
     doi = {10.1109/ISIT50566.2022.9834449},
   }

2020

1. NeurIPS

   Matrix Completion with Hierarchical Graph Side Information

   Adel Elmahdy^*, Junhyung Ahn^*, Changho Suh, and 1 more author

   In Advances in Neural Information Processing Systems (NeurIPS), 2020

   Equal contribution.

   Abs arXiv Bib HTML PDF

   We consider a matrix completion problem that exploits social or item similarity graphs as side information, characterize the information-theoretic limit on the number of observed entries needed for exact recovery, and give a computationally efficient algorithm that achieves it.

   @inproceedings{elmahdy2020matrix,
     title = {Matrix Completion with Hierarchical Graph Side Information},
     author = {Elmahdy, Adel and Ahn, Junhyung and Suh, Changho and Mohajer, Soheil},
     booktitle = {Advances in Neural Information Processing Systems (NeurIPS)},
     volume = {33},
     pages = {9061--9074},
     year = {2020},
     note = {Equal contribution.}
   }