Foto Hans-Peter Lehmann

M.Sc. Hans-Peter Lehmann

Research Interests

I'm working on compact data structures, in particular different variants of perfect hashing. A perfect hash function is a function h: S → [m] which has no collisions on a given input set S. Among others, I have focused on the following variants:

  • Non-minimal perfect hash functions (|S| > m) with SicHash.
  • Parallel minimal perfect hash functions (|S| = m) with GPURecSplit/SIMDRecSplit
  • Perfect hashing for objects of variable size with PaCHash
  • Monotone minimal perfect hash functions (output is lexicographically sorted) with LeMonHash

Furthermore, I am interested in index data structures in general, as well as accelerating algorithms using GPUs.

Software
Bild Title Short Description Source Code Corresponding Paper

A Perfect Hash Function based on irregular cuckoo hashing

ByteHamster/SicHash

ALENEX 2023

External perfect hash table for objects of variable size

ByteHamster/PaCHash

ALENEX 2023

Parallelization of a space-efficient minimal perfect hash function

ByteHamster/GpuRecSplit

arXiv

Monotone Minimal Perfect Hashing based on Retrieval and the PGM-Index

ByteHamster/LeMonHash

arXiv

Space-efficient perfect hash function based on finding random pseudoforests

ByteHamster/ShockHash

arXiv

Publications


ShockHash: Towards Optimal-Space Minimal Perfect Hashing Beyond Brute-Force
Lehmann, H.-P.; Sanders, P.; Walzer, S.
2024. Proceedings : 2024 Proceedings of the Symposium on Algorithm Engineering and Experiments (ALENEX). Ed.: R. Chowdhury, 194–206, Society for Industrial and Applied Mathematics (SIAM). doi:10.1137/1.9781611977929.15
Learned Monotone Minimal Perfect Hashing
Ferragina, P.; Lehmann, H.-P.; Sanders, P.; Vinciguerra, G.
2023. 31st Annual European Symposium on Algorithms (ESA 2023), Schloss Dagstuhl - Leibniz-Zentrum für Informatik. Ed.: I. Gørtz, 46:1–46:17, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (LZI). doi:10.4230/LIPIcs.ESA.2023.46
High Performance Construction of RecSplit Based Minimal Perfect Hash Functions
Bez, D.; Kurpicz, F.; Lehmann, H.-P.; Sanders, P.
2023. 31st Annual European Symposium on Algorithms (ESA 2023), Schloss Dagstuhl - Leibniz-Zentrum für Informatik. Ed.: I. Gørtz, 19:1–19:16, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (LZI). doi:10.4230/LIPIcs.ESA.2023.19
PaCHash: Packed and Compressed Hash Tables
Kurpicz, F.; Lehmann, H.-P.; Sanders, P.
2023. 2023 Proceedings of the Symposium on Algorithm Engineering and Experiments (ALENEX), 162–175, Society for Industrial and Applied Mathematics (SIAM). doi:10.1137/1.9781611977561.ch14
SicHash - Small Irregular Cuckoo Tables for Perfect Hashing
Lehmann, H.-P.; Sanders, P.; Walzer, S.
2023. 2023 Proceedings of the Symposium on Algorithm Engineering and Experiments (ALENEX), Florence, I, January 22-23,2023, 176–189, Society for Industrial and Applied Mathematics (SIAM). doi:10.1137/1.9781611977561.ch15
Weighted Random Sampling - Alias Tables on the GPU. master’s thesis
Lehmann, H.-P.
2021. Karlsruher Institut für Technologie (KIT). doi:10.5445/IR/1000133378
Technical Reports
Title Authors Source Date

Hans-Peter Lehmann, Peter Sanders, Stefan Walzer

arXiv:2310.14959

October 2023

Hans-Peter Lehmann, Peter Sanders, Stefan Walzer

arXiv:2308.09561

August 2023

Paolo Ferragina, Hans-Peter Lehmann, Peter Sanders, Giorgio Vinciguerra

arXiv:2304.11012

April 2023

Dominik Bez, Florian Kurpicz, Hans-Peter Lehmann, Peter Sanders

arXiv:2212.09562

December 2022

Hans-Peter Lehmann, Peter Sanders, Stefan Walzer

arXiv:2210.01560

October 2022

Florian Kurpicz, Hans-Peter Lehmann, Peter Sanders

arXiv:2205.04745

May 2022

Hans-Peter Lehmann, Lorenz Hübschle-Schneider, and Peter Sanders

arXiv:2106.12270

June 2021
Präsentationen
Title Conference Author(s) Speaker

Symposium on Algorithm Engineering and Experiments (ALENEX'24)

Hans-Peter Lehmann, Peter Sanders, Stefan Walzer

Hans-Peter Lehmann

European Symposium on Algorithms (ESA'23)

Dominik Bez, Florian Kurpicz, Hans-Peter Lehmann, Peter Sanders

Hans-Peter Lehmann

Symposium on Algorithm Engineering and Experiments (ALENEX'23)

Hans-Peter Lehmann, Peter Sanders, Stefan Walzer

Hans-Peter Lehmann

Teaching

Lectures
Title Type Semester
Vorlesung / Übung (VÜ) WS 23/24
Praxis der Softwareentwicklung WS 23/24
Seminar (S) SS 2023
Vorlesung (V) WS 22/23
Praxis der Softwareentwicklung WS 22/23
Praxis der Softwareentwicklung SS 2022
Vorlesung (V) WS 21/22
Vorlesung (V) SS 2021
Active Theses