Peer-reviewedCC BYForum Math. Sigma
An algorithm for uniform generation of unlabeled (Pólya) trees
Abstract
Pólya trees are unlabeled rooted trees on n vertices. This paper gives a new way to generate Pólya trees, that conjecturally is very efficient. This allows comparing typical unlabeled and labeled tree statistics and comparing asymptotic theorems with “reality.” Our method is an application of the Burnside process, alternating two steps: from a labeled rooted tree, produce a uniform permutation fixing it; and from a permutation, produce a uniform labeled rooted tree fixed by it. This last step is linked to a product formula, refining Cayley’s, for the number of rooted labeled trees preserved by a given permutation.
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BibTeX
@article{bartholdi2026algorithm,
title = {{An algorithm for uniform generation of unlabeled (Pólya) trees}},
author = {Laurent Bartholdi and Persi Diaconis},
journal = {Forum Math. Sigma},
year = {2026},
month = nov,
doi = {10.1017/fms.2026.10218},
url = {https://hal.science/hal-05849739v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - An algorithm for uniform generation of unlabeled (Pólya) trees
AU - Laurent Bartholdi
AU - Persi Diaconis
PY - 2026
DA - 2026/11/03
JO - Forum Math. Sigma
DO - 10.1017/fms.2026.10218
UR - https://hal.science/hal-05849739v1
AB - Pólya trees are unlabeled rooted trees on n vertices. This paper gives a new way to generate Pólya trees, that conjecturally is very efficient. This allows comparing typical unlabeled and labeled tree statistics and comparing asymptotic theorems with “reality.” Our method is an application of the Burnside process, alternating two steps: from a labeled rooted tree, produce a uniform permutation fixing it; and from a permutation, produce a uniform labeled rooted tree fixed by it. This last step is linked to a product formula, refining Cayley’s, for the number of rooted labeled trees preserved by a given permutation.
ER -