Attempting the Impossible: Enumerating Extremal Submodular Functions for n = 6
Enumerating the extremal submodular functions defined on subsets of a fixed base set has only been done for base sets up to five elements. This paper reports the results of attempting to generate all such functions on a six-element base set. Using improved tools from polyhedral geometry, we have com...
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MDPI AG
2024-12-01
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| Series: | Mathematics |
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| author | Elod P. Csirmaz Laszlo Csirmaz |
| author_facet | Elod P. Csirmaz Laszlo Csirmaz |
| author_sort | Elod P. Csirmaz |
| collection | DOAJ |
| description | Enumerating the extremal submodular functions defined on subsets of a fixed base set has only been done for base sets up to five elements. This paper reports the results of attempting to generate all such functions on a six-element base set. Using improved tools from polyhedral geometry, we have computed 360 billion of them, and provide the first reasonable estimate of their total number, which is expected to be between 1000 and 10,000 times this number. The applied Double Description and Adjacency Decomposition methods require an insertion order of the defining inequalities. We introduce two novel orders, which speed up the computations significantly, and provide additional insight into the highly symmetric structure of submodular functions. We also present an improvement to the combinatorial test used as part of the Double Description method, and use statistical analyses to estimate the degeneracy of the polyhedral cone used to describe these functions. The statistical results also highlight the limitations of the applied methods. |
| format | Article |
| id | doaj-art-27854dc8ca104ac2a8644a630443c649 |
| institution | Kabale University |
| issn | 2227-7390 |
| language | English |
| publishDate | 2024-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Mathematics |
| spelling | doaj-art-27854dc8ca104ac2a8644a630443c6492025-01-10T13:18:15ZengMDPI AGMathematics2227-73902024-12-011319710.3390/math13010097Attempting the Impossible: Enumerating Extremal Submodular Functions for n = 6Elod P. Csirmaz0Laszlo Csirmaz1Alfréd Rényi Institute of Mathematics, 1053 Budapest, HungaryAlfréd Rényi Institute of Mathematics, 1053 Budapest, HungaryEnumerating the extremal submodular functions defined on subsets of a fixed base set has only been done for base sets up to five elements. This paper reports the results of attempting to generate all such functions on a six-element base set. Using improved tools from polyhedral geometry, we have computed 360 billion of them, and provide the first reasonable estimate of their total number, which is expected to be between 1000 and 10,000 times this number. The applied Double Description and Adjacency Decomposition methods require an insertion order of the defining inequalities. We introduce two novel orders, which speed up the computations significantly, and provide additional insight into the highly symmetric structure of submodular functions. We also present an improvement to the combinatorial test used as part of the Double Description method, and use statistical analyses to estimate the degeneracy of the polyhedral cone used to describe these functions. The statistical results also highlight the limitations of the applied methods.https://www.mdpi.com/2227-7390/13/1/97vertex enumerationdouble description methodsubmodular functions |
| spellingShingle | Elod P. Csirmaz Laszlo Csirmaz Attempting the Impossible: Enumerating Extremal Submodular Functions for n = 6 Mathematics vertex enumeration double description method submodular functions |
| title | Attempting the Impossible: Enumerating Extremal Submodular Functions for n = 6 |
| title_full | Attempting the Impossible: Enumerating Extremal Submodular Functions for n = 6 |
| title_fullStr | Attempting the Impossible: Enumerating Extremal Submodular Functions for n = 6 |
| title_full_unstemmed | Attempting the Impossible: Enumerating Extremal Submodular Functions for n = 6 |
| title_short | Attempting the Impossible: Enumerating Extremal Submodular Functions for n = 6 |
| title_sort | attempting the impossible enumerating extremal submodular functions for n 6 |
| topic | vertex enumeration double description method submodular functions |
| url | https://www.mdpi.com/2227-7390/13/1/97 |
| work_keys_str_mv | AT elodpcsirmaz attemptingtheimpossibleenumeratingextremalsubmodularfunctionsforn6 AT laszlocsirmaz attemptingtheimpossibleenumeratingextremalsubmodularfunctionsforn6 |