 Creative Commons Attribution 3.0 Unported license
                
    Creative Commons Attribution 3.0 Unported license
 
    A long line of research on fixed parameter tractability of integer programming culminated with showing that integer programs with n variables and a constraint matrix with tree-depth d and largest entry Δ are solvable in time g(d,Δ) poly(n) for some function g, i.e., fixed parameter tractable when parameterized by tree-depth d and Δ. However, the tree-depth of a constraint matrix depends on the positions of its non-zero entries and thus does not reflect its geometric structure. In particular, tree-depth of a constraint matrix is not preserved by row operations, i.e., a given integer program can be equivalent to another with a smaller dual tree-depth. We prove that the branch-depth of the matroid defined by the columns of the constraint matrix is equal to the minimum tree-depth of a row-equivalent matrix. We also design a fixed parameter algorithm parameterized by an integer d and the entry complexity of an input matrix that either outputs a matrix with the smallest dual tree-depth that is row-equivalent to the input matrix or outputs that there is no matrix with dual tree-depth at most d that is row-equivalent to the input matrix. Finally, we use these results to obtain a fixed parameter algorithm for integer programming parameterized by the branch-depth of the input constraint matrix and the entry complexity. The parameterization by branch-depth cannot be replaced by the more permissive notion of branch-width.
@InProceedings{chan_et_al:LIPIcs.ICALP.2020.26,
  author =	{Chan, Timothy F. N. and Cooper, Jacob W. and Kouteck\'{y}, Martin and Kr\'{a}l', Daniel and Pek\'{a}rkov\'{a}, Krist\'{y}na},
  title =	{{Matrices of Optimal Tree-Depth and Row-Invariant Parameterized Algorithm for Integer Programming}},
  booktitle =	{47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)},
  pages =	{26:1--26:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-138-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{168},
  editor =	{Czumaj, Artur and Dawar, Anuj and Merelli, Emanuela},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2020.26},
  URN =		{urn:nbn:de:0030-drops-124339},
  doi =		{10.4230/LIPIcs.ICALP.2020.26},
  annote =	{Keywords: Matroid algorithms, width parameters, integer programming, fixed parameter tractability, branch-width, branch-depth}
}
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                     
                                                                                                            
                    