forum.polymake.org

Posted: **15 Jul 2016, 11:23**

Dear all,

there is a bug in computing the REGULAR property of a polyhedral fan. If I create the following fan, I get a negative result for REGULAR, however it is the normal fan of a polytope.

Best,
Sebastian

Code: Select all

fan > $rays=[[1,0,0,0],[0,1,0,0],[0,0,1,0],[1,0,-1,-1],[-1,-1,0,0]];

fan > $cones=[[1,2,3,5],[1,2,4,5],[1,3,4,5],[0,3,4,5],[0,1,3,4],[0,1,2,3],[0,2,3,5],[0,1,2,4],[0,2,4,5]];

fan > $fan=new PolyhedralFan( INPUT_RAYS=>$rays, INPUT_CONES=>$cones );

fan > print $fan->REGULAR;

fan > $p=new Polytope(INEQUALITIES=>[ [ 1,1,0,0,0 ], [ 1,0,1,0,0 ], [ 1,0,0,1,0 ], [ 1,0,0,0,1 ], [ 1,1,0,-1,-1 ], [ 1,-1,-1,0,0 ] ]);

fan > $fan2=normal_fan($p);

fan > print $fan2->MAXIMAL_CONES;
{1 2 3 5}
{1 2 4 5}
{1 3 4 5}
{0 3 4 5}
{0 1 3 4}
{0 1 2 3}
{0 2 3 5}
{0 1 2 4}
{0 2 4 5}

fan > print $fan2->RAYS;
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1
1 0 -1 -1
-1 -1 0 0

fan > print $fan2->REGULAR;
1

Posted: **15 Jul 2016, 17:09**

Hi,

thank you very much for the report. There was indeed a bug in our regularity client which we have now fixed in our development branch and the fix will also be included in 3.0r2 (which is scheduled for the next week).

Best,
Benjamin

PS: For anyone trying to reproduce this, the fourth unit vector is missing in the definition of $rays.

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Bug in REGULAR property of a polyhedral fan

Bug in REGULAR property of a polyhedral fan

Re: Bug in REGULAR property of a polyhedral fan