If I have 3 lists: points, faces and cells that represents a mesh, where:

• points is a list of x,y,z coordinates, for example

   [-0.05, -0.05,  0.  ],
   [-0.05,  0.05,  0.  ],
   [ 0.05, -0.05,  0.  ],
   ...
  

• faces is a list of list points, where each row is a list of point indices that represents a face

   [ 1,  4,  8,  7],
   [ 7,  8,  6,  3],
   [ 4,  0,  5,  8],
   ...
  

• cells is a list of list of points, where each row is a list of point indices that represents a cell

   [ 1,  7,  8,  4, 11, 16, 17, 10],
   [ 7,  3,  6,  8, 16, 15, 14, 17],
   [ 4,  8,  5,  0, 10, 17, 12,  9],
   ...
  

For each face, I need to get the two cells ids that are sharing the face (in case of boundary face, there is only one cell that owns that face).

For a small mesh, I can iterate over cells, and for each cell iterate over all faces and check if a face points are in current cell (two for loops and a face-cells map), which is of course awfully slow.

Is there a smarter way to efficiently get face connectivity of my mesh?

If I have 3 lists: points, faces and cells that represents a mesh, where:

• points is a list of x,y,z coordinates, for example

   [-0.05, -0.05,  0.  ],
   [-0.05,  0.05,  0.  ],
   [ 0.05, -0.05,  0.  ],
   ...
  

• faces is a list of list of points, where each row is a list of point indices that represents a face

   [ 1,  4,  8,  7],
   [ 7,  8,  6,  3],
   [ 4,  0,  5,  8],
   ...
  

• cells is a list of list of points, where each row is a list of point indices that represents a cell

   [ 1,  7,  8,  4, 11, 16, 17, 10],
   [ 7,  3,  6,  8, 16, 15, 14, 17],
   [ 4,  8,  5,  0, 10, 17, 12,  9],
   ...
  

For each face, I need to get the two cells ids that are sharing the face (in case of boundary face, there is only one cell that owns that face).

For a small mesh, I can iterate over cells, and for each cell iterate over all faces and check if a face points are in current cell (two for loops and a face-cells map), which is of course awfully slow.

Is there a smarter way to efficiently get face connectivity of my mesh?