[Nauty-list] vertex-invariants

Mr Fatih Demirkale fatih.demirkale at uqconnect.edu.au
Thu Aug 23 16:11:21 EST 2012


I have a few questions on the vertex-invariants. The questions might be too specific, and they might be already answered before, sorry about this.

I realized that the input minsize is not used in getbigcells function. Is line 439 in nautinv.c suppose to be "if (cell2 >= cell1 + minsize) "?

I wonder what is the motivation for using XOR ^ operator in celltrips (similarly in cellquads and cellquins). I know this is done to get "the number of vertices adjacent to an odd number of {v, v1, v2}". Is this done specifically for the bipartite graphs derived from block designs? As far I understand, it is wanted that the vertices are assigned with different codes as much as possible, and wt = FUZZ1(pc); gets different values if pc += POPCOUNT(sw); gets different values mod 4. Is this correct?

Lastly, could you please explain why the values in "fuzz1[] = {037541,061532,005257,026416};" are used?

Many thanks,


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