[Nauty-list] Permanent canonical form...

[Brendan McKay]

The word size (16, 32 or 64) is guaranteed to not change the
canonical form.  This has been true since version 2.0.
Same with big-endian versus little-endian hardware.
In general, the compiler you use and the hardware you run
it on should have no effect on the canonical form.

The values of some user-settable parameters certainly DO change
the canonical form and preventing that is impossible in principle
since those parameters are intended to change the computation in
fundamental ways.  The compile-time parameters MAXN and WORDSIZE
do not change the canonical form, however.

The canonical form has not changed over a few years worth of
nauty versions, but I can't promise that will always be true
without eliminating future efficiency enhancements.

Brendan.


* Gordon Royle <GORDON at CSSE.UWA.EDU.AU> [070529 14:42]:
> As far as I understand, the canonical forms produced by nauty are not  
> "guaranteed" in that they can vary with
> 
> - a change in nauty version
> - a change of machine architecture (?? does using 32-bit versus 64- 
> bit Linux alter things?)
> - (user controllable) changes to nauty parameters
> 
> Is there any way of specifying a permanent machine independent  
> canonical form via nauty, even at the possible expense of speed...
> 
> Cheers
> 
> Gordon
> 
> --
> Associate Professor Gordon Royle
> Department of Computer Science & Software Engineering
> University of Western Australia
> http://people.csse.uwa.edu.au/gordon
> 
> 
> 
> 
> 
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