On Wed, Aug 30, 2006 at 12:08:26PM +0200, Chris Dams wrote:
This simple program
[...]
fails (both with GiNaC 1.4 CVS and 1.3.x). I believe that the reason is bug in indexed.cpp:reposition_dummy_indices() and propose attached patch to fix it. Note that patch *seems* to be correct, but IMHO it is somewhat ugly and probably inefficient. Could anyone suggest a better solution?
What if we simply don't do this kind of toggling of the variance in the case that both indices of the dummy pair belong to the same indexed object and the indexed object has a symmetry in which the dummy pair is involved? Then
T.mu.nu~mu~nu - T~nu~mu.nu.mu where T has cyclic symmetry, would not evaluate to zero. Which is (IMHO) very bad thing...
Seems simpler to me.
There exist a lot of simple *incorrect* solutions :) Best regards, Alexei -- All science is either physics or stamp collecting.