On Wed, Jan 26, 2011 at 3:18 PM, Hanno Klemm <klemm@phys.ethz.ch> wrote:
Mark,
interesting idea. Given the fact that in 2-d euclidean metric, the Einstein summation conventions are only a way to write out conventional matrix multiplications, do you consider at some point to include a non-euclidean metric in this thing? (As you have in special relativity, for example)
Something along the lines:
eta = np.diag(-1,1,1,1)
a = np.array(1,2,3,4) b = np.array(1,1,1,1)
such that
einsum('i,i', a,b, metric=eta) = -1 + 2 + 3 + 4
This particular example is already doable as follows:
eta = np.diag([-1,1,1,1]) eta array([[-1, 0, 0, 0], [ 0, 1, 0, 0], [ 0, 0, 1, 0], [ 0, 0, 0, 1]]) a = np.array([1,2,3,4]) b = np.array([1,1,1,1]) np.einsum('i,j,ij', a, b, eta) 8
I think that's right, did I understand you correctly? Cheers, Mark