it is proposed to use the posterior mean instead of MAP ̄[4]
i.e.
to use square loss instead of 0-1 loss.The advantages are multiple:(1)much faster convergent speed.roughly 1/√ n versus 1/logn;(2)high precision in location of edges.especially for important corners
crossings and Y-shaped edges etc.;(3)more noise-resisting as indicated in[7].Both theoretical and experimental results are presented.