“…Consider the polygon interface problem with low regularity to illustrating the capability of OPWG. The example was considered in[19].Let the domain Ω = (0, 1) 2 with Ω 1 = [0.2, 0.8] × [0.3, 0.7] and Ω 2 = Ω/Ω 1 . The piecewise diffusive coefficients are taken as A 11 = 80, and A 22 = 1, and the exact solutions are chosen as follows: u(x, y) = (x 2 + y 2 ) 1.5 + sin(x + y), if (x, y) ∈ Ω 1 , v(x, y) = 1 + [(x − 0.5) 2 + (y − 0.5) 2 ] 0.5 , if (x, y) ∈ Ω 2 .…”