optimize renomarlize_south_edge

Author: ogauthe

src/algorithms/contractions/ctmrg_contractions.jl

@@ -1024,6 +1024,16 @@ function renormalize_south_edge(E_south, P_left, P_right, A)
     return renormalize_west_edge(E_south, P_left, P_right, A_west)
 end
 
+function renormalize_south_edge(E_south::CTMRG_PF_EdgeTensor, P_left, P_right, A::PFTensor)
+    # specialize to avoid extra permute on A when calling renormalize_west_edge
+    return @tensor begin
+        temp[χ_W D_W; χSW] := P_left[χSW D_W; χ_W]  # impose χ_W as 1st leg
+        PE[χ_W χSE; D_W D_S] := temp[χ_W D_W; χSW] * E_south[χSE D_S; χSW]
+        PEA[χ_W D_N; χSE D_E] := PE[χ_W χSE; D_W D_S] * A[D_W D_S; D_N D_E]
+        edge[χ_E D_N; χ_W] := PEA[χ_W D_N; χSE D_E] * P_right[χ_E; χSE D_E]
+    end
+end
+
 """
     renormalize_west_edge((row, col), env, P_top, P_bottom, network::InfiniteSquareNetwork{P})
     renormalize_west_edge(E_west, P_top, P_bottom, A::P)