--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/+sbp/+implementations/intOpAWW_orders_4to4_ratio2to1.m	Sat Oct 14 22:32:25 2017 -0700
@@ -0,0 +1,47 @@
+function [IC2F,IF2C,Hc,Hf] = IntOp_orders_4to4_ratio2to1(mc,hc,ACC)
+
+% ACC is a string.
+% ACC = 'C2F' creates IC2F with one order of accuracy higher than IF2C.
+% ACC = 'F2C' creates IF2C with one order of accuracy higher than IC2F.
+ratio = 2;
+mf = ratio*mc-1; 
+hf = hc/ratio;
+
+switch ACC
+    case 'F2C'
+        [stencil_F2C,BC_F2C,HcU,HfU] = ...
+        sbp.implementations.intOpAWW_orders_4to4_ratio_2to1_accC2F2_accF2C3;
+    case 'C2F'
+        [stencil_F2C,BC_F2C,HcU,HfU] = ...
+        sbp.implementations.intOpAWW_orders_4to4_ratio_2to1_accC2F3_accF2C2;
+end
+
+stencil_width = length(stencil_F2C);
+stencil_hw = (stencil_width-1)/2;
+[BC_rows,BC_cols] = size(BC_F2C);
+
+%%% Norm matrices %%%
+Hc = speye(mc,mc);
+HcUm = length(HcU); 
+Hc(1:HcUm,1:HcUm) = spdiags(HcU',0,HcUm,HcUm);
+Hc(mc-HcUm+1:mc,mc-HcUm+1:mc) = spdiags(rot90(HcU',2),0,HcUm,HcUm);
+Hc = Hc*hc;
+
+Hf = speye(mf,mf);
+HfUm = length(HfU);
+Hf(1:HfUm,1:HfUm) = spdiags(HfU',0,HfUm,HfUm);
+Hf(mf-length(HfU)+1:mf,mf-length(HfU)+1:mf) = spdiags(rot90(HfU',2),0,HfUm,HfUm);
+Hf = Hf*hf;
+%%%%%%%%%%%%%%%%%%%%%%
+
+%%% Create IF2C from stencil and BC
+IF2C = sparse(mc,mf);
+for i = BC_rows+1 : mc-BC_rows
+    IF2C(i,ratio*i-1+(-stencil_hw:stencil_hw)) = stencil_F2C; %#ok<SPRIX>
+end
+IF2C(1:BC_rows,1:BC_cols) = BC_F2C;
+IF2C(end-BC_rows+1:end,end-BC_cols+1:end) = rot90(BC_F2C,2);
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%% Create IC2F using symmetry condition %%%%
+IC2F = Hf\IF2C.'*Hc;
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