New functionality split_lincomb!

src/merge.jl

@@ -1,4 +1,5 @@
 export merge_graphs;
+export split_lincomb!;
 
 # Change a symbol name using prefix & postfix
 function translate_keyname(key, prefix, postfix, skip_basic, input)
@@ -115,3 +116,71 @@ function merge_graphs(
 
     return Compgraph{T}(operations, parents, coeffs, outputs)
 end
+
+
+"""
+      (g,cref_modified,new_crefs)=split_lincomb!(g,node,ind2;
+                        newnode=node_new,
+                        cref_list=[])
+
+Takes the lincomb operation in node and splits it into two lincombs, by
+creating a new node newnode. The new node consists of the linear combination
+of the coefficients moving (node, ind2[1]),... (node,ind2[end]) and the
+old lincomb object has the old coefficients and an additional term pointing
+to newnode. The cref_list is updated to the new coefficient pointers. The
+new_crefs list contains all the new coefficient pointers.
+
+
+In this way, the graph is unchanged but one of the linear combinations is
+split up into two.
+
+"""
+function split_lincomb!(g,node,ind2;
+                        newnode=Symbol("$(node)_new"),
+                        cref_list=[])
+
+    @show newnode
+    # get ind1 = complement of ind2
+    nof_lincombs=size(g.coeffs[node],1);
+    @show nof_lincombs
+    ind1=map(i -> !(i in ind2), 1:nof_lincombs)
+
+    org_parents=g.parents[node];
+    org_coeffs=g.coeffs[node];
+
+    @show org_coeffs
+
+    # Move ind2 to a new lincomb
+    add_lincomb!(g,newnode,org_coeffs[ind2],org_parents[ind2])
+
+    @show newnode
+    # Store ind1 lincomb info
+    new_parents1=[org_parents[ind1];newnode]
+    new_coeffs1=[org_coeffs[ind1];1]
+
+    # Update the node lincomb data to point ind2 + newnode
+    empty!(g.coeffs[node]);
+    push!(g.coeffs[node], new_coeffs1...)
+    empty!(g.parents[node]);
+    push!(g.parents[node], new_parents1...)
+
+
+    # Update the cref_list
+
+    new_crefs=[];
+    replace_list=Dict();
+    for (j,i)=enumerate(ind2);
+        replace_list[(node,i)]=(newnode,j)
+        push!(new_crefs,(newnode,j));
+    end
+
+
+    for (cref_old,cref_new) in replace_list
+        @show cref_old
+        @show cref_new
+        ii=findall( [cref_old] .== cref_list )
+        map(j -> cref_list[j]=cref_new, ii);
+    end
+
+    return (g,cref_list,new_crefs)
+end

test/merge_graphs.jl

@@ -37,3 +37,48 @@ using LinearAlgebra
     )
     @test eval_graph(graph_4, A) ≈ eval_graph(graph, eval_graph(graph, A))
 end
+@testset "split_lincomb" begin
+
+    A=[
+        0.196064  -1.18798    0.0        0.0         0.0         0.0       0.0
+        0.342678   0.793844   0.684638   0.0         0.0         0.0       0.0
+        1.26005    0.819614  -1.21473   -0.16794     0.0         0.0       0.0
+        -0.10478    1.50713    0.138891   0.652377   -0.580547    0.0       0.0
+        -0.803933  -1.96458    0.679152  -0.0471995  -0.0454885  -0.715895  0.0
+        -0.327724  -1.89847   -0.435685   1.44764    -0.928145    3.06844   1.19071];
+    B=[1.46284     0.594921   0.0         0.0        0.0        0.0        0.0
+       0.71404    -0.492136  -0.481715    0.0        0.0        0.0        0.0
+       0.237897   -0.946491   0.0070323   1.87826    0.0        0.0        0.0
+       0.0444275  -1.77078   -0.772886    0.89719    1.55139    0.0        0.0
+       -0.310057   -1.13217    1.40868     0.864775  -1.14717   -0.662986   0.0
+       -0.160165   -0.525442   0.676407   -0.934459   0.259851  -0.608684  -0.381333];
+    c=[-0.5210883864869685
+       -0.5011935108466905
+       0.9989082416364822
+       1.1643621428307982
+       -1.4603489516355923
+       2.405378746857791
+       1.7841340060684932
+       0.233340850959019];
+
+    degopt=Degopt(A,B,c);
+    n=size(A,1);
+    (g,cref)=graph_degopt(degopt);
+    g_org=deepcopy(g);
+    node=cref[50][1];;
+    ind2=[3;6];
+    (g,crefs,new_crefs)=split_lincomb!(g,node,ind2;
+                                       newnode=Symbol("$(node)_new"),
+                                       cref_list=[])
+
+    # Check that it is unmodified
+    @test  eval_graph(g,0.1) ≈ eval_graph(g_org,0.1)
+
+
+    # Check that changing a variable has the same effect
+    set_coeffs!(g_org,[3.3],[(node,ind2[1])])
+    set_coeffs!(g,[3.3],[new_crefs[1]])
+
+    @test eval_graph(g,0.3) ≈ eval_graph(g_org,0.3)
+
+end