Merge pull request #145 from sjdaines/matrix_colors_storedzeros

matrix_colors include sparse matrix stored zeros (structural nonzeros)

Author: ChrisRackauckas

src/coloring/high_level.jl

@@ -12,6 +12,9 @@ struct AcyclicColoring <: SparseDiffToolsColoringAlgorithm end
 Return the colorvec vector for the matrix A using the chosen coloring
 algorithm. If a known analytical solution exists, that is used instead.
 The coloring defaults to a greedy distance-1 coloring.
+
+Note that if A isa SparseMatrixCSC, the sparsity pattern is defined by structural nonzeroes,
+ie includes explicitly stored zeros.
 """
 function ArrayInterface.matrix_colors(A::AbstractMatrix, alg::SparseDiffToolsColoringAlgorithm = GreedyD1Color(); partition_by_rows::Bool = false)
     _A = A isa SparseMatrixCSC ? A : sparse(A) # Avoid the copy

src/coloring/matrix2graph.jl

@@ -32,10 +32,12 @@ A utility function to generate a graph from input
 sparse matrix, columns are represented with vertices
 and 2 vertices are connected with an edge only if
 the two columns are mutually orthogonal.
+
+Note that the sparsity pattern is defined by structural nonzeroes, ie includes
+explicitly stored zeros.
 """
 function matrix2graph(sparse_matrix::SparseMatrixCSC{<:Number, Int}, partition_by_rows::Bool=true)
-
-    dropzeros!(sparse_matrix)
+    
     (rows_index, cols_index, _) = findnz(sparse_matrix)
 
     ncols = size(sparse_matrix, 2)

test/test_matrix2graph.jl

@@ -40,3 +40,22 @@ for i in 1:20
         @test pr != 0
     end
 end
+
+@info "stored zeros"
+for i in 1:20  
+    matrix = matrices[i]
+    g = matrix2graph(matrix)
+    # recalculate graph with stored zeros
+    matrix_sz = copy(matrix)
+    fill!(matrix_sz, 0.0)
+    g_sz = matrix2graph(matrix_sz)
+    # check that graphs are the same 
+    @test nv(g) == nv(g_sz)
+    @test ne(g) == ne(g_sz)
+    for e in edges(g)
+        @test has_edge(g_sz, e)
+    end
+    for e in edges(g_sz)
+        @test has_edge(g, e)
+    end    
+end