Implement create global stiffness and mass matrices

src/ModelReduction.jl

@@ -3,4 +3,7 @@
 
 module ModelReduction
 
+include("global_stiffness.jl")
+include("global_mass.jl")
+
 end

src/global_mass.jl

@@ -0,0 +1,10 @@
+# This file is a part of JuliaFEM.
+# License is MIT: see https://github.com/JuliaFEM/ModelReduction.jl/blob/master/LICENSE
+
+function global_mass(m, N)
+    M = zeros(N,N)
+    for i=1:N-1
+      M[i:i+1,i:i+1] += m
+    end
+    return M
+end

src/global_stiffness.jl

@@ -0,0 +1,10 @@
+# This file is a part of JuliaFEM.
+# License is MIT: see https://github.com/JuliaFEM/ModelReduction.jl/blob/master/LICENSE
+
+function global_stiffness(k, N)
+    K = zeros(N,N)
+    for i=1:N-1
+      K[i:i+1,i:i+1] += k
+    end
+    return K
+end

test/runtests.jl

@@ -5,4 +5,6 @@ using ModelReduction
 using Base.Test
 
 @testset "ModelReduction.jl" begin
+    include("test_global_stiffness.jl")
+    include("test_global_mass.jl")
 end

test/test_global_mass.jl

@@ -0,0 +1,19 @@
+# This file is a part of JuliaFEM.
+# License is MIT: see https://github.com/JuliaFEM/ModelReduction.jl/blob/master/LICENSE
+
+using ModelReduction
+
+m = [1 0; 0 1]
+
+N = 5
+
+@testset "Build the global mass matrix" begin
+    expected =
+    [1.0 0.0 0.0 0.0 0.0;
+     0.0 2.0 0.0 0.0 0.0;
+     0.0 0.0 2.0 0.0 0.0;
+     0.0 0.0 0.0 2.0 0.0;
+     0.0 0.0 0.0 0.0 1.0]
+    result = ModelReduction.global_mass(m, N)
+    @test result ≈ expected
+end

test/test_global_stiffness.jl

@@ -0,0 +1,19 @@
+# This file is a part of JuliaFEM.
+# License is MIT: see https://github.com/JuliaFEM/ModelReduction.jl/blob/master/LICENSE
+
+using ModelReduction
+
+k = [1 -1; -1 1]
+
+N = 5
+
+@testset "Build the global stiffness matrix" begin
+    expected =
+    [1.0 -1.0 0.0 0.0 0.0;
+    -1.0 2.0 -1.0 0.0 0.0;
+    0.0 -1.0 2.0 -1.0 0.0;
+    0.0 0.0 -1.0 2.0 -1.0;
+    0.0 0.0 0.0 -1.0 1.0]
+    result = ModelReduction.global_stiffness(k, N)
+    @test result ≈ expected
+end