Merge pull request #28 from ranjanan/relax

Relax B, add a test for symmetric sweep

Author: ranjanan

src/aggregation.jl

@@ -61,7 +61,8 @@ function extend_hierarchy!(levels, strength, aggregate, smooth,
     # b = zeros(eltype(A), size(A, 1))
 
     # Improve candidates
-    # relax!(improve_candidates, A, B, b)
+    b = zeros(size(A,1))
+    relax!(improve_candidates, A, B, b)
     T, B = fit_candidates(AggOp, B)
 
     P = smooth_prolongator(smooth, A, T, S, B)
@@ -86,7 +87,6 @@ function fit_candidates(AggOp, B, tol = 1e-10)
 
     R = zeros(eltype(B), n_coarse)
     Qx = zeros(eltype(B), nnz(A))
-   
     # copy!(Qx, B)
     for i = 1:size(Qx, 1)
         Qx[i] = B[i]
@@ -125,7 +125,11 @@ end
 function norm_col(A, Qx, i)
     s = zero(eltype(A))
     for j in nzrange(A, i)
-        val = Qx[A.rowval[j]]
+        if A.rowval[j] > length(Qx)
+            val = 1
+        else
+            val = Qx[A.rowval[j]]
+        end
         # val = A.nzval[A.rowval[j]]
         s += val*val
     end

src/smoother.jl

@@ -13,6 +13,7 @@ end
 GaussSeidel(iter = 1) = GaussSeidel(SymmetricSweep(), iter)
 GaussSeidel(f::ForwardSweep) = GaussSeidel(f, 1)
 GaussSeidel(b::BackwardSweep) = GaussSeidel(b, 1)
+GaussSeidel(s::SymmetricSweep) = GaussSeidel(s, 1)
 
 presmoother!(s, A, x, b) = smoother!(s, s.sweep, A, x, b)
 postsmoother!(s, A, x, b) = smoother!(s, s.sweep, A, x, b)
@@ -26,8 +27,8 @@ end
 
 function smoother!(s::GaussSeidel, ::SymmetricSweep, A, x, b)
     for i in 1:s.iter
-        smoother!(s, ForwardSweep(), A, x, b)
-        smoother!(s, BackwardSweep(), A, x, b)
+        gs!(A, b, x, 1, 1, size(A, 1))
+        gs!(A, b, x, size(A,1), -1, 1)
     end
 end
 

test/runtests.jl

@@ -268,4 +268,7 @@ end
 
 # Issue #24
 nodes_not_agg()
+
+# Issue 26
+test_symmetric_sweep()
 end

test/sa_tests.jl

@@ -320,3 +320,18 @@ function nodes_not_agg()
     @test size(ml.levels[2].A) == (11,11)
     @test size(ml.final_A) == (2,2)
 end
+
+# Issue 26
+import AMG: relax!
+function test_symmetric_sweep()
+    A = poisson(10)
+    s = GaussSeidel(SymmetricSweep(), 4)
+    x = ones(size(A,1))
+    b = zeros(size(A,1))
+    relax!(s, A, x, b)
+    @test sum(abs2, x - [0.176765; 0.353529; 0.497517; 0.598914; 
+                            0.653311; 0.659104; 0.615597; 0.52275; 
+                            0.382787; 0.203251]) < 1e-6
+        
+end
+