Write simpler Gauss Seidel smoother

Author: ranjanan

src/multilevel.jl

@@ -16,8 +16,8 @@ abstract type CoarseSolver end
 struct Pinv <: CoarseSolver
 end
 
-MultiLevel{Ti,Tv}(l::Vector{Level{Ti,Tv}}, A::SparseMatrixCSC{Ti,Tv}, presmoother, postsmoother; coarse_solver = Pinv()) =
-    MultiLevel(l, A, coarse_solver, presmoother, postsmoother)
+MultiLevel{Ti,Tv}(l::Vector{Level{Ti,Tv}}, A::SparseMatrixCSC{Ti,Tv}, presmoother, postsmoother) =
+    MultiLevel(l, A, Pinv(), presmoother, postsmoother)
 Base.length(ml) = length(ml.levels) + 1
 
 function Base.show(io::IO, ml::MultiLevel)

src/preconditioner.jl

@@ -6,8 +6,8 @@ end
 
 aspreconditioner(ml::MultiLevel) = Preconditioner(ml)
 
-\(p::Preconditioner, b) = p * b
-*(p::Preconditioner, b) = solve(p.ml, b, 1, V(), 1e-12)
+\(p::Preconditioner, b) = solve(p.ml, b, 1, V(), 1e-12)
+*(p::Preconditioner, b) = p.ml.levels[1].A * x
 
 A_ldiv_B!(x, p::Preconditioner, b) = copy!(x, p \ b)
 A_mul_B!(b, p::Preconditioner, x) = A_mul_B!(b, p.ml.levels[1].A, x)

src/smoother.jl

@@ -7,10 +7,33 @@ end
 struct GaussSeidel{S} <: Smoother
     sweep::S
 end
-GaussSeidel(;sweep = ForwardSweep()) = GaussSeidel(sweep)
+GaussSeidel() = GaussSeidel(ForwardSweep())
 
 presmoother!(s, A, x, b) = smoother(s, s.sweep, A, x, b)
 postsmoother!(s, A, x, b) = smoother(s, s.sweep, A, x, b)
 
 smoother(s::GaussSeidel, ::ForwardSweep, A, x, b) =
-                        gauss_seidel!(x, A, b, maxiter = 1)
+                    gs!(A, b, x)
+                        #gauss_seidel!(x, A, b, maxiter = 1)
+
+function gs!{T,Ti}(A::SparseMatrixCSC{T,Ti}, b::Vector{T}, x::Vector{T})
+    n = size(A, 1)
+    z = zero(eltype(A))
+    for i = 1:n
+        # rsum = calc_weighted_sum(A, x)
+        rsum = z
+        diag = z
+        for j in nzrange(A, i)
+            row = A.rowval[j]
+            val = A.nzval[j]
+            if i == row
+                diag = val
+            else
+                rsum += val * x[row]
+            end
+        end
+        if diag != 0
+            x[i] = (b[i] - rsum) / diag
+        end
+    end
+end