_isidentity_struct

Author: vpuri3

src/LinearSolve.jl

@@ -42,6 +42,14 @@ needs_concrete_A(alg::AbstractFactorization) = true
 needs_concrete_A(alg::AbstractKrylovSubspaceMethod) = false
 needs_concrete_A(alg::AbstractSolveFunction) = false
 
+# Util
+_isidentity_struct(A) = false
+_isidentity_struct(λ::Number) = isone(λ)
+_isidentity_struct(A::UniformScaling) = isone(A.λ)
+_isidentity_struct(::IterativeSolvers.Identity) = true
+_isidentity_struct(::SciMLBase.IdentityOperator) = true
+_isidentity_struct(::SciMLBase.DiffEqIdentity) = true
+
 # Code
 
 const INCLUDE_SPARSE = Preferences.@load_preference("include_sparse", Base.USE_GPL_LIBS)

src/iterative_wrappers.jl

@@ -150,8 +150,9 @@ function SciMLBase.solve(cache::LinearCache, alg::KrylovJL; kwargs...)
     M = cache.Pl
     N = cache.Pr
 
-    M = (M === Identity()) ? I : InvPreconditioner(M)
-    N = (N === Identity()) ? I : InvPreconditioner(N)
+    # use no-op preconditioner for Krylov.jl (LinearAlgebra.I) when M/N is identity
+    M = _isidentity_struct(M) ? I : InvPreconditioner(M)
+    N = _isidentity_struct(M) ? I : InvPreconditioner(N)
 
     atol = float(cache.abstol)
     rtol = float(cache.reltol)
@@ -234,15 +235,15 @@ function init_cacheval(alg::IterativeSolversJL, A, b, u, Pl, Pr, maxiters::Int,
               alg.kwargs...)
 
     iterable = if alg.generate_iterator === IterativeSolvers.cg_iterator!
-        Pr !== Identity() &&
+        ! _isidentity_struct(Pr) &&
             @warn "$(alg.generate_iterator) doesn't support right preconditioning"
         alg.generate_iterator(u, A, b, Pl;
                               kwargs...)
     elseif alg.generate_iterator === IterativeSolvers.gmres_iterable!
         alg.generate_iterator(u, A, b; Pl = Pl, Pr = Pr, restart = restart,
                               kwargs...)
     elseif alg.generate_iterator === IterativeSolvers.bicgstabl_iterator!
-        Pr !== Identity() &&
+        ! _isidentity_struct(Pr) &&
             @warn "$(alg.generate_iterator) doesn't support right preconditioning"
         alg.generate_iterator(u, A, b, alg.args...; Pl = Pl,
                               abstol = abstol, reltol = reltol,

test/runtests.jl

@@ -26,6 +26,7 @@ if GROUP == "All" || GROUP == "Core"
     @time @safetestset "Non-Square Tests" begin include("nonsquare.jl") end
     @time @safetestset "SparseVector b Tests" begin include("sparse_vector.jl") end
     @time @safetestset "Default Alg Tests" begin include("default_algs.jl") end
+    @time @safetestset "Traits" begin include("traits.jl") end
 end
 
 if GROUP == "LinearSolveCUDA"

test/traits.jl

@@ -0,0 +1,16 @@
+#
+using LinearSolve, LinearAlgebra, Test
+using LinearSolve: _isidentity_struct
+
+N = 4
+
+@testset "Traits" begin
+
+    @test _isidentity_struct(I)
+    @test _isidentity_struct(1.0 * I)
+    @test _isidentity_struct(SciMLBase.IdentityOperator{N}())
+    @test _isidentity_struct(SciMLBase.DiffEqIdentity(rand(4)))
+    @test ! _isidentity_struct(2.0 * I)
+    @test ! _isidentity_struct(rand(N, N))
+    @test ! _isidentity_struct(Matrix(I, N, N))
+end