Add tests for LinearExponential() on GPU

lib/OrdinaryDiffEqLinear/src/linear_caches.jl

@@ -573,7 +573,7 @@ function _phiv_timestep_caches(u_prototype, maxiter::Int, p::Int)
     u = zero(u_prototype)                         # stores the current state
     W = Matrix{T}(undef, n, p + 1)                  # stores the w vectors
     P = Matrix{T}(undef, n, p + 2)                  # stores output from phiv!
-    Ks = KrylovSubspace{T}(n, maxiter)            # stores output from arnoldi!
+    Ks = KrylovSubspace{T,T,typeof(similar(u_prototype,size(u_prototype,1),2))}(n, maxiter) # stores output from arnoldi!
     phiv_cache = PhivCache(u_prototype, maxiter, p + 1) # cache used by phiv! (need +1 for error estimation)
     return u, W, P, Ks, phiv_cache
 end

test/gpu/linear_exp.jl

@@ -0,0 +1,35 @@
+using LinearAlgebra
+using SparseArrays
+using CUDA
+using CUDA.CUSPARSE
+using OrdinaryDiffEq
+
+# Linear exponential solvers
+A = MatrixOperator([2.0 -1.0; -1.0 2.0])
+u0 = ones(2)
+
+A_gpu =  MatrixOperator(cu([2.0 -1.0; -1.0 2.0]))
+u0_gpu = cu(ones(2))
+prob_gpu = ODEProblem(A_gpu, u0_gpu, (0.0, 1.0))
+
+sol_analytic = exp(1.0 * Matrix(A)) * u0
+
+sol1_gpu = solve(prob_gpu, LinearExponential(krylov = :off))(1.0) |> Vector
+sol2_gpu = solve(prob_gpu, LinearExponential(krylov = :simple))(1.0) |> Vector
+sol3_gpu = solve(prob_gpu, LinearExponential(krylov = :adaptive))(1.0) |> Vector
+
+@test isapprox(sol1_gpu, sol_analytic, rtol = 1e-6)
+@test isapprox(sol2_gpu, sol_analytic, rtol = 1e-6)
+@test isapprox(sol3_gpu, sol_analytic, rtol = 1e-6)
+
+A2_gpu =  MatrixOperator(cu(sparse([2.0 -1.0; -1.0 2.0])))
+prob2_gpu = ODEProblem(A2_gpu, u0_gpu, (0.0, 1.0))
+
+sol2_1_gpu = solve(prob2_gpu, LinearExponential(krylov = :off))(1.0) |> Vector
+sol2_2_gpu = solve(prob2_gpu, LinearExponential(krylov = :simple))(1.0) |> Vector
+sol2_3_gpu = solve(prob2_gpu, LinearExponential(krylov = :adaptive))(1.0) |> Vector
+
+@test isapprox(sol2_1_gpu, sol_analytic, rtol = 1e-6)
+@test isapprox(sol2_2_gpu, sol_analytic, rtol = 1e-6)
+@test isapprox(sol2_3_gpu, sol_analytic, rtol = 1e-6)
+@test isapprox(sol2_4_gpu, sol_analytic, rtol = 1e-4)

test/runtests.jl

@@ -172,6 +172,7 @@ end
         end
         @time @safetestset "Autoswitch GPU" include("gpu/autoswitch.jl")
         @time @safetestset "Linear LSRK GPU" include("gpu/linear_lsrk.jl")
+        @time @safetestset "Linear Exponential GPU" include("gpu/linear_exp.jl")
         @time @safetestset "Reaction-Diffusion Stiff Solver GPU" include("gpu/reaction_diffusion_stiff.jl")
         @time @safetestset "Scalar indexing bug bypass" include("gpu/hermite_test.jl")
     end