From 8ddea4c94c65deff451b8e5b7b3e956025ebd563 Mon Sep 17 00:00:00 2001
From: Fredrik Ekre <ekrefredrik@gmail.com>
Date: Wed, 27 Jul 2022 16:26:23 +0200
Subject: [PATCH] Automatically apply required default settings when using
 solvers as preconditioner.

---
 gen/solver_options.jl | 1 +
 src/Internals.jl      | 1 +
 src/solver_options.jl | 3 +++
 src/solvers.jl        | 9 +++++++++
 test/runtests.jl      | 8 ++++++++
 5 files changed, 22 insertions(+)

diff --git a/gen/solver_options.jl b/gen/solver_options.jl
index b8a01ba..082c2f1 100644
--- a/gen/solver_options.jl
+++ b/gen/solver_options.jl
@@ -28,6 +28,7 @@ function generate_options(io, structname, prefixes...)
         print(io, "        $(first ? "" : "else")if k === :$(k)")
         println(io)
         if k == "Precond"
+            println(io, "            Internals.set_precond_defaults(v)")
             println(io, "            Internals.set_precond(s, v)")
         elseif nargs == 1
             println(io, "            @check ", n, "(solver)")
diff --git a/src/Internals.jl b/src/Internals.jl
index 208e8e3..c733d5b 100644
--- a/src/Internals.jl
+++ b/src/Internals.jl
@@ -12,5 +12,6 @@ function set_options end
 function solve_func end
 function setup_func end
 function set_precond end
+function set_precond_defaults end
 
 end # module Internals
diff --git a/src/solver_options.jl b/src/solver_options.jl
index 11248ed..9fc7287 100644
--- a/src/solver_options.jl
+++ b/src/solver_options.jl
@@ -18,6 +18,7 @@ function Internals.set_options(s::BiCGSTAB, kwargs)
         elseif k === :MinIter
             @check HYPRE_ParCSRBiCGSTABSetMinIter(solver, v)
         elseif k === :Precond
+            Internals.set_precond_defaults(v)
             Internals.set_precond(s, v)
         elseif k === :PrintLevel
             @check HYPRE_ParCSRBiCGSTABSetPrintLevel(solver, v)
@@ -308,6 +309,7 @@ function Internals.set_options(s::GMRES, kwargs)
         elseif k === :MinIter
             @check HYPRE_ParCSRGMRESSetMinIter(solver, v)
         elseif k === :Precond
+            Internals.set_precond_defaults(v)
             Internals.set_precond(s, v)
         elseif k === :PrintLevel
             @check HYPRE_ParCSRGMRESSetPrintLevel(solver, v)
@@ -341,6 +343,7 @@ function Internals.set_options(s::PCG, kwargs)
         elseif k === :MaxIter
             @check HYPRE_ParCSRPCGSetMaxIter(solver, v)
         elseif k === :Precond
+            Internals.set_precond_defaults(v)
             Internals.set_precond(s, v)
         elseif k === :PrintLevel
             @check HYPRE_ParCSRPCGSetPrintLevel(solver, v)
diff --git a/src/solvers.jl b/src/solvers.jl
index be03d97..116532b 100644
--- a/src/solvers.jl
+++ b/src/solvers.jl
@@ -7,6 +7,9 @@ Abstract super type of all the wrapped HYPRE solvers.
 """
 abstract type HYPRESolver end
 
+# Fallback for the solvers that doesn't have required defaults
+Internals.set_precond_defaults(::HYPRESolver) = nothing
+
 # Generic fallback allocating a zero vector as initial guess
 # TODO: This should allocate x using the owned cols instead of rows of A/b, but currently
 #       it is assumed these are always equivalent.
@@ -142,6 +145,12 @@ end
 Internals.solve_func(::BoomerAMG) = HYPRE_BoomerAMGSolve
 Internals.setup_func(::BoomerAMG) = HYPRE_BoomerAMGSetup
 
+function Internals.set_precond_defaults(amg::BoomerAMG)
+    defaults = (; Tol = 0.0, MaxIter = 1)
+    Internals.set_options(amg, pairs(defaults))
+    return nothing
+end
+
 
 #########
 # GMRES #
diff --git a/test/runtests.jl b/test/runtests.jl
index b0a71e4..f07d05a 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -312,6 +312,14 @@ end
     x_h = HYPRE.solve(bicg, A_h, b_h)
     copy!(x, x_h)
     @test x ≈ A \ b atol=tol
+    # Tests Internals.set_precond_defaults for BoomerAMG
+    precond = HYPRE.BoomerAMG()
+    bicg = HYPRE.BiCGSTAB(; Tol = tol, Precond = precond)
+    x_h = HYPREVector(zeros(100))
+    HYPRE.solve!(bicg, x_h, A_h, b_h)
+    copy!(x, x_h)
+    # Test result with direct solver
+    @test x ≈ A \ b atol=tol
 end
 
 @testset "BoomerAMG" begin