Merge branch 'feature/amg' into 'develop'

Plug PETSc's AMG preconditioner

See merge request !57

src/algebra/LinearSolver.cpp

@@ -88,6 +88,7 @@ struct LinearSolver::Internals
   {
     switch (precond) {
     case LSPrecond::none:
+    case LSPrecond::amg:
     case LSPrecond::diagonal:
     case LSPrecond::incomplete_choleski:
     case LSPrecond::incomplete_LU: {
@@ -244,6 +245,10 @@ struct LinearSolver::Internals
 
     if (not direct_solver) {
       switch (options.precond()) {
+      case LSPrecond::amg: {
+        PCSetType(pc, PCGAMG);
+        break;
+      }
       case LSPrecond::diagonal: {
         PCSetType(pc, PCJACOBI);
         break;

src/algebra/LinearSolverOptions.hpp

@@ -37,6 +37,7 @@ enum class LSPrecond : int8_t
   diagonal,
   incomplete_choleski,
   incomplete_LU,
+  amg,
   //
   LS__end
 };
@@ -101,6 +102,9 @@ name(const LSPrecond precond)
   case LSPrecond::incomplete_LU: {
     return "ILU";
   }
+  case LSPrecond::amg: {
+    return "AMG";
+  }
   case LSPrecond::LS__end: {
   }
   }