simplify empty matrix test & reduce clutter output

src/hyteg/ginkgo/GinkgoCGSolver.hpp

@@ -435,7 +435,7 @@ class GinkgoCGSolver : public Solver< OperatorType >
       {
          auto [start, end] = local_range( num_local_dofs, comm_ );
          part_             = gko::share( gko::distributed::Partition<>::build_from_local_range( host_exec_, start, end, comm_ ) );
-         if ( printInfo_ )
+         if ( printInfo_ && num_local_dofs )
          {
             WALBERLA_LOG_INFO( "[Ginkgo CG] Rank " << rank << " -> local size: " << num_local_dofs << " local range: " << start
                                                    << "-" << end );
@@ -508,7 +508,7 @@ class GinkgoCGSolver : public Solver< OperatorType >
             host_matrix_->convert_to( gko::lend( matrix_ ) );
             x.getStorage()->getTimingTree()->stop( "Ginkgo CG matrix-gather" );
 
-            if ( matrix_->get_size()[0] > 0 && matrix_->get_size()[1] > 0 )
+            if ( matrix_->get_size() )
             {
                auto          old_buffer = std::cout.rdbuf();
                std::ofstream dev_null( "/dev/null" );
@@ -540,7 +540,7 @@ class GinkgoCGSolver : public Solver< OperatorType >
          x.getStorage()->getTimingTree()->stop( "Ginkgo CG Solver gather" );
 
          x.getStorage()->getTimingTree()->start( "Ginkgo CG Solver Apply" );
-         if ( matrix_->get_size()[0] > 0 && matrix_->get_size()[1] > 0 )
+         if ( matrix_->get_size() )
          {
             solver_->apply( gko::lend( global_rhs ), gko::lend( global_x0 ) );
          }