More guards

examples/miscellaneous/miscellaneous_ex17/miscellaneous_ex17.C

@@ -29,14 +29,12 @@
 #include "libmesh/fe.h"
 
 // Define Gauss quadrature rules.
-#include "libmesh/petsc_solver_exception.h"
-#include "libmesh/petsc_vector.h"
 #include "libmesh/quadrature_gauss.h"
 
 // Define useful datatypes for finite element
 // matrix and vector components.
-#include "libmesh/petsc_matrix.h"
 #include "libmesh/numeric_vector.h"
+#include "libmesh/sparse_matrix.h"
 #include "libmesh/dense_matrix.h"
 #include "libmesh/dense_vector.h"
 #include "libmesh/elem.h"
@@ -45,7 +43,11 @@
 // Define the DofMap, which handles degree of freedom
 // indexing.
 #include "libmesh/dof_map.h"
+
 #ifdef LIBMESH_HAVE_PETSC
+// include PETSc headers
+#include "libmesh/petsc_matrix.h"
+#include "libmesh/petsc_vector.h"
 #include "petscksp.h"
 #endif
 
@@ -67,9 +69,6 @@ int main (int argc, char ** argv)
   // Initialize libraries, like in example 2.
   LibMeshInit init (argc, argv);
 
-  // This example requires a linear solver package.
-  libmesh_example_requires(libMesh::default_solver_package() == PETSC_SOLVERS, "--enable-petsc");
-
   // Brief message to the user regarding the program name
   // and command line arguments.
   libMesh::out << "Running " << argv[0];
@@ -116,7 +115,11 @@ int main (int argc, char ** argv)
 
   // Add the preconditioner matrix
   auto & pre_sparse_matrix = system.add_matrix("preconditioner");
+#ifdef LIBMESH_HAVE_PETSC
+#if PETSC_RELEASE_GREATER_EQUALS(3, 19, 0)
   pre_sparse_matrix.use_hash_table(true);
+#endif
+#endif
 
   // Initialize the data structures for the equation system.
   equation_systems.init();
@@ -149,6 +152,8 @@ int main (int argc, char ** argv)
 
   // solve
   solve();
+
+  // MatResetHash added in PETSc version 3.23
 #if !PETSC_VERSION_LESS_THAN(3, 23, 0)
   // reset the memory
   // sys_matrix.reset_memory(); # See https://gitlab.com/petsc/petsc/-/merge_requests/8063