Added trap so that if PPM reconstruction is selected, NGHOST must be …

…set to 3 or

larger.  Also made nghost an option in configure script.

configure.py

@@ -9,9 +9,10 @@
 # The following options are implememted:
 #   -h  --help        help message
 #   --prob=name       use src/pgen/name.cpp as the problem generator
-#   --coord=choice    use choice as the coordinate system
-#   --eos=choice      use choice as the equation of state
-#   --flux=choice     use choice as the Riemann solver
+#   --coord=xxx       use xxx as the coordinate system
+#   --eos=xxx         use xxx as the equation of state
+#   --flux=xxx        use xxx as the Riemann solver
+#   --nghost=xxx      set NGHOST=xxx
 #   -b                enable magnetic fields
 #   -s                enable special relativity
 #   -g                enable general relativity
@@ -24,8 +25,8 @@
 #   --hdf5_path=path  path to HDF5 libraries (requires the HDF5 library)
 #   -fft              enable FFT (requires the FFTW library)
 #   --fftw_path=path  path to FFTW libraries (requires the FFTW library)
-#   --grav=choice     use choice as the self-gravity solver
-#   --cxx=choice      use choice as the C++ compiler
+#   --grav=xxx        use xxx as the self-gravity solver
+#   --cxx=xxx         use xxx as the C++ compiler
 #   --ccmd=name       use name as the command to call the C++ compiler
 #   --include=path    use -Ipath when compiling
 #   --lib=path        use -Lpath when linking
@@ -75,6 +76,11 @@
     choices=['default','hlle','hllc','hlld','roe','llf'],
     help='select Riemann solver')
 
+# --nghost=[value] argument
+parser.add_argument('--nghost',
+    default='2',
+    help='set number of ghost zones')
+
 # -b argument
 parser.add_argument('-b',
     action='store_true',
@@ -245,6 +251,9 @@
 # --flux=[name] argument
 definitions['RSOLVER'] = makefile_options['RSOLVER_FILE'] = args['flux']
 
+# --nghost=[value] argument
+definitions['NUMBER_GHOST_CELLS'] = args['nghost']
+
 # -b argument
 # set variety of macros based on whether MHD/hydro or adi/iso are defined
 if args['b']:

src/defs.hpp.in

@@ -71,7 +71,7 @@
 #define NHYDRO @NHYDRO_VARIABLES@
 #define NFIELD @NFIELD_VARIABLES@
 #define NWAVE @NWAVE_VALUE@
-#define NGHOST 2
+#define NGHOST @NUMBER_GHOST_CELLS@
 #define MAX_NSTEP 4
 
 //----------------------------------------------------------------------------------------

src/reconstruct/reconstruction.cpp

@@ -47,6 +47,15 @@ Reconstruction::Reconstruction(MeshBlock *pmb, ParameterInput *pin)
     throw std::runtime_error(msg.str().c_str());
   }
 
+  // check that there are the necessary number of ghost zones
+  if (xorder == 3 && (NGHOST) < 3) {
+    std::stringstream msg;
+    msg << "### FATAL ERROR in Reconstruction constructor" << std::endl
+        << "xorder=" << xorder << " (PPM) reconstruction selected, but nghost=" <<
+        NGHOST << std::endl << "Reconfigure with --nghost=XXX with XXX > 2" << std::endl;
+    throw std::runtime_error(msg.str().c_str());
+  }
+
   // Allocate memory for scratch arrays used in PLM and PPM
   int ncells1 = pmb->block_size.nx1 + 2*(NGHOST);
   scr01_i_.NewAthenaArray(ncells1);

src/utils/show_config.cpp

@@ -63,6 +63,7 @@ void ShowConfig(void)
   } else {
     std::cout<<"  Floating point precision:   double" << std::endl;
   }
+  std::cout<<"  Number of ghost cells:      " << NGHOST << std::endl;
 #ifdef MPI_PARALLEL
   std::cout<<"  MPI parallelism:            ON" << std::endl;
 #else