CCTK_REAL max_diff TYPE=SCALAR TIMELEVELS=1 "difference to expected value"

  WRITES: TestProlongate::data(interior)

  WRITES: data(interior) max_diff(interior)

SCHEDULE TestProlongate_Check IN CCTK_ANALYSIS
{
  LANG: C
  READS: max_diff(interior)
  WRITES: max_diff(interior)
} "Compute max difference"

#include <algorithm>

  *max_diff = 0.;

extern "C" void TestProlongate_Check(CCTK_ARGUMENTS) {
  DECLARE_CCTK_PARAMETERS;
  DECLARE_CCTK_ARGUMENTS;
  // there is no reduction yet, so for now I require that only 1 MPI rank be in
  // use
  assert(CCTK_nProcs(cctkGH) == 1 && "Must be single rank");
  // get prolongation order from driver, the parmeter is private since really
  // there is normally no reason to depend on it
  int order_type;
  const void *order_p = CCTK_ParameterGet("prolongation_order", "AMReX",
                                          &order_type);
  assert(order_p);
  assert(order_type == PARAMETER_INT);
  const CCTK_INT operator_order = *static_cast<const CCTK_INT*>(order_p);
  CCTK_REAL my_max_diff = 0;
  Loop::loop_int<1, 1, 1>(cctkGH, [&](const Loop::PointDesc &p) {
    const CCTK_REAL diff = fabs(data[p.idx] -
                                pow(p.x * p.y * p.z, operator_order));
    my_max_diff = max(diff, my_max_diff);
  });
  #pragma omp critical
  {
    *max_diff = max(*max_diff, my_max_diff);
  }
}