Post Timestep Calculations for Pmax

[Soobin120596]

Hello everone! I am a beginner with detonation simulations using PeleC. I was trying to perform some manipulations at runtime using the problem_post_timestep function, such as calucating the max pressure between two instants. I saw the answers from RSuryaNarayan in Q&A 862(#862).
I have added similar functions, but I don't know how to output the resulting Pmax. Any pointers or suggestions would be much appreciated. Thank you very much！
I.problem_post_timestep in prob.cpp:

PeleC::problem_post_timestep()
{
  //Get old and new states
  amrex::MultiFab& S_new = get_new_data(State_Type);
  amrex::MultiFab& S_old = get_old_data(State_Type);

  //MFIter to iterate across the domain
  for (amrex::MFIter mfi(S_new, amrex::TilingIfNotGPU()); mfi.isValid();++mfi)
  {
    const amrex::Box& box = mfi.tilebox();

    auto sfab_new = S_new.array(mfi);//new state
    auto sfab_old = S_old.array(mfi);//new state

    const auto geomdata = geom.data();

    const amrex::Real* prob_lo = geomdata.ProbLo();
    const amrex::Real* dx = geomdata.CellSize();
    const ProbParmDevice* lprobparm = d_prob_parm_device;

    if(lprobparm->PostStep>0)
    {
      amrex::ParallelFor(box, [=] AMREX_GPU_DEVICE(int i, int j, int k) noexcept {
      pc_poststep(i, j, k, sfab_new, sfab_old, geomdata, *lprobparm);
      });
    }
  }
}

II.pc_poststep in prob.H:

AMREX_FORCE_INLINE
void
pc_poststep(
  int i,
  int j,
  int k,
  amrex::Array4<amrex::Real> const& state_new,
  amrex::Array4<amrex::Real> const& state_old,
  amrex::GeometryData const& geomdata,
  ProbParmDevice const& prob_parm)
{
  amrex::Real P_old, massfrac_old[NUM_SPECIES], T_old, rho_old, P_new, massfrac_new[NUM_SPECIES], T_new, rho_new;

  T_old = state_old(i, j, k, UTEMP); //T_old 
  T_new = state_new(i, j, k, UTEMP); //T_new 

  rho_old = state_old(i, j, k, URHO); //rho_old
  rho_new = state_new(i, j, k, URHO); //rho_new

  for (int n = 0; n < NUM_SPECIES; n++) 
  {
    massfrac_old[n] = state_old(i, j, k, UFS + n) / rho_old;
  }

  for (int n = 0; n < NUM_SPECIES; n++) 
  {
    massfrac_new[n] = state_new(i, j, k, UFS + n) / rho_new;
  }

  auto eos = pele::physics::PhysicsType::eos();
  eos.RTY2P(rho_old, T_old, massfrac_old, P_old);//calculate according eos
  eos.RTY2P(rho_new, T_new, massfrac_new, P_new);

  amrex::Real max_pressure_value = amrex::max(P_old, P_new);//

  //what shoud I do then? How can I output the max pressure value?????
}```

[Soobin120596]

I saw that can achieve by this way in openfoam, but I don’t know how to achieve it in PeleC
for (label cellI=0; cellI<mesh.C().size(); cellI++)
{
if(maxp[cellI]<p[cellI]) maxp[cellI] = p[cellI] ;
}

maxp.writeOpt() = IOobject::AUTO_WRITE;