Add ComputeMaxStep() function in WarpXInitData (#1712)

* Add ComputeMaxStep() function in WarpXInitData

* Avoid overflow in the static_cast

* Change overflow handling and update stop_time constistently with max_step

1 files changed, 0 insertions, 52 deletions

diff --git a/Source/Evolve/WarpXEvolve.cpp b/Source/Evolve/WarpXEvolve.cpp
index 2f04310a5..e48166cf1 100644
--- a/Source/Evolve/WarpXEvolve.cpp
+++ b/Source/Evolve/WarpXEvolve.cpp
@@ -30,10 +30,6 @@ WarpX::Evolve (int numsteps)
 
     Real cur_time = t_new[0];
 
-    if (do_compute_max_step_from_zmax) {
-        computeMaxStepBoostAccelerator(geom[0]);
-    }
-
     int numsteps_max;
     if (numsteps < 0) {  // Note that the default argument is numsteps = -1
         numsteps_max = max_step;
@@ -648,54 +644,6 @@ WarpX::PushParticlesandDepose (int lev, amrex::Real cur_time, DtType a_dt_type,
 #endif
 }
 
-/* \brief computes max_step for wakefield simulation in boosted frame.
- * \param geom: Geometry object that contains simulation domain.
- *
- * max_step is set so that the simulation stop when the lower corner of the
- * simulation box passes input parameter zmax_plasma_to_compute_max_step.
- */
-void
-WarpX::computeMaxStepBoostAccelerator(const amrex::Geometry& a_geom){
-    // Sanity checks: can use zmax_plasma_to_compute_max_step only if
-    // the moving window and the boost are all in z direction.
-    AMREX_ALWAYS_ASSERT_WITH_MESSAGE(
-        WarpX::moving_window_dir == AMREX_SPACEDIM-1,
-        "Can use zmax_plasma_to_compute_max_step only if " +
-        "moving window along z. TODO: all directions.");
-    if (gamma_boost > 1){
-        AMREX_ALWAYS_ASSERT_WITH_MESSAGE(
-            (WarpX::boost_direction[0]-0)*(WarpX::boost_direction[0]-0) +
-            (WarpX::boost_direction[1]-0)*(WarpX::boost_direction[1]-0) +
-            (WarpX::boost_direction[2]-1)*(WarpX::boost_direction[2]-1) < 1.e-12,
-            "Can use zmax_plasma_to_compute_max_step in boosted frame only if " +
-            "warpx.boost_direction = z. TODO: all directions.");
-    }
-
-    // Lower end of the simulation domain. All quantities are given in boosted
-    // frame except zmax_plasma_to_compute_max_step.
-    const Real zmin_domain_boost = a_geom.ProbLo(AMREX_SPACEDIM-1);
-    // End of the plasma: Transform input argument
-    // zmax_plasma_to_compute_max_step to boosted frame.
-    const Real len_plasma_boost = zmax_plasma_to_compute_max_step/gamma_boost;
-    // Plasma velocity
-    const Real v_plasma_boost = -beta_boost * PhysConst::c;
-    // Get time at which the lower end of the simulation domain passes the
-    // upper end of the plasma (in the z direction).
-    const Real interaction_time_boost = (len_plasma_boost-zmin_domain_boost)/
-        (moving_window_v-v_plasma_boost);
-    // Divide by dt, and update value of max_step.
-    int computed_max_step;
-    if (do_subcycling){
-        computed_max_step = static_cast<int>(interaction_time_boost/dt[0]);
-    } else {
-        computed_max_step =
-            static_cast<int>(interaction_time_boost/dt[maxLevel()]);
-    }
-    max_step = computed_max_step;
-    Print()<<"max_step computed in computeMaxStepBoostAccelerator: "
-           <<computed_max_step<<std::endl;
-}
-
 /* \brief Apply perfect mirror condition inside the box (not at a boundary).
  * In practice, set all fields to 0 on a section of the simulation domain
  * (as for a perfect conductor with a given thickness).