Merge branch 'gear_pressure_floor' into 'master'

Gear pressure floor

See merge request !811

configure.ac

@@ -1327,6 +1327,7 @@ with_subgrid_cooling=none
 with_subgrid_chemistry=none
 with_subgrid_tracers=none
 with_subgrid_entropy_floor=none
+with_subgrid_pressure_floor=none
 with_subgrid_stars=none
 with_subgrid_star_formation=none
 with_subgrid_feedback=none
@@ -1338,10 +1339,9 @@ case "$with_subgrid" in
    none)
    ;;
    GEAR)
-	with_subgrid_cooling=grackle
+	with_subgrid_cooling=grackle_0
 	with_subgrid_chemistry=GEAR
-	with_subgrid_tracers=none
-	with_subgrid_entropy_floor=none
+	with_subgrid_pressure_floor=GEAR
 	with_subgrid_stars=GEAR
 	with_subgrid_star_formation=GEAR
 	with_subgrid_feedback=none
@@ -1646,7 +1646,8 @@ esac
 #  Cooling function
 AC_ARG_WITH([cooling],
    [AS_HELP_STRING([--with-cooling=<function>],
-      [cooling function @<:@none, const-du, const-lambda, EAGLE, grackle, grackle1, grackle2, grackle3 default: none@:>@]
+      [cooling function @<:@none, const-du, const-lambda, EAGLE, grackle_* default: none@:>@.
+      For Grackle, you need to provide the primordial chemistry parameter (e.g. grackle_0)]
    )],
    [with_cooling="$withval"],
    [with_cooling="none"]
@@ -1673,21 +1674,10 @@ case "$with_cooling" in
    compton)
       AC_DEFINE([COOLING_COMPTON], [1], [Compton cooling off the CMB])
    ;;
-   grackle)
+   grackle_*)
       AC_DEFINE([COOLING_GRACKLE], [1], [Cooling via the grackle library])
-      AC_DEFINE([COOLING_GRACKLE_MODE], [0], [Grackle chemistry network, mode 0])
-   ;;
-   grackle1)
-      AC_DEFINE([COOLING_GRACKLE], [1], [Cooling via the grackle library])
-      AC_DEFINE([COOLING_GRACKLE_MODE], [1], [Grackle chemistry network, mode 1])
-   ;;
-   grackle2)
-      AC_DEFINE([COOLING_GRACKLE], [1], [Cooling via the grackle library])
-      AC_DEFINE([COOLING_GRACKLE_MODE], [2], [Grackle chemistry network, mode 2])
-   ;;
-   grackle3)
-      AC_DEFINE([COOLING_GRACKLE], [1], [Cooling via the grackle library])
-      AC_DEFINE([COOLING_GRACKLE_MODE], [3], [Grackle chemistry network, mode 3])
+      primordial_chemistry=${with_cooling:8}
+      AC_DEFINE_UNQUOTED([COOLING_GRACKLE_MODE], [$primordial_chemistry], [Grackle chemistry network])
    ;;
    EAGLE)
       AC_DEFINE([COOLING_EAGLE], [1], [Cooling following the EAGLE model])
@@ -1922,6 +1912,35 @@ case "$with_entropy_floor" in
    ;;
 esac 
 
+#  Pressure floor
+AC_ARG_WITH([pressure-floor], 
+    [AS_HELP_STRING([--with-pressure-floor=<floor>],
+       [pressure floor @<:@none, GEAR, default: none@:>@
+       The hydro model needs to be compatible.]
+    )],
+    [with_pressure_floor="$withval"],
+    [with_pressure_floor="none"]
+)
+if test "$with_subgrid" != "none"; then
+   if test "$with_pressure_floor" != "none"; then
+      AC_MSG_ERROR([Cannot provide with-subgrid and with-pressure-floor together])
+   else
+      with_pressure_floor="$with_subgrid_pressure_floor"
+   fi
+fi
+
+case "$with_pressure_floor" in
+   none)
+      AC_DEFINE([PRESSURE_FLOOR_NONE], [1], [No pressure floor])
+   ;;
+   GEAR)
+      AC_DEFINE([PRESSURE_FLOOR_GEAR], [1], [GEAR pressure floor])
+   ;;
+   *)
+      AC_MSG_ERROR([Unknown pressure floor model])
+   ;;
+esac 
+
 #  Star formation
 AC_ARG_WITH([star-formation], 
     [AS_HELP_STRING([--with-star-formation=<sfm>],
@@ -2056,6 +2075,7 @@ AC_MSG_RESULT([
    External potential  : $with_potential
 
    Entropy floor        : $with_entropy_floor
+   Pressure floor       : $with_pressure_floor
    Cooling function     : $with_cooling
    Chemistry            : $with_chemistry
    Tracers              : $with_tracers

doc/RTD/source/SubgridModels/GEAR/index.rst

@@ -5,6 +5,29 @@
 GEAR model
 ===========
 
+Pressure Floor
+~~~~~~~~~~~~~~
+
+In order to avoid the artificial collapse of unresolved clumps, a minimum in pressure is applied to the particles.
+This additional pressure can be seen as the pressure due to unresolved hydrodynamics turbulence and is given by:
+
+.. math::
+    P_\textrm{Jeans} = \frac{\rho}{\gamma} \left( \frac{4}{\pi} G h^2 \rho N_\textrm{Jeans}^{2/3} - \sigma^2 \right)
+
+where :math:`\rho` is the density, :math:`\gamma` the adiabatic index, :math:`G` is the gravitational constant,
+:math:`h` the smoothing length, :math:`N_\textrm{Jeans}` is the number of particle required in order to resolve a clump and
+:math:`\sigma` the velocity dispersion.
+
+
+This must be directly implemented into the hydro schemes, therefore only a subset of schemes (Gadget-2 and Pressure-Energy) are currently implemented.
+In order to implement it, you need equation 12 in `Hopkins 2013 <https://arxiv.org/abs/1206.5006>`_:
+
+.. math::
+   m_i \frac{\mathrm{d}v_i}{\mathrm{d}t} = - \sum_j x_i x_j \left[ \frac{P_i}{y_i^2} f_{ij} \nabla_i W_{ij}(h_i) + \frac{P_j}{y_j^2} f_{ji} \nabla_j W_{ji}(h_j) \right]
+
+and simply replace the :math:`P_i, P_j` by the pressure with the floor.
+Here the :math:`x, y` are simple weights that should never have the pressure floor included even if they are related to the pressure (e.g. pressure-entropy).
+
 
 Cooling: Grackle
 ~~~~~~~~~~~~~~~~

examples/SmallCosmoVolume/SmallCosmoVolume_cooling/small_cosmo_volume.yml

@@ -99,3 +99,6 @@ GrackleCooling:
 
 GearChemistry:
   InitialMetallicity: 0.01295
+
+GEARPressureFloor:
+  Jeans_factor: 10.       # Number of particles required to suppose a resolved clump and avoid the pressure floor.

examples/main.c

@@ -777,6 +777,13 @@ int main(int argc, char *argv[]) {
     else
       bzero(&entropy_floor, sizeof(struct entropy_floor_properties));
 
+    /* Initialise the pressure floor */
+    if (with_hydro)
+      pressure_floor_init(&pressure_floor_props, &prog_const, &us,
+                          &hydro_properties, params);
+    else
+      bzero(&pressure_floor_props, sizeof(struct pressure_floor_properties));
+
     /* Initialise the stars properties */
     if (with_stars)
       stars_props_init(&stars_properties, &prog_const, &us, params,

examples/parameter_example.yml

@@ -285,6 +285,11 @@ EAGLEEntropyFloor:
   Cool_temperature_norm_K:         8000      # Temperature of the EAGLE Cool limiter entropy floor at the density threshold expressed in Kelvin.
   Cool_gamma_effective:            1.        # Slope the of the EAGLE Cool limiter entropy floor
   
+# Parameters related to pressure floors    ----------------------------------------------
+
+GEARPressureFloor:
+  Jeans_factor: 10.       # Number of particles required to suppose a resolved clump and avoid the pressure floor.
+
 # Parameters related to cooling function  ----------------------------------------------
 
 # Constant du/dt cooling function

src/Makefile.am

@@ -79,7 +79,7 @@ AM_SOURCES = space.c runner.c queue.c task.c cell.c engine.c engine_maketasks.c
     collectgroup.c hydro_space.c equation_of_state.c \
     chemistry.c cosmology.c restart.c mesh_gravity.c velociraptor_interface.c \
     outputlist.c velociraptor_dummy.c logger_io.c memuse.c fof.c \
-    hashmap.c \
+    hashmap.c pressure_floor.c \
     $(EAGLE_COOLING_SOURCES) $(EAGLE_FEEDBACK_SOURCES)
 
 # Include files for distribution, not installation.

src/cooling/grackle/cooling.h

@@ -52,7 +52,7 @@ static gr_float cooling_time(
     const struct unit_system* restrict us,
     const struct cosmology* restrict cosmo,
     const struct cooling_function_data* restrict cooling,
-    const struct part* restrict p, const struct xpart* restrict xp);
+    const struct part* restrict p, struct xpart* restrict xp);
 static gr_float cooling_new_energy(
     const struct phys_const* restrict phys_const,
     const struct unit_system* restrict us,
@@ -573,7 +573,7 @@ __attribute__((always_inline)) INLINE static gr_float cooling_time(
     const struct unit_system* restrict us,
     const struct cosmology* restrict cosmo,
     const struct cooling_function_data* restrict cooling,
-    const struct part* restrict p, const struct xpart* restrict xp) {
+    const struct part* restrict p, struct xpart* restrict xp) {
 
   /* set current time */
   code_units units = cooling->units;

src/hydro/Gadget2/hydro.h

@@ -41,6 +41,7 @@
 #include "hydro_space.h"
 #include "kernel_hydro.h"
 #include "minmax.h"
+#include "pressure_floor.h"
 
 #include "./hydro_parameters.h"
 
@@ -109,7 +110,8 @@ hydro_get_drifted_physical_internal_energy(const struct part *restrict p,
 __attribute__((always_inline)) INLINE static float hydro_get_comoving_pressure(
     const struct part *restrict p) {
 
-  return gas_pressure_from_entropy(p->rho, p->entropy);
+  const float comoving_pressure = gas_pressure_from_entropy(p->rho, p->entropy);
+  return pressure_floor_get_pressure(p, p->rho, comoving_pressure);
 }
 
 /**
@@ -121,7 +123,10 @@ __attribute__((always_inline)) INLINE static float hydro_get_comoving_pressure(
 __attribute__((always_inline)) INLINE static float hydro_get_physical_pressure(
     const struct part *restrict p, const struct cosmology *cosmo) {
 
-  return gas_pressure_from_entropy(p->rho * cosmo->a3_inv, p->entropy);
+  const float phys_pressure =
+      gas_pressure_from_entropy(p->rho * cosmo->a3_inv, p->entropy);
+  const float phys_rho = hydro_get_physical_density(p, cosmo);
+  return pressure_floor_get_pressure(p, phys_rho, phys_pressure);
 }
 
 /**
@@ -388,13 +393,15 @@ hydro_set_drifted_physical_internal_energy(struct part *p,
   const float rho_inv = 1.f / p->rho;
 
   /* Compute the pressure */
-  const float pressure = gas_pressure_from_entropy(p->rho, p->entropy);
+  float comoving_pressure = gas_pressure_from_entropy(p->rho, p->entropy);
+  comoving_pressure = pressure_floor_get_pressure(p, p->rho, comoving_pressure);
 
   /* Compute the sound speed */
-  const float soundspeed = gas_soundspeed_from_pressure(p->rho, pressure);
+  const float soundspeed =
+      gas_soundspeed_from_pressure(p->rho, comoving_pressure);
 
   /* Divide the pressure by the density squared to get the SPH term */
-  const float P_over_rho2 = pressure * rho_inv * rho_inv;
+  const float P_over_rho2 = comoving_pressure * rho_inv * rho_inv;
 
   /* Update variables. */
   p->force.P_over_rho2 = P_over_rho2;
@@ -591,13 +598,15 @@ __attribute__((always_inline)) INLINE static void hydro_prepare_force(
   const float abs_div_physical_v = fabsf(div_physical_v);
 
   /* Compute the pressure */
-  const float pressure = gas_pressure_from_entropy(p->rho, p->entropy);
+  float comoving_pressure = gas_pressure_from_entropy(p->rho, p->entropy);
+  comoving_pressure = pressure_floor_get_pressure(p, p->rho, comoving_pressure);
 
   /* Compute the sound speed */
-  const float soundspeed = gas_soundspeed_from_pressure(p->rho, pressure);
+  const float soundspeed =
+      gas_soundspeed_from_pressure(p->rho, comoving_pressure);
 
   /* Divide the pressure by the density squared to get the SPH term */
-  const float P_over_rho2 = pressure * rho_inv * rho_inv;
+  const float P_over_rho2 = comoving_pressure * rho_inv * rho_inv;
 
   /* Compute the Balsara switch */
   /* Pre-multiply in the AV factor; hydro_props are not passed to the iact
@@ -665,14 +674,16 @@ __attribute__((always_inline)) INLINE static void hydro_reset_predicted_values(
   p->entropy = xp->entropy_full;
 
   /* Re-compute the pressure */
-  const float pressure = gas_pressure_from_entropy(p->rho, p->entropy);
+  float comoving_pressure = gas_pressure_from_entropy(p->rho, p->entropy);
+  comoving_pressure = pressure_floor_get_pressure(p, p->rho, comoving_pressure);
 
   /* Compute the new sound speed */
-  const float soundspeed = gas_soundspeed_from_pressure(p->rho, pressure);
+  const float soundspeed =
+      gas_soundspeed_from_pressure(p->rho, comoving_pressure);
 
   /* Divide the pressure by the density squared to get the SPH term */
   const float rho_inv = 1.f / p->rho;
-  const float P_over_rho2 = pressure * rho_inv * rho_inv;
+  const float P_over_rho2 = comoving_pressure * rho_inv * rho_inv;
 
   /* Update variables */
   p->force.soundspeed = soundspeed;
@@ -730,14 +741,16 @@ __attribute__((always_inline)) INLINE static void hydro_predict_extra(
     p->rho *= expf(w2);
 
   /* Re-compute the pressure */
-  const float pressure = gas_pressure_from_entropy(p->rho, p->entropy);
+  float comoving_pressure = gas_pressure_from_entropy(p->rho, p->entropy);
+  comoving_pressure = pressure_floor_get_pressure(p, p->rho, comoving_pressure);
 
   /* Compute the new sound speed */
-  const float soundspeed = gas_soundspeed_from_pressure(p->rho, pressure);
+  const float soundspeed =
+      gas_soundspeed_from_pressure(p->rho, comoving_pressure);
 
   /* Divide the pressure by the density squared to get the SPH term */
   const float rho_inv = 1.f / p->rho;
-  const float P_over_rho2 = pressure * rho_inv * rho_inv;
+  const float P_over_rho2 = comoving_pressure * rho_inv * rho_inv;
 
   /* Update variables */
   p->force.soundspeed = soundspeed;
@@ -840,14 +853,16 @@ __attribute__((always_inline)) INLINE static void hydro_convert_quantities(
   }
 
   /* Compute the pressure */
-  const float pressure = gas_pressure_from_entropy(p->rho, p->entropy);
+  float comoving_pressure = gas_pressure_from_entropy(p->rho, p->entropy);
+  comoving_pressure = pressure_floor_get_pressure(p, p->rho, comoving_pressure);
 
   /* Compute the sound speed */
-  const float soundspeed = gas_soundspeed_from_pressure(p->rho, pressure);
+  const float soundspeed =
+      gas_soundspeed_from_pressure(p->rho, comoving_pressure);
 
   /* Divide the pressure by the density squared to get the SPH term */
   const float rho_inv = 1.f / p->rho;
-  const float P_over_rho2 = pressure * rho_inv * rho_inv;
+  const float P_over_rho2 = comoving_pressure * rho_inv * rho_inv;
 
   p->force.soundspeed = soundspeed;
   p->force.P_over_rho2 = P_over_rho2;

src/hydro/PressureEnergy/hydro.h

@@ -46,6 +46,7 @@
 #include "hydro_space.h"
 #include "kernel_hydro.h"
 #include "minmax.h"
+#include "pressure_floor.h"
 
 #include "./hydro_parameters.h"
 
@@ -221,7 +222,9 @@ hydro_get_comoving_soundspeed(const struct part *restrict p) {
 
   /* Compute the sound speed -- see theory section for justification */
   /* IDEAL GAS ONLY -- P-U does not work with generic EoS. */
-  const float square_rooted = sqrtf(hydro_gamma * p->pressure_bar / p->rho);
+  const float comoving_pressure =
+      pressure_floor_get_pressure(p, p->rho, p->pressure_bar);
+  const float square_rooted = sqrtf(hydro_gamma * comoving_pressure / p->rho);
 
   return square_rooted;
 }
@@ -236,7 +239,10 @@ __attribute__((always_inline)) INLINE static float
 hydro_get_physical_soundspeed(const struct part *restrict p,
                               const struct cosmology *cosmo) {
 
-  return cosmo->a_factor_sound_speed * p->force.soundspeed;
+  const float phys_rho = hydro_get_physical_density(p, cosmo);
+
+  return pressure_floor_get_pressure(
+      p, phys_rho, cosmo->a_factor_sound_speed * p->force.soundspeed);
 }
 
 /**
@@ -640,10 +646,15 @@ __attribute__((always_inline)) INLINE static void hydro_prepare_force(
                              hydro_one_over_gamma_minus_one) /
                             (1.f + common_factor * p->density.wcount_dh);
 
+  /* Get the pressures */
+  const float comoving_pressure_with_floor =
+      pressure_floor_get_pressure(p, p->rho, p->pressure_bar);
+
   /* Update variables. */
   p->force.f = grad_h_term;
   p->force.soundspeed = soundspeed;
   p->force.balsara = balsara;
+  p->force.pressure_bar_with_floor = comoving_pressure_with_floor;
 }
 
 /**
@@ -755,6 +766,11 @@ __attribute__((always_inline)) INLINE static void hydro_predict_extra(
   const float soundspeed = hydro_get_comoving_soundspeed(p);
 
   p->force.soundspeed = soundspeed;
+
+  /* update the required variables */
+  const float comoving_pressure_with_floor =
+      pressure_floor_get_pressure(p, p->rho, p->pressure_bar);
+  p->force.pressure_bar_with_floor = comoving_pressure_with_floor;
 }
 
 /**

src/hydro/PressureEnergy/hydro_iact.h

@@ -259,11 +259,18 @@ __attribute__((always_inline)) INLINE static void runner_iact_force(
   /* Convolve with the kernel */
   const float visc_acc_term = 0.5f * visc * (wi_dr + wj_dr) * r_inv;
 
+  /* Compute the ratio of pressures */
+  const float pressure_inverse_i =
+      pi->force.pressure_bar_with_floor / (pi->pressure_bar * pi->pressure_bar);
+  const float pressure_inverse_j =
+      pj->force.pressure_bar_with_floor / (pj->pressure_bar * pj->pressure_bar);
+
   /* SPH acceleration term */
-  const float sph_acc_term =
-      pj->u * pi->u * hydro_gamma_minus_one * hydro_gamma_minus_one *
-      ((f_ij / pi->pressure_bar) * wi_dr + (f_ji / pj->pressure_bar) * wj_dr) *
-      r_inv;
+  const float sph_acc_term = pj->u * pi->u * hydro_gamma_minus_one *
+                             hydro_gamma_minus_one *
+                             ((f_ij * pressure_inverse_i) * wi_dr +
+                              (f_ji * pressure_inverse_j) * wj_dr) *
+                             r_inv;
 
   /* Assemble the acceleration */
   const float acc = sph_acc_term + visc_acc_term;
@@ -278,11 +285,13 @@ __attribute__((always_inline)) INLINE static void runner_iact_force(
   pj->a_hydro[2] += mi * acc * dx[2];
 
   /* Get the time derivative for u. */
+
   const float sph_du_term_i = hydro_gamma_minus_one * hydro_gamma_minus_one *
-                              pj->u * pi->u * (f_ij / pi->pressure_bar) *
+                              pj->u * pi->u * (f_ij * pressure_inverse_i) *
                               wi_dr * dvdr * r_inv;
+
   const float sph_du_term_j = hydro_gamma_minus_one * hydro_gamma_minus_one *
-                              pi->u * pj->u * (f_ji / pj->pressure_bar) *
+                              pi->u * pj->u * (f_ji * pressure_inverse_j) *
                               wj_dr * dvdr * r_inv;
 
   /* Viscosity term */
@@ -386,11 +395,18 @@ __attribute__((always_inline)) INLINE static void runner_iact_nonsym_force(
   /* Convolve with the kernel */
   const float visc_acc_term = 0.5f * visc * (wi_dr + wj_dr) * r_inv;
 
+  /* Compute the ratio of pressures */
+  const float pressure_inverse_i =
+      pi->force.pressure_bar_with_floor / (pi->pressure_bar * pi->pressure_bar);
+  const float pressure_inverse_j =
+      pj->force.pressure_bar_with_floor / (pj->pressure_bar * pj->pressure_bar);
+
   /* SPH acceleration term */
-  const float sph_acc_term =
-      pj->u * pi->u * hydro_gamma_minus_one * hydro_gamma_minus_one *
-      ((f_ij / pi->pressure_bar) * wi_dr + (f_ji / pj->pressure_bar) * wj_dr) *
-      r_inv;
+  const float sph_acc_term = pj->u * pi->u * hydro_gamma_minus_one *
+                             hydro_gamma_minus_one *
+                             ((f_ij * pressure_inverse_i) * wi_dr +
+                              (f_ji * pressure_inverse_j) * wj_dr) *
+                             r_inv;
 
   /* Assemble the acceleration */
   const float acc = sph_acc_term + visc_acc_term;
@@ -402,7 +418,7 @@ __attribute__((always_inline)) INLINE static void runner_iact_nonsym_force(
 
   /* Get the time derivative for u. */
   const float sph_du_term_i = hydro_gamma_minus_one * hydro_gamma_minus_one *
-                              pj->u * pi->u * (f_ij / pi->pressure_bar) *
+                              pj->u * pi->u * (f_ij * pressure_inverse_i) *
                               wi_dr * dvdr * r_inv;
 
   /* Viscosity term */

src/hydro/PressureEnergy/hydro_part.h

@@ -168,6 +168,9 @@ struct part {
 
       /*! Balsara switch */
       float balsara;
+
+      /*! Pressure term including the pressure floor */
+      float pressure_bar_with_floor;
     } force;
   };
 

src/hydro_properties.c

@@ -34,6 +34,7 @@
 #include "hydro.h"
 #include "kernel_hydro.h"
 #include "parser.h"
+#include "pressure_floor.h"
 #include "units.h"
 
 #define hydro_props_default_max_iterations 30
@@ -186,6 +187,9 @@ void hydro_props_print(const struct hydro_props *p) {
   /* Print equation of state first */
   eos_print(&eos);
 
+  /* Then the pressure floor */
+  pressure_floor_print(&pressure_floor_props);
+
   /* Now SPH */
   message("Hydrodynamic scheme: %s in %dD.", SPH_IMPLEMENTATION,
           (int)hydro_dimension);
@@ -238,6 +242,7 @@ void hydro_props_print(const struct hydro_props *p) {
 void hydro_props_print_snapshot(hid_t h_grpsph, const struct hydro_props *p) {
 
   eos_print_snapshot(h_grpsph, &eos);
+  pressure_floor_print_snapshot(h_grpsph);
 
   io_write_attribute_i(h_grpsph, "Dimension", (int)hydro_dimension);
   io_write_attribute_s(h_grpsph, "Scheme", SPH_IMPLEMENTATION);

src/pressure_floor.c

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Copyright (c) 2019 Loic Hausammann (loic.hausammann@epfl.ch)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+
+/* This object's header. */
+#include "pressure_floor.h"
+
+/* Pressure floor for the physics model. */
+struct pressure_floor_properties pressure_floor_props;

src/pressure_floor.h

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Copyright (c) 2019 Matthieu Schaller (schaller@strw.leidenuniv.nl)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+#ifndef SWIFT_PRESSURE_FLOOR_H
+#define SWIFT_PRESSURE_FLOOR_H
+
+/**
+ * @file src/pressure_floor.h
+ * @brief Branches between the different pressure floor models
+ */
+
+/* Config parameters. */
+#include "../config.h"
+
+/* Local includes */
+#include "common_io.h"
+#include "cosmology.h"
+#include "error.h"
+#include "inline.h"
+
+extern struct pressure_floor_properties pressure_floor_props;
+
+/* Check if pressure floor is implemented in hydro */
+#ifndef PRESSURE_FLOOR_NONE
+#if defined(GADGET2_SPH) || defined(HOPKINS_PU_SPH)
+/* Implemented */
+#else
+#error Pressure floor not implemented with this hydro scheme
+#endif
+
+#endif
+/* Import the right pressure floor definition */
+#if defined(PRESSURE_FLOOR_NONE)
+#include "./pressure_floor/none/pressure_floor.h"
+#elif defined(PRESSURE_FLOOR_GEAR)
+#include "./pressure_floor/GEAR/pressure_floor.h"
+#endif
+
+#endif /* SWIFT_PRESSURE_FLOOR_H */

src/pressure_floor/GEAR/pressure_floor.h

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Copyright (c) 2019 Matthieu Schaller (schaller@strw.leidenuniv.nl)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+#ifndef SWIFT_PRESSURE_FLOOR_GEAR_H
+#define SWIFT_PRESSURE_FLOOR_GEAR_H
+
+#include "adiabatic_index.h"
+#include "cosmology.h"
+#include "equation_of_state.h"
+#include "hydro_properties.h"
+#include "parser.h"
+#include "part.h"
+#include "units.h"
+
+/**
+ * @file src/pressure_floor/GEAR/pressure_floor.h
+ * @brief Pressure floor used in the GEAR model
+ */
+
+/**
+ * @brief Properties of the pressure floor in the GEAR model.
+ */
+struct pressure_floor_properties {
+
+  /*! Jeans factor */
+  float n_jeans;
+
+  /*! The constants in internal units (4 G N_jeans^(2/3) / PI) */
+  float constants;
+};
+
+/**
+ * @brief Compute the physical pressure floor of a given #part.
+ *
+ * Note that the particle is not updated!!
+ *
+ * The inputs can be either in physical or comoving coordinates (the output is
+ * in the same coordinates).
+ *
+ * @param p The #part.
+ * @param rho The physical or comoving density.
+ * @param pressure The physical or comoving pressure without any pressure floor.
+ *
+ * @return The physical or comoving pressure with the floor.
+ */