Moved the compiled-time parameters of the EAGLE black hole model to a separate file for clarity.

src/Makefile.am

@@ -235,7 +235,7 @@ nobase_noinst_HEADERS = align.h approx_math.h atomic.h barrier.h cycle.h error.h
                  black_holes/Default/black_holes_struct.h \
                  black_holes/EAGLE/black_holes.h black_holes/EAGLE/black_holes_io.h \
 		 black_holes/EAGLE/black_holes_part.h black_holes/EAGLE/black_holes_iact.h \
-                 black_holes/EAGLE/black_holes_properties.h \
+                 black_holes/EAGLE/black_holes_properties.h black_holes/EAGLE/black_holes_parameters.h \
                  black_holes/EAGLE/black_holes_struct.h \
 		 pressure_floor/GEAR/pressure_floor.h pressure_floor/none/pressure_floor.h \
 		 pressure_floor/GEAR/pressure_floor_iact.h pressure_floor/none/pressure_floor_iact.h \

src/black_holes/EAGLE/black_holes_iact.h

@@ -20,6 +20,7 @@
 #define SWIFT_EAGLE_BH_IACT_H
 
 /* Local includes */
+#include "black_holes_parameters.h"
 #include "gravity.h"
 #include "hydro.h"
 #include "random.h"
@@ -146,11 +147,13 @@ runner_iact_nonsym_bh_gas_swallow(const float r2, const float *dx,
 
   /* Start by checking the repositioning criteria */
 
-  /* Note the factor 9 is taken from EAGLE. Will be turned into a parameter */
+  /* (Square of) Max repositioning distance allowed based on the softening */
   const float max_dist_repos2 =
       kernel_gravity_softening_plummer_equivalent_inv *
-      kernel_gravity_softening_plummer_equivalent_inv * 9.f *
-      grav_props->epsilon_baryon_cur * grav_props->epsilon_baryon_cur;
+      kernel_gravity_softening_plummer_equivalent_inv *
+      const_max_repositioning_distance_ratio *
+      const_max_repositioning_distance_ratio * grav_props->epsilon_baryon_cur *
+      grav_props->epsilon_baryon_cur;
 
   /* This gas neighbour is close enough that we can consider it's potential
      for repositioning */
@@ -250,11 +253,13 @@ runner_iact_nonsym_bh_bh_swallow(const float r2, const float *dx,
 
   const float v2_pec = v2 * cosmo->a2_inv;
 
-  /* Note the factor 9 is taken from EAGLE. Will be turned into a parameter */
+  /* (Square of) Max repositioning distance allowed based on the softening */
   const float max_dist_repos2 =
       kernel_gravity_softening_plummer_equivalent_inv *
-      kernel_gravity_softening_plummer_equivalent_inv * 9.f *
-      grav_props->epsilon_baryon_cur * grav_props->epsilon_baryon_cur;
+      kernel_gravity_softening_plummer_equivalent_inv *
+      const_max_repositioning_distance_ratio *
+      const_max_repositioning_distance_ratio * grav_props->epsilon_baryon_cur *
+      grav_props->epsilon_baryon_cur;
 
   /* This gas neighbour is close enough that we can consider it's potential
      for repositioning */
@@ -285,10 +290,11 @@ runner_iact_nonsym_bh_bh_swallow(const float r2, const float *dx,
     h = hj;
   }
 
-  /* Note the factor 9 is taken from EAGLE. Will be turned into a parameter */
+  /* (Square of) Max swallowing distance allowed based on the softening */
   const float max_dist_merge2 =
       kernel_gravity_softening_plummer_equivalent_inv *
-      kernel_gravity_softening_plummer_equivalent_inv * 9.f *
+      kernel_gravity_softening_plummer_equivalent_inv *
+      const_max_merging_distance_ratio * const_max_merging_distance_ratio *
       grav_props->epsilon_baryon_cur * grav_props->epsilon_baryon_cur;
 
   const float G_Newton = grav_props->G_Newton;

src/black_holes/EAGLE/black_holes_parameters.h

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Coypright (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_EAGLE_BLACK_HOLES_PARAMETERS_H
+#define SWIFT_EAGLE_BLACK_HOLES_PARAMETERS_H
+
+/* Configuration file */
+#include "config.h"
+
+/**
+ * @file EAGLE/black_holes_parameters.h
+ * @brief Parameters of the EAGLE black holes
+ *        model that need to be defined at compile time.
+ */
+
+/*! Maximal distance for merging particles in units of the (spline not Plummer)
+ *  softening length. */
+#define const_max_merging_distance_ratio 3.f
+
+/*! Maximal distance for repositioning particles in units of the (spline not
+ * Plummer) softening length. */
+#define const_max_repositioning_distance_ratio 3.f
+
+#endif /* SWIFT_EAGLE_BLACK_HOLES_PARAMETERS_H */