Only do feedback for stars with an age > 0.

src/feedback/EAGLE/feedback.h

@@ -56,9 +56,6 @@ __attribute__((always_inline)) INLINE static void feedback_init_spart(
 __attribute__((always_inline)) INLINE static void feedback_first_init_spart(
     struct spart* sp, const struct feedback_props* feedback_props) {
 
-  sp->birth_density = -1.f;
-  sp->birth_time = feedback_props->spart_first_init_birth_time;
-
   feedback_init_spart(sp);
 }
 
@@ -74,8 +71,31 @@ __attribute__((always_inline)) INLINE static void feedback_first_init_spart(
 __attribute__((always_inline)) INLINE static void feedback_prepare_spart(
     struct spart* sp, const struct feedback_props* feedback_props) {
 
-  /* Zero all the output */
-  bzero(&sp->feedback_data, sizeof(struct feedback_spart_data));
+  /* Zero the amount of mass that is distributed */
+  sp->feedback_data.to_distribute.mass = 0.f;
+
+  /* Zero the number of SN */
+  sp->feedback_data.to_distribute.num_SNIa = 0.f;
+  sp->feedback_data.to_distribute.num_SNII = 0.f;
+  sp->feedback_data.to_distribute.num_SNe = 0.f;
+
+  /* Zero the enrichment quantities */
+  for (int i = 0; i < chemistry_element_count; i++)
+    sp->feedback_data.to_distribute.metal_mass[i] = 0.f;
+  sp->feedback_data.to_distribute.total_metal_mass = 0.f;
+  sp->feedback_data.to_distribute.mass_from_AGB = 0.f;
+  sp->feedback_data.to_distribute.metal_mass_from_AGB = 0.f;
+  sp->feedback_data.to_distribute.mass_from_SNII = 0.f;
+  sp->feedback_data.to_distribute.metal_mass_from_SNII = 0.f;
+  sp->feedback_data.to_distribute.mass_from_SNIa = 0.f;
+  sp->feedback_data.to_distribute.metal_mass_from_SNIa = 0.f;
+  sp->feedback_data.to_distribute.Fe_mass_from_SNIa = 0.f;
+
+  /* Zero the energy to inject */
+  sp->feedback_data.to_distribute.d_energy = 0.f;
+
+  /* Zero the feedback probability */
+  sp->feedback_data.to_distribute.heating_probability = 0.f;
 }
 
 /**
@@ -85,34 +105,22 @@ __attribute__((always_inline)) INLINE static void feedback_prepare_spart(
  * this information to a different MPI rank.
  *
  * @param sp The particle to act upon
+ * @param feedback_propss The #feedback_props structure.
  * @param cosmo The current cosmological model.
- * @param stars_properties The #stars_props
+ * @param us The unit system.
+ * @param star_age_beg_step The age of the star at the star of the time-step in
+ * internal units.
+ * @param dt The time-step size of this star in internal units.
  */
 __attribute__((always_inline)) INLINE static void feedback_evolve_spart(
     struct spart* restrict sp, const struct feedback_props* feedback_props,
     const struct cosmology* cosmo, const struct unit_system* us,
-    double star_age, double dt) {
-
-  /* Zero the number of SN and amount of mass that is distributed */
-  sp->feedback_data.to_distribute.num_SNIa = 0;
-  sp->feedback_data.to_distribute.num_SNII = 0;
-  sp->feedback_data.to_distribute.mass = 0;
-
-  /* Zero the enrichment quantities */
-  for (int i = 0; i < chemistry_element_count; i++)
-    sp->feedback_data.to_distribute.metal_mass[i] = 0;
-  sp->feedback_data.to_distribute.total_metal_mass = 0;
-  sp->feedback_data.to_distribute.mass_from_AGB = 0;
-  sp->feedback_data.to_distribute.metal_mass_from_AGB = 0;
-  sp->feedback_data.to_distribute.mass_from_SNII = 0;
-  sp->feedback_data.to_distribute.metal_mass_from_SNII = 0;
-  sp->feedback_data.to_distribute.mass_from_SNIa = 0;
-  sp->feedback_data.to_distribute.metal_mass_from_SNIa = 0;
-  sp->feedback_data.to_distribute.Fe_mass_from_SNIa = 0;
+    const double star_age_beg_step, const double dt) {
 
   /* Compute amount of enrichment and feedback that needs to be done in this
    * step */
-  compute_stellar_evolution(feedback_props, cosmo, sp, us, star_age, dt);
+  compute_stellar_evolution(feedback_props, cosmo, sp, us, star_age_beg_step,
+                            dt);
 
   /* Decrease star mass by amount of mass distributed to gas neighbours */
   sp->mass -= sp->feedback_data.to_distribute.mass;

src/feedback/EAGLE/feedback_properties.h

@@ -148,9 +148,6 @@ struct feedback_props {
 
   /* wind delay time for SNII */
   float SNII_wind_delay;
-
-  /* Value to set birth time of stars read from ICs */
-  float spart_first_init_birth_time;
 };
 
 void feedback_props_init(struct feedback_props *fp,

src/runner.c

@@ -205,19 +205,6 @@ void runner_do_stars_ghost(struct runner *r, struct cell *c, int timer) {
         /* Get a direct pointer on the part. */
         struct spart *sp = &sparts[sid[i]];
 
-        const integertime_t ti_step = get_integer_timestep(sp->time_bin);
-        const integertime_t ti_begin =
-            get_integer_time_begin(e->ti_current - 1, sp->time_bin);
-
-        /* Get particle time-step */
-        double dt;
-        if (with_cosmology) {
-          dt = cosmology_get_delta_time(e->cosmology, ti_begin,
-                                        ti_begin + ti_step);
-        } else {
-          dt = get_timestep(sp->time_bin, e->time_base);
-        }
-
 #ifdef SWIFT_DEBUG_CHECKS
         /* Is this part within the timestep? */
         if (!spart_is_active(sp, e))
@@ -375,17 +362,42 @@ void runner_do_stars_ghost(struct runner *r, struct cell *c, int timer) {
         /* Only do feedback if stars have a reasonable birth time */
         if (sp->birth_time != -1.) {
 
-          /* Calculate age of the star */
-          double star_age;
+          const integertime_t ti_step = get_integer_timestep(sp->time_bin);
+          const integertime_t ti_begin =
+              get_integer_time_begin(e->ti_current - 1, sp->time_bin);
+
+          /* Get particle time-step */
+          double dt;
           if (with_cosmology) {
-            star_age = cosmology_get_delta_time_from_scale_factors(
+            dt = cosmology_get_delta_time(e->cosmology, ti_begin,
+                                          ti_begin + ti_step);
+          } else {
+            dt = get_timestep(sp->time_bin, e->time_base);
+          }
+
+          /* Calculate age of the star at current time */
+          double star_age_end_of_step;
+          if (with_cosmology) {
+            star_age_end_of_step = cosmology_get_delta_time_from_scale_factors(
                 cosmo, sp->birth_scale_factor, (float)cosmo->a);
           } else {
-            star_age = e->time - sp->birth_time;
+            star_age_end_of_step = e->time - sp->birth_time;
           }
 
-          /* Compute the stellar evolution  */
-          feedback_evolve_spart(sp, feedback_props, cosmo, us, star_age, dt);
+          /* Reset the feedback fields of the star particle */
+          feedback_prepare_spart(sp, feedback_props);
+
+          /* Has this star been around for a while ? */
+          if (star_age_end_of_step > 0.) {
+
+            /* Age of the star at the start of the step */
+            const double star_age_beg_of_step =
+                max(star_age_end_of_step - dt, 0.);
+
+            /* Compute the stellar evolution  */
+            feedback_evolve_spart(sp, feedback_props, cosmo, us,
+                                  star_age_beg_of_step, dt);
+          }
         }
       }
 

src/stars/Default/stars_part.h

@@ -87,7 +87,7 @@ struct spart {
 
   /*! Feedback structure */
   struct feedback_spart_data feedback_data;
-  
+
   /*! Tracer structure */
   struct tracers_xpart_data tracers_data;
 

src/stars/EAGLE/stars.h

@@ -66,6 +66,9 @@ __attribute__((always_inline)) INLINE static void stars_first_init_spart(
 
   sp->time_bin = 0;
 
+  sp->birth_density = -1.f;
+  sp->birth_time = stars_properties->spart_first_init_birth_time;
+
   stars_init_spart(sp);
 }
 

src/stars/EAGLE/stars_io.h

@@ -131,6 +131,11 @@ INLINE static void stars_props_init(struct stars_props *sp,
     sp->log_max_h_change = p->log_max_h_change;
   else
     sp->log_max_h_change = logf(powf(max_volume_change, hydro_dimension_inv));
+
+  /* Read birth time to set all stars in ICs to (defaults to -1 to indicate star
+   * present in ICs) */
+  sp->spart_first_init_birth_time = parser_get_opt_param_float(
+      params, "EAGLEFeedback:birth_time_override", -1);
 }
 
 /**

src/stars/EAGLE/stars_part.h

@@ -156,6 +156,9 @@ struct stars_props {
 
   /*! Maximal change of h over one time-step */
   float log_max_h_change;
+
+  /*! Value to set birth time of stars read from ICs */
+  float spart_first_init_birth_time;
 };
 
 #endif /* SWIFT_EAGLE_STAR_PART_H */