GEAR tracers

darwin-roduit · MatthieuSchaller · commit 46cf7dd9a202 · 2026-04-12T00:27:21.000+02:00
diff --git a/configure.ac b/configure.ac
@@ -2024,6 +2024,7 @@ case "$with_subgrid" in
    GEAR)
 	with_subgrid_cooling=grackle_0
 	with_subgrid_chemistry=GEAR_10
+	with_subgrid_tracers=GEAR
 	with_subgrid_pressure_floor=GEAR
 	with_subgrid_stars=GEAR
 	with_subgrid_star_formation=GEAR
@@ -2036,6 +2037,7 @@ case "$with_subgrid" in
    GEAR-G3)
 	with_subgrid_cooling=grackle_3
 	with_subgrid_chemistry=GEAR_10
+	with_subgrid_tracers=GEAR
 	with_subgrid_pressure_floor=none
 	with_subgrid_stars=GEAR
 	with_subgrid_star_formation=GEAR
@@ -2689,7 +2691,7 @@ fi
 #  Particle tracers
 AC_ARG_WITH([tracers],
    [AS_HELP_STRING([--with-tracers=<function>],
-      [chemistry function @<:@none, EAGLE default: none@:>@]
+      [chemistry function @<:@none, EAGLE, GEAR default: none@:>@]
    )],
    [with_tracers="$withval"],
    [with_tracers="none"]
@@ -2710,6 +2712,9 @@ case "$with_tracers" in
    EAGLE)
       AC_DEFINE([TRACERS_EAGLE], [1], [Tracers taken from the EAGLE model])
    ;;
+   GEAR)
+      AC_DEFINE([TRACERS_GEAR], [1], [Tracers taken from the GEAR model])
+   ;;
    *)
       AC_MSG_ERROR([Unknown tracers choice: $with_tracers])
    ;;
diff --git a/doc/RTD/source/SubgridModels/GEAR/dev_notes.rst b/doc/RTD/source/SubgridModels/GEAR/dev_notes.rst
@@ -1,5 +1,5 @@
 .. GEAR sub-grid model
-   Darwin Roduit, 5h January 2025
+   Darwin Roduit, 5th January 2026
 
 .. _gear_dev_notes:
 
diff --git a/doc/RTD/source/SubgridModels/GEAR/index.rst b/doc/RTD/source/SubgridModels/GEAR/index.rst
@@ -18,5 +18,6 @@ This model can be selected with the configuration option ``--with-subgrid=GEAR``
    supernova_feedback
    sinks/index
    output
+   tracers
    dev_notes
 
diff --git a/doc/RTD/source/SubgridModels/GEAR/output.rst b/doc/RTD/source/SubgridModels/GEAR/output.rst
@@ -8,6 +8,7 @@ Snapshots ouputs
 
 Here, we provide a summary of the quantities written in the snapshots, in addition to positions, velocities, masses, smoothing lengths and particle IDs.
 
+The tracer outputs are summarised on the :ref:`gear_tracers` page.
 
 Sink particles
 ~~~~~~~~~~~~~~
@@ -38,8 +39,15 @@ Sink particles
 +---------------------------------------+---------------------------------------------+------------------------+---------------------------------------------------+
 | ``BirthTimes``                        | | Time when the sink was created            | [U_T]                  | | Only used in *non-cosmological* runs.           |
 +---------------------------------------+---------------------------------------------+------------------------+---------------------------------------------------+
-
-
+| ``BirthDensities``                    | | Physical densities at the time of birth   | [U_M U_L^{-3}]         | | Stored at birth time/redshift.                  |
++---------------------------------------+---------------------------------------------+------------------------+---------------------------------------------------+
+| ``BirthTemperatures``                 | | Temperatures at the time of birth         | [U_K]                  | | Stored at birth time/redshift.                  |
++---------------------------------------+---------------------------------------------+------------------------+---------------------------------------------------+
+| ``AccretionRates``                    | | Physical instantaneous accretion rates    | [U_M U_T^{-1}]         | | At the current step                             |
++---------------------------------------+---------------------------------------------+------------------------+---------------------------------------------------+
+| ``StarFormationRates``                | | Star formation rates of the particles     | [U_M U_T^{-1}]         | | If negative, stores last time/scale-factor      |
+|                                       |                                             |                        | | at which gas was star-forming.                  |
++---------------------------------------+---------------------------------------------+------------------------+---------------------------------------------------+
 
 Stars
 ~~~~~
diff --git a/doc/RTD/source/SubgridModels/GEAR/tracers.rst b/doc/RTD/source/SubgridModels/GEAR/tracers.rst
@@ -0,0 +1,28 @@
+.. GEAR sub-grid model
+   Darwin Roduit, 10th April 2026
+
+.. _gear_tracers:
+
+Particle tracers
+~~~~~~~~~~~~~~~~
+
+Over the course of the simulation, the gas, sink and star particles record some information about their evolution. These are updated for a given particle every time it is active. The GEAR tracers module is located in the directory ``src/tracers/GEAR/``. To enable GEAR tracers, add ``--with-tracers=GEAR`` to your configuration options.
+
+Currently, GEAR tracers are only implemented for sink particles.
+
+Sink tracers
+------------
+
+The tracers track the long-term evolution of the sinks' accretion rates and SFR between different time slices. These tracers are used to capture the high-frequency variability of the the accretion rate and SFR that might be lost between snapshots.
+
+The time slices are specified by ``Snapshots:recording_triggers_sink``. By default, the number of recording time slices is 3. You can change this value in ``src/tracers_triggers.h`` and then recompile the code. These outputs are arrays of length ``num_snapshot_triggers_sink``.
+
++---------------------------------------+---------------------------------------------+-----------------------------+---------------------------------------------------+
+| Name                                  | Description                                 | Units                       | Comments                                          |
++=======================================+=============================================+=============================+===================================================+
+| ``AveragedAccretionRates``            | | Accretion rates averaged over the         | [U_M U_T^{-1}]              | | Averaged over the period set by the             |
+|                                       | | snapshot trigger intervals                |                             | | first N snapshot triggers.                      |
++---------------------------------------+---------------------------------------------+-----------------------------+---------------------------------------------------+
+| ``AveragedStarFormationRates``        | | Star formation rates averaged over the    | [U_M U_T^{-1}]              | | Averaged over the period set by the             |
+|                                       | | snapshot trigger intervals                |                             | | first N snapshot triggers.                      |
++---------------------------------------+---------------------------------------------+-----------------------------+---------------------------------------------------+
diff --git a/examples/IsolatedGalaxy/IsolatedGalaxy_multi_component/GEAR/params.yml b/examples/IsolatedGalaxy/IsolatedGalaxy_multi_component/GEAR/params.yml
@@ -26,11 +26,12 @@ TimeIntegration:
 
 # Parameters governing the snapshots
 Snapshots:
-  subdir:              snap  # snapshot directory
-  basename:            snapshot # Common part of the name of output files
-  time_first:          0.    # Time of the first output (in internal units)
-  delta_time:          1e-2  # Time difference between consecutive outputs (in internal units)
+  subdir:              snap                      # snapshot directory
+  basename:            snapshot                  # Common part of the name of output files
+  time_first:          0.                        # Time of the first output (in internal units)
+  delta_time:          1e-2                      # Time difference between consecutive outputs (in internal units)
   compression:         4
+  recording_triggers_sink:   [1e-2, 1e-3, 1e-4]  # Recording starts 10M, 1M and 0.1M years before a snapshot
 
 # Parameters governing the conserved quantities statistics
 Statistics:
diff --git a/examples/IsolatedGalaxy/IsolatedGalaxy_sink/isolated_galaxy.yml b/examples/IsolatedGalaxy/IsolatedGalaxy_sink/isolated_galaxy.yml
@@ -25,14 +25,15 @@ TimeIntegration:
 
 # Parameters governing the snapshots
 Snapshots:
-  basename:   output      # Common part of the name of output files
-  time_first: 0.          # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
-  delta_time: 0.01        # Time difference between consecutive outputs (in internal units)
+  basename:   output                             # Common part of the name of output files
+  time_first: 0.                                 # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
+  delta_time: 0.01                               # Time difference between consecutive outputs (in internal units)
+  recording_triggers_sink:   [1e-2, 1e-3, 1e-4]  # Recording starts 10M, 1M and 0.1M years before a snapshot
 
 Scheduler:
-  cell_extra_gparts: 100       # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
-  cell_extra_sinks: 100       # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
-  cell_extra_sparts: 100       # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
+  cell_extra_gparts: 100                         # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
+  cell_extra_sinks: 100                          # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
+  cell_extra_sparts: 100                         # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
 
 # Parameters governing the conserved quantities statistics
 Statistics:
diff --git a/examples/SinkParticles/HomogeneousBox/params.yml b/examples/SinkParticles/HomogeneousBox/params.yml
@@ -32,7 +32,8 @@ Snapshots:
   subdir: snap
   basename:   snapshot                           # Common part of the name of output files
   time_first: 0.                                 # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
-  delta_time: 1e-3                               # Time difference between consecutive outputs (in internal units)
+  delta_time: 1e-2                               # Time difference between consecutive outputs (in internal units)
+  recording_triggers_sink:   [1e-2, 1e-3, 1e-4]  # Recording starts 10M, 1M and 0.1M years before a snapshot
 
 # Parameters governing the scheduler.
 Scheduler:
diff --git a/examples/SinkParticles/HomogeneousBox/params_debug.yml b/examples/SinkParticles/HomogeneousBox/params_debug.yml
@@ -29,6 +29,7 @@ Snapshots:
   basename:   snapshot                                 # Common part of the name of output files
   time_first: 0.                                       # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
   delta_time: 0.01                                     # Time difference between consecutive outputs (in internal units)
+  recording_triggers_sink:   [1e-2, 1e-3, 1e-4]        # Recording starts 10M, 1M and 0.1M years before a snapshot
 
 # Parameters governing the restarts
 Restarts:
diff --git a/examples/SinkParticles/HomogeneousBoxSinkParticles/params.yml b/examples/SinkParticles/HomogeneousBoxSinkParticles/params.yml
@@ -27,16 +27,17 @@ TimeIntegration:
 Snapshots:
   subdir: snap
   basename:   snapshot                           # Common part of the name of output files
-  time_first: 0.                                 #230 Myr # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
+  time_first: 0.                                 # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
   delta_time: 10e-3                              # Time difference between consecutive outputs (in internal units)
+  recording_triggers_sink:   [-1, -1, -1]        # No recording needed in this example
 
 Scheduler:
   cell_extra_gparts: 100                         # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
   cell_extra_sinks:  100                         # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
   cell_extra_sparts: 100                         # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
   max_top_level_cells: 3                         #
   dependency_graph_frequency: 1                  # (Optional) Dumping frequency of the dependency graph. By default, writes only at the first step.
-  mpi_message_limit:          4                  #Default: 4
+  mpi_message_limit:          4                  # Default: 4
   dependency_graph_cell:      0
   links_per_tasks:           35
 
diff --git a/examples/SinkParticles/PlummerSphere/params.yml b/examples/SinkParticles/PlummerSphere/params.yml
@@ -26,9 +26,10 @@ TimeIntegration:
 # Parameters governing the snapshots
 Snapshots:
   subdir: snap
-  basename:   snapshot      # Common part of the name of output files
-  time_first: 0.            # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
-  delta_time: 1e-3          # Time difference between consecutive outputs (in internal units)
+  basename:   snapshot                     # Common part of the name of output files
+  time_first: 0.                           # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
+  delta_time: 1e-3                         # Time difference between consecutive outputs (in internal units)
+  recording_triggers_sink:   [-1, -1, -1]  # No recording needed in this example
 
 Scheduler:
   cell_extra_gparts: 10000      # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
diff --git a/examples/SubgridTests/StellarWindBubble/params.yml b/examples/SubgridTests/StellarWindBubble/params.yml
@@ -16,9 +16,10 @@ TimeIntegration:
 # Parameters governing the snapshots
 Snapshots:
   subdir: snap
-  basename:   snapshot      # Common part of the name of output files
-  time_first: 0.0           # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
-  delta_time: 1e-4          # Time difference between consecutive outputs (in internal units)
+  basename:   snapshot                     # Common part of the name of output files
+  time_first: 0.0                          # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
+  delta_time: 1e-4                         # Time difference between consecutive outputs (in internal units)
+  recording_triggers_sink:   [-1, -1, -1]  # Not recording for this test
 
 Scheduler:
   cell_extra_gparts: 10      # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
diff --git a/examples/SubgridTests/StellarWindInjection/params.yml b/examples/SubgridTests/StellarWindInjection/params.yml
@@ -16,9 +16,10 @@ TimeIntegration:
 # Parameters governing the snapshots
 Snapshots:
   subdir: snap
-  basename:   snapshot      # Common part of the name of output files
-  time_first: 0.0           # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
-  delta_time: 1e-3          # Time difference between consecutive outputs (in internal units)
+  basename:   snapshot                     # Common part of the name of output files
+  time_first: 0.0                          # (Optional) Time of the first output if non-cosmological time-integration (in internal units)
+  delta_time: 1e-3                         # Time difference between consecutive outputs (in internal units)
+  recording_triggers_sink:   [-1, -1, -1]  # Not recording for this test
 
 Scheduler:
   cell_extra_gparts: 10      # (Optional) Number of spare sparts per top-level allocated at rebuild time for on-the-fly creation.
diff --git a/examples/parameter_example.yml b/examples/parameter_example.yml
@@ -198,10 +198,10 @@ Snapshots:
   select_output:       selectoutput.yml # (Optional) File containing information to select outputs with (see documentation in the "Output Selection" section)
   run_on_dump:         0 # (Optional) Run the dump_command each time that a snapshot is dumped?
   dump_command:        ./submit_velociraptor.sh # (Optional) Command to run each time that a snapshot is dumped.
-  recording_triggers_part:   [1e-3, 1e-2] # (Optional) Time before the snapshots where the trigger for gas particle tracers start (in internal units).
-  recording_triggers_spart:  [1e-3, 1e-2] # (Optional) Time before the snapshots where the trigger for star particle tracers start (in internal units).
-  recording_triggers_bpart:  [1e-3, 1e-2] # (Optional) Time before the snapshots where the trigger for BH particle tracers start (in internal units).
-  recording_triggers_sink:   [1e-3, 1e-2] # (Optional) Time before the snapshots where the trigger for sink particle tracers start (in internal units).
+  recording_triggers_part:   [1e-3, 1e-2]        # (Optional) Time before the snapshots where the trigger for gas particle tracers start (in internal units). A negative value disables the recording of the corresponding array index.
+  recording_triggers_spart:  [1e-3, 1e-2]        # (Optional) Time before the snapshots where the trigger for star particle tracers start (in internal units). A negative value disables the recording of the corresponding array index.
+  recording_triggers_bpart:  [1e-3, 1e-2]        # (Optional) Time before the snapshots where the trigger for BH particle tracers start (in internal units). A negative value disables the recording of the corresponding array index.
+  recording_triggers_sink:   [1e-2, 1e-3, 1e-4]  # (Optional) Time before the snapshots where the trigger for sink particle tracers start (in internal units). A negative value disables the recording of the corresponding array index.
 
 
 # Parameters governing the CSDS snapshot system
diff --git a/src/Makefile.am b/src/Makefile.am
@@ -468,6 +468,8 @@ nobase_noinst_HEADERS += tracers/none/tracers.h tracers/none/tracers_struct.h
 nobase_noinst_HEADERS += tracers/none/tracers_io.h tracers/none/tracers_debug.h
 nobase_noinst_HEADERS += tracers/EAGLE/tracers.h tracers/EAGLE/tracers_struct.h
 nobase_noinst_HEADERS += tracers/EAGLE/tracers_io.h tracers/EAGLE/tracers_debug.h
+nobase_noinst_HEADERS += tracers/GEAR/tracers.h tracers/GEAR/tracers_struct.h
+nobase_noinst_HEADERS += tracers/GEAR/tracers_io.h tracers/GEAR/tracers_debug.h
 nobase_noinst_HEADERS += extra_io/EAGLE/extra_io.h extra_io/EAGLE/extra.h
 nobase_noinst_HEADERS += feedback/none/feedback.h feedback/none/feedback_struct.h feedback/none/feedback_iact.h
 nobase_noinst_HEADERS += feedback/none/feedback_properties.h feedback/none/feedback.h
diff --git a/src/sink/GEAR/sink.h b/src/sink/GEAR/sink.h
@@ -1127,7 +1127,7 @@ INLINE static void sink_update_sink_properties_after_star_formation(
     /* Record the current time as an indicator of when this particle was last
        star-forming. */
     if (with_cosmology) {
-      sink->SFR = cosmo->a;
+      sink->SFR = -cosmo->a;
     } else {
       sink->SFR = -time;
     }
diff --git a/src/sink/GEAR/sink_part.h b/src/sink/GEAR/sink_part.h
@@ -21,6 +21,7 @@
 #define SWIFT_GEAR_SINK_PART_H
 
 #include "timeline.h"
+#include "tracers_struct.h"
 
 #define sink_need_unique_id 1
 
@@ -177,6 +178,9 @@ struct sink {
   /*! sink merger information (e.g. merging ID) */
   struct sink_sink_data merger_data;
 
+  /*! Tracer structure */
+  struct tracers_sink_data tracers_data;
+
 #ifdef SWIFT_DEBUG_CHECKS
 
   /* Time of the last drift */
diff --git a/src/tracers.h b/src/tracers.h
@@ -32,6 +32,8 @@
 #include "./tracers/none/tracers.h"
 #elif defined(TRACERS_EAGLE)
 #include "./tracers/EAGLE/tracers.h"
+#elif defined(TRACERS_GEAR)
+#include "./tracers/GEAR/tracers.h"
 #else
 #error "Invalid choice of tracers."
 #endif
diff --git a/src/tracers/GEAR/tracers.h b/src/tracers/GEAR/tracers.h
diff --git a/src/tracers/GEAR/tracers_debug.h b/src/tracers/GEAR/tracers_debug.h
diff --git a/src/tracers/GEAR/tracers_io.h b/src/tracers/GEAR/tracers_io.h
diff --git a/src/tracers/GEAR/tracers_struct.h b/src/tracers/GEAR/tracers_struct.h
diff --git a/src/tracers_debug.h b/src/tracers_debug.h
diff --git a/src/tracers_io.h b/src/tracers_io.h
diff --git a/src/tracers_struct.h b/src/tracers_struct.h
diff --git a/src/tracers_triggers.h b/src/tracers_triggers.h
