Merge branch 'logger_api1' into 'master'

Implement logger writer

See merge request !1104

configure.ac

@@ -1129,6 +1129,7 @@ if test "x$with_python" != "xno"; then
       AC_MSG_RESULT([$PYTHON_INCS])
   ])
   have_python="yes"
+  AC_DEFINE([HAVE_PYTHON],1,[Python appears to be present.])
 fi
 AC_SUBST([PYTHON_INCS])
 AM_CONDITIONAL([HAVEPYTHON],[test -n "$PYTHON_INCS"])

examples/main.c

@@ -1362,7 +1362,7 @@ int main(int argc, char *argv[]) {
     /* Write the state of the system before starting time integration. */
 #ifdef WITH_LOGGER
     if (e.policy & engine_policy_logger) {
-      logger_log_all(e.logger, &e);
+      logger_log_all_particles(e.logger, &e);
       engine_dump_index(&e);
     }
 #endif
@@ -1568,7 +1568,7 @@ int main(int argc, char *argv[]) {
     }
 #ifdef WITH_LOGGER
     if (e.policy & engine_policy_logger) {
-      logger_log_all(e.logger, &e);
+      logger_log_all_particles(e.logger, &e);
 
       /* Write a final index file */
       engine_dump_index(&e);

logger/logger_python_wrapper.c

@@ -22,6 +22,7 @@
 #include "logger_reader.h"
 #include "logger_time.h"
 
+#ifdef HAVE_PYTHON
 #define NPY_NO_DEPRECATED_API NPY_1_7_API_VERSION
 
 #include <Python.h>
@@ -447,3 +448,5 @@ PyMODINIT_FUNC PyInit_liblogger(void) {
 
   return m;
 }
+
+#endif // HAVE_PYTHON

logger/logger_tools.h

@@ -29,6 +29,7 @@
 #include "../src/error.h"
 #include "../src/inline.h"
 #include "../src/logger.h"
+#include "../src/logger_io.h"
 #include "../src/part_type.h"
 
 #ifdef HAVE_PYTHON

src/Makefile.am

@@ -135,7 +135,8 @@ nobase_noinst_HEADERS = align.h approx_math.h atomic.h barrier.h cycle.h error.h
 		 gravity/Potential/gravity.h gravity/Potential/gravity_iact.h gravity/Potential/gravity_io.h \
 		 gravity/Potential/gravity_debug.h gravity/Potential/gravity_part.h  \
 		 gravity/MultiSoftening/gravity.h gravity/MultiSoftening/gravity_iact.h gravity/MultiSoftening/gravity_io.h \
-		 gravity/MultiSoftening/gravity_debug.h gravity/MultiSoftening/gravity_part.h  \
+		 gravity/MultiSoftening/gravity_debug.h gravity/MultiSoftening/gravity_part.h \
+     gravity/MultiSoftening/gravity_logger.h \
 		 equation_of_state.h \
 		 equation_of_state/ideal_gas/equation_of_state.h equation_of_state/isothermal/equation_of_state.h \
 	 	 hydro.h hydro_io.h hydro_parameters.h \
@@ -147,7 +148,7 @@ nobase_noinst_HEADERS = align.h approx_math.h atomic.h barrier.h cycle.h error.h
 		 hydro/Default/hydro_parameters.h \
 		 hydro/Gadget2/hydro.h hydro/Gadget2/hydro_iact.h hydro/Gadget2/hydro_io.h \
                  hydro/Gadget2/hydro_debug.h hydro/Gadget2/hydro_part.h \
-		 hydro/Gadget2/hydro_parameters.h \
+     hydro/Gadget2/hydro_parameters.h hydro/Gadget2/hydro_logger.h \
 		 hydro/PressureEntropy/hydro.h hydro/PressureEntropy/hydro_iact.h hydro/PressureEntropy/hydro_io.h \
                  hydro/PressureEntropy/hydro_debug.h hydro/PressureEntropy/hydro_part.h \
 		 hydro/PressureEntropy/hydro_parameters.h \
@@ -209,7 +210,7 @@ nobase_noinst_HEADERS = align.h approx_math.h atomic.h barrier.h cycle.h error.h
                  riemann/riemann_checks.h \
 	 	 stars.h stars_io.h \
 		 stars/Default/stars.h stars/Default/stars_iact.h stars/Default/stars_io.h \
-		 stars/Default/stars_debug.h stars/Default/stars_part.h  \
+     stars/Default/stars_debug.h stars/Default/stars_part.h stars/Default/stars_logger.h  \
 		 stars/EAGLE/stars.h stars/EAGLE/stars_iact.h stars/EAGLE/stars_io.h \
 		 stars/EAGLE/stars_debug.h stars/EAGLE/stars_part.h \
 		 stars/GEAR/stars.h stars/GEAR/stars_iact.h stars/GEAR/stars_io.h \
@@ -293,7 +294,7 @@ nobase_noinst_HEADERS = align.h approx_math.h atomic.h barrier.h cycle.h error.h
 		 pressure_floor/GEAR/pressure_floor_iact.h pressure_floor/none/pressure_floor_iact.h \
 		 pressure_floor/GEAR/pressure_floor_struct.h pressure_floor/none/pressure_floor_struct.h \
 	         task_order/GEAR/task_order.h task_order/EAGLE/task_order.h task_order/default/task_order.h \
-		 sink/Default/sink.h sink/Default/sink_io.h sink/Default/sink_part.h \
+     sink/Default/sink.h sink/Default/sink_io.h sink/Default/sink_part.h \
 		 sink.h sink_io.h
 
 

src/cell.c

@@ -4883,6 +4883,15 @@ void cell_drift_part(struct cell *c, const struct engine *e, int force) {
            * by another thread before we do the deed. */
           if (!part_is_inhibited(p, e)) {
 
+#ifdef WITH_LOGGER
+            if (e->policy & engine_policy_logger) {
+              /* Log the particle one last time. */
+              logger_log_part(
+                  e->logger, p, xp, e, /* log_all */ 1,
+                  logger_pack_flags_and_data(logger_flag_delete, 0));
+            }
+#endif
+
             /* One last action before death? */
             hydro_remove_part(p, xp);
 
@@ -5053,6 +5062,17 @@ void cell_drift_gpart(struct cell *c, const struct engine *e, int force) {
 
             /* Remove the particle entirely */
             if (gp->type == swift_type_dark_matter) {
+
+#ifdef WITH_LOGGER
+              if (e->policy & engine_policy_logger) {
+                /* Log the particle one last time. */
+                logger_log_gpart(
+                    e->logger, gp, e, /* log_all */ 1,
+                    logger_pack_flags_and_data(logger_flag_delete, 0));
+              }
+#endif
+
+              /* Remove the particle */
               cell_remove_gpart(e, c, gp);
             }
           }
@@ -5194,6 +5214,15 @@ void cell_drift_spart(struct cell *c, const struct engine *e, int force) {
            * by another thread before we do the deed. */
           if (!spart_is_inhibited(sp, e)) {
 
+#ifdef WITH_LOGGER
+            if (e->policy & engine_policy_logger) {
+              /* Log the particle one last time. */
+              logger_log_spart(
+                  e->logger, sp, e, /* log_all */ 1,
+                  logger_pack_flags_and_data(logger_flag_delete, 0));
+            }
+#endif
+
             /* Remove the particle entirely */
             cell_remove_spart(e, c, sp);
           }
@@ -5365,6 +5394,12 @@ void cell_drift_bpart(struct cell *c, const struct engine *e, int force) {
            * by another thread before we do the deed. */
           if (!bpart_is_inhibited(bp, e)) {
 
+#ifdef WITH_LOGGER
+            if (e->policy & engine_policy_logger) {
+              error("Logging of black hole particles is not yet implemented.");
+            }
+#endif
+
             /* Remove the particle entirely */
             cell_remove_bpart(e, c, bp);
           }

src/engine.c

@@ -562,14 +562,11 @@ void engine_exchange_strays(struct engine *e, const size_t offset_parts,
 
 #ifdef WITH_LOGGER
     if (e->policy & engine_policy_logger) {
-      const uint32_t logger_flag =
-          logger_pack_flags_and_data(logger_flag_mpi_exit, node_id);
-
       /* Log the particle when leaving a rank. */
       logger_log_part(
           e->logger, &s->parts[offset_parts + k], &s->xparts[offset_parts + k],
-          logger_masks_all_part | logger_mask_data[logger_special_flags].mask,
-          logger_flag);
+          e, /* log_all_fields */ 1,
+          logger_pack_flags_and_data(logger_flag_mpi_exit, node_id));
     }
 #endif
   }
@@ -610,14 +607,11 @@ void engine_exchange_strays(struct engine *e, const size_t offset_parts,
 
 #ifdef WITH_LOGGER
     if (e->policy & engine_policy_logger) {
-      const uint32_t logger_flag =
-          logger_pack_flags_and_data(logger_flag_mpi_exit, node_id);
-
       /* Log the particle when leaving a rank. */
       logger_log_spart(
-          e->logger, &s->sparts[offset_sparts + k],
-          logger_masks_all_spart | logger_mask_data[logger_special_flags].mask,
-          logger_flag);
+          e->logger, &s->sparts[offset_sparts + k], e,
+          /* log_all_fields */ 1,
+          logger_pack_flags_and_data(logger_flag_mpi_exit, node_id));
     }
 #endif
   }
@@ -696,14 +690,11 @@ void engine_exchange_strays(struct engine *e, const size_t offset_parts,
     if ((e->policy & engine_policy_logger) &&
         s->gparts[offset_gparts + k].type == swift_type_dark_matter) {
 
-      const uint32_t logger_flag =
-          logger_pack_flags_and_data(logger_flag_mpi_exit, node_id);
-
       /* Log the particle when leaving a rank. */
       logger_log_gpart(
-          e->logger, &s->gparts[offset_gparts + k],
-          logger_masks_all_gpart | logger_mask_data[logger_special_flags].mask,
-          logger_flag);
+          e->logger, &s->gparts[offset_gparts + k], e,
+          /* log_all_fields */ 1,
+          logger_pack_flags_and_data(logger_flag_mpi_exit, node_id));
     }
 #endif
   }
@@ -937,22 +928,16 @@ void engine_exchange_strays(struct engine *e, const size_t offset_parts,
         struct gpart *gparts = &s->gparts[offset_gparts + count_gparts];
 
         /* Log the gas particles */
-        logger_log_parts(
-            e->logger, parts, xparts, prox->nr_parts_in,
-            logger_masks_all_part | logger_mask_data[logger_special_flags].mask,
-            flag);
+        logger_log_parts(e->logger, parts, xparts, prox->nr_parts_in, e,
+                         /* log_all_fields */ 1, flag);
 
         /* Log the stellar particles */
-        logger_log_sparts(e->logger, sparts, prox->nr_sparts_in,
-                          logger_masks_all_spart |
-                              logger_mask_data[logger_special_flags].mask,
-                          flag);
+        logger_log_sparts(e->logger, sparts, prox->nr_sparts_in, e,
+                          /* log_all_fields */ 1, flag);
 
         /* Log the gparts */
-        logger_log_gparts(e->logger, gparts, prox->nr_gparts_in,
-                          logger_masks_all_gpart |
-                              logger_mask_data[logger_special_flags].mask,
-                          flag);
+        logger_log_gparts(e->logger, gparts, prox->nr_gparts_in, e,
+                          /* log_all_fields */ 1, flag);
 
         /* Log the bparts */
         if (prox->nr_bparts_in > 0) {
@@ -3980,7 +3965,7 @@ void engine_init(struct engine *e, struct space *s, struct swift_params *params,
 #if defined(WITH_LOGGER)
   if (e->policy & engine_policy_logger) {
     e->logger = (struct logger_writer *)malloc(sizeof(struct logger_writer));
-    logger_init(e->logger, params);
+    logger_init(e->logger, e, params);
   }
 #endif
 

src/engine_redistribute.c

@@ -1004,22 +1004,16 @@ void engine_redistribute(struct engine *e) {
       const uint32_t flag = logger_pack_flags_and_data(logger_flag_mpi_exit, i);
 
       /* Log the hydro parts. */
-      logger_log_parts(
-          e->logger, &parts[part_offset], &xparts[part_offset], counts[c_ind],
-          logger_masks_all_part | logger_mask_data[logger_special_flags].mask,
-          flag);
+      logger_log_parts(e->logger, &parts[part_offset], &xparts[part_offset],
+                       counts[c_ind], e, /* log_all_fields */ 1, flag);
 
       /* Log the stellar parts. */
-      logger_log_sparts(
-          e->logger, &sparts[spart_offset], s_counts[c_ind],
-          logger_masks_all_spart | logger_mask_data[logger_special_flags].mask,
-          flag);
+      logger_log_sparts(e->logger, &sparts[spart_offset], s_counts[c_ind], e,
+                        /* log_all_fields */ 1, flag);
 
       /* Log the gparts */
-      logger_log_gparts(
-          e->logger, &gparts[gpart_offset], g_counts[c_ind],
-          logger_masks_all_gpart | logger_mask_data[logger_special_flags].mask,
-          flag);
+      logger_log_gparts(e->logger, &gparts[gpart_offset], g_counts[c_ind], e,
+                        /* log_all_fields */ 1, flag);
 
       /* Log the bparts */
       if (b_counts[c_ind] > 0) {
@@ -1110,23 +1104,17 @@ void engine_redistribute(struct engine *e) {
           logger_pack_flags_and_data(logger_flag_mpi_enter, i);
 
       /* Log the hydro parts. */
-      logger_log_parts(
-          e->logger, &s->parts[part_offset], &s->xparts[part_offset],
-          counts[c_ind],
-          logger_masks_all_part | logger_mask_data[logger_special_flags].mask,
-          flag);
+      logger_log_parts(e->logger, &s->parts[part_offset],
+                       &s->xparts[part_offset], counts[c_ind], e,
+                       /* log_all_fields */ 1, flag);
 
       /* Log the stellar parts. */
-      logger_log_sparts(
-          e->logger, &s->sparts[spart_offset], s_counts[c_ind],
-          logger_masks_all_spart | logger_mask_data[logger_special_flags].mask,
-          flag);
+      logger_log_sparts(e->logger, &s->sparts[spart_offset], s_counts[c_ind], e,
+                        /* log_all_fields */ 1, flag);
 
       /* Log the gparts */
-      logger_log_gparts(
-          e->logger, &s->gparts[gpart_offset], g_counts[c_ind],
-          logger_masks_all_gpart | logger_mask_data[logger_special_flags].mask,
-          flag);
+      logger_log_gparts(e->logger, &s->gparts[gpart_offset], g_counts[c_ind], e,
+                        /* log_all_fields */ 1, flag);
 
       /* Log the bparts */
       if (b_counts[c_ind] > 0) {

src/gravity/MultiSoftening/gravity_logger.h

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Coypright (c) 2020 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/>.
+ *
+ ******************************************************************************/
+#ifndef SWIFT_MULTISOFTENING_GRAVITY_LOGGER_H
+#define SWIFT_MULTISOFTENING_GRAVITY_LOGGER_H
+
+#include "logger_io.h"
+
+#ifdef WITH_LOGGER
+
+/*
+ * List of all possible mask.
+ * Outside the module, only logger_gravity_count is used.
+ */
+enum gravity_logger_fields {
+  gravity_logger_field_coordinates = 0,
+  gravity_logger_field_velocities,
+  gravity_logger_field_accelerations,
+  gravity_logger_field_masses,
+  gravity_logger_field_particle_ids,
+  gravity_logger_field_count,
+};
+
+/* Name of each possible mask. */
+static const char *gravity_logger_field_names[gravity_logger_field_count] = {
+    "Coordinates", "Velocities", "Accelerations", "Masses", "ParticleIDs",
+};
+
+/**
+ * @brief Initialize the logger.
+ *
+ * WARNING: this should be done in the same order than
+ * #gravity_logger_write_particle.
+ *
+ * @param mask_data Data for each type of mask.
+ *
+ * @return Number of masks used.
+ */
+INLINE static int gravity_logger_populate_mask_data(
+    struct mask_data *mask_data) {
+  mask_data[gravity_logger_field_coordinates] = logger_create_mask_entry(
+      gravity_logger_field_names[gravity_logger_field_coordinates],
+      3 * sizeof(double));
+
+  mask_data[gravity_logger_field_velocities] = logger_create_mask_entry(
+      gravity_logger_field_names[gravity_logger_field_velocities],
+      3 * sizeof(float));
+
+  mask_data[gravity_logger_field_accelerations] = logger_create_mask_entry(
+      gravity_logger_field_names[gravity_logger_field_accelerations],
+      3 * sizeof(float));
+
+  mask_data[gravity_logger_field_masses] = logger_create_mask_entry(
+      gravity_logger_field_names[gravity_logger_field_masses], sizeof(float));
+
+  mask_data[gravity_logger_field_particle_ids] = logger_create_mask_entry(
+      gravity_logger_field_names[gravity_logger_field_particle_ids],
+      sizeof(long long));
+
+  return gravity_logger_field_count;
+}
+
+/**
+ * @brief Generates the mask and compute the size of the record.
+ *
+ * @param masks The list of masks (same order than in #gravity_logger_init).
+ * @param part The #gpart that will be written.
+ * @param write_all Are we forcing to write all the fields?
+ *
+ * @param buffer_size (out) The requested size for the buffer.
+ * @param mask (out) The mask that will be written.
+ */
+INLINE static void gravity_logger_compute_size_and_mask(
+    const struct mask_data *masks, const struct gpart *part,
+    const int write_all, size_t *buffer_size, unsigned int *mask) {
+
+  /* Here you can decide your own writing logic */
+
+  /* Add the coordinates. */
+  *mask |= logger_add_field_to_mask(
+      masks[gravity_logger_field_coordinates],
+      gravity_logger_field_names[gravity_logger_field_coordinates],
+      buffer_size);
+
+  /* Add the velocities. */
+  *mask |= logger_add_field_to_mask(
+      masks[gravity_logger_field_velocities],
+      gravity_logger_field_names[gravity_logger_field_velocities], buffer_size);
+
+  /* Add the accelerations. */
+  *mask |= logger_add_field_to_mask(
+      masks[gravity_logger_field_accelerations],
+      gravity_logger_field_names[gravity_logger_field_accelerations],
+      buffer_size);
+
+  /* Add the masses. */
+  *mask |= logger_add_field_to_mask(
+      masks[gravity_logger_field_masses],
+      gravity_logger_field_names[gravity_logger_field_masses], buffer_size);
+
+  /* Add the ID. */
+  *mask |= logger_add_field_to_mask(
+      masks[gravity_logger_field_particle_ids],
+      gravity_logger_field_names[gravity_logger_field_particle_ids],
+      buffer_size);
+}
+
+/**
+ * @brief Write a particle to the logger.
+ *
+ * @param masks The list of masks (same order than in #gravity_logger_init).
+ * @param p The #gpart to write.
+ * @param mask The mask to use for this record.
+ * @param buff The buffer where to write the particle.
+ *
+ * @return The buffer after the data.
+ */
+INLINE static char *gravity_logger_write_particle(
+    const struct mask_data *mask_data, const struct gpart *p,
+    unsigned int *mask, char *buff) {
+
+  /* Write the coordinate. */
+  if (logger_should_write_field(
+          mask_data[gravity_logger_field_coordinates], mask,
+          gravity_logger_field_names[gravity_logger_field_coordinates])) {
+    memcpy(buff, p->x, 3 * sizeof(double));
+    buff += 3 * sizeof(double);
+  }
+
+  /* Write the velocity. */
+  if (logger_should_write_field(
+          mask_data[gravity_logger_field_velocities], mask,
+          gravity_logger_field_names[gravity_logger_field_velocities])) {
+    memcpy(buff, p->v_full, 3 * sizeof(float));
+    buff += 3 * sizeof(float);
+  }
+
+  /* Write the acceleration. */
+  if (logger_should_write_field(
+          mask_data[gravity_logger_field_accelerations], mask,
+          gravity_logger_field_names[gravity_logger_field_accelerations])) {
+    memcpy(buff, p->a_grav, 3 * sizeof(float));
+    buff += 3 * sizeof(float);
+  }
+
+  /* Write the mass. */
+  if (logger_should_write_field(
+          mask_data[gravity_logger_field_masses], mask,
+          gravity_logger_field_names[gravity_logger_field_masses])) {
+    memcpy(buff, &p->mass, sizeof(float));
+    buff += sizeof(float);
+  }
+
+  /* Write the Id. */
+  if (logger_should_write_field(
+          mask_data[gravity_logger_field_particle_ids], mask,
+          gravity_logger_field_names[gravity_logger_field_particle_ids])) {
+    memcpy(buff, &p->id_or_neg_offset, sizeof(long long));
+    buff += sizeof(long long);
+  }
+
+  return buff;
+}
+#endif  // WITH_LOGGER
+#endif  // SWIFT_MULTISOFTENING_GRAVITY_LOGGER_H

src/gravity_io.h

@@ -32,6 +32,7 @@
 #include "./gravity/Potential/gravity_io.h"
 #elif defined(MULTI_SOFTENING_GRAVITY)
 #include "./gravity/MultiSoftening/gravity_io.h"
+#include "./gravity/MultiSoftening/gravity_logger.h"
 #else
 #error "Invalid choice of gravity variant"
 #endif

src/hydro/Gadget2/hydro_logger.h

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Coypright (c) 2020 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/>.
+ *
+ ******************************************************************************/
+#ifndef SWIFT_GADGET2_HYDRO_LOGGER_H
+#define SWIFT_GADGET2_HYDRO_LOGGER_H
+
+#include "logger_io.h"
+
+#ifdef WITH_LOGGER
+
+/*
+ * List of all possible mask.
+ * Outside the module, only hydro_logger_field_count is used.
+ */
+enum hydro_logger_fields_mask {
+  hydro_logger_field_coordinates = 0,
+  hydro_logger_field_velocities,
+  hydro_logger_field_accelerations,
+  hydro_logger_field_masses,
+  hydro_logger_field_smoothing_lengths,
+  hydro_logger_field_entropies,
+  hydro_logger_field_particle_ids,
+  hydro_logger_field_densities,
+  hydro_logger_field_count,
+};
+
+/* Name of each possible mask. */
+static const char *hydro_logger_field_names[hydro_logger_field_count] = {
+    "Coordinates",      "Velocities", "Accelerations", "Masses",
+    "SmoothingLengths", "Entropies",  "ParticleIDs",   "Densities"};
+
+/**
+ * @brief Initialize the logger.
+ *
+ * WARNING: this should be done in the same order than
+ * #hydro_logger_write_particle.
+ *
+ * @param mask_data Data for each type of mask.
+ *
+ * @return Number of masks used.
+ */
+INLINE static int hydro_logger_populate_mask_data(struct mask_data *mask_data) {
+  mask_data[hydro_logger_field_coordinates] = logger_create_mask_entry(
+      hydro_logger_field_names[hydro_logger_field_coordinates],
+      3 * sizeof(double));
+
+  mask_data[hydro_logger_field_velocities] = logger_create_mask_entry(
+      hydro_logger_field_names[hydro_logger_field_velocities],
+      3 * sizeof(float));
+
+  mask_data[hydro_logger_field_accelerations] = logger_create_mask_entry(
+      hydro_logger_field_names[hydro_logger_field_accelerations],
+      3 * sizeof(float));
+
+  mask_data[hydro_logger_field_masses] = logger_create_mask_entry(
+      hydro_logger_field_names[hydro_logger_field_masses], sizeof(float));
+
+  mask_data[hydro_logger_field_smoothing_lengths] = logger_create_mask_entry(
+      hydro_logger_field_names[hydro_logger_field_smoothing_lengths],
+      sizeof(float));
+
+  mask_data[hydro_logger_field_entropies] = logger_create_mask_entry(
+      hydro_logger_field_names[hydro_logger_field_entropies], sizeof(float));
+
+  mask_data[hydro_logger_field_particle_ids] = logger_create_mask_entry(
+      hydro_logger_field_names[hydro_logger_field_particle_ids],
+      sizeof(long long));
+
+  mask_data[hydro_logger_field_densities] = logger_create_mask_entry(
+      hydro_logger_field_names[hydro_logger_field_densities], sizeof(float));
+
+  return hydro_logger_field_count;
+}
+
+/**
+ * @brief Generates the mask and compute the size of the record.
+ *
+ * @param masks The list of masks (same order than in #hydro_logger_init).
+ * @param part The #part that will be written.
+ * @param xpart The #xpart that will be written.
+ * @param write_all Are we forcing to write all the fields?
+ *
+ * @param buffer_size (out) The requested size for the buffer.
+ * @param mask (out) The mask that will be written.
+ */
+INLINE static void hydro_logger_compute_size_and_mask(
+    const struct mask_data *masks, const struct part *part,
+    const struct xpart *xpart, const int write_all, size_t *buffer_size,
+    unsigned int *mask) {
+
+  /* Here you can decide your own writing logic */
+
+  /* Add the coordinates. */
+  *mask |= logger_add_field_to_mask(
+      masks[hydro_logger_field_coordinates],
+      hydro_logger_field_names[hydro_logger_field_coordinates], buffer_size);
+
+  /* Add the velocities. */
+  *mask |= logger_add_field_to_mask(
+      masks[hydro_logger_field_velocities],
+      hydro_logger_field_names[hydro_logger_field_velocities], buffer_size);
+
+  /* Add the accelerations. */
+  *mask |= logger_add_field_to_mask(
+      masks[hydro_logger_field_accelerations],
+      hydro_logger_field_names[hydro_logger_field_accelerations], buffer_size);
+
+  /* Add the masses. */
+  *mask |= logger_add_field_to_mask(
+      masks[hydro_logger_field_masses],
+      hydro_logger_field_names[hydro_logger_field_masses], buffer_size);
+
+  /* Add the smoothing lengths. */
+  *mask |= logger_add_field_to_mask(