systems/sync_point_delete

• C

  View on GitHub

  #include <sync_point_delete.h>
  #include <stdio.h>
   
  typedef struct {
      double x, y;
  } Position, Velocity;
   
  void Move(ecs_iter_t *it) {
      Position *p = ecs_field(it, Position, 0);
      const Velocity *v = ecs_field(it, const Velocity, 1);
   
      for (int i = 0; i < it->count; i ++) {
          p[i].x += v[i].x;
          p[i].y += v[i].y;
      }
  }
   
  void DeleteEntity(ecs_iter_t *it) {
      const Position *p = ecs_field(it, Position, 0);
   
      for (int i = 0; i < it->count; i ++) {
          if (p[i].x >= 3) {
              ecs_entity_t e = it->entities[i];
              printf("Delete entity %s\n", ecs_get_name(it->stage, e));
              ecs_delete(it->stage, e);
          }
      }
  }
   
  void PrintPosition(ecs_iter_t *it) {
      const Position *p = ecs_field(it, const Position, 0);
   
      for (int i = 0; i < it->count; i ++) {
          printf("%s: {%f, %f}\n", ecs_get_name(it->stage, it->entities[i]),
              p[i].x, p[i].y);
      }
  }
   
  int main(int argc, char *argv[]) {
      ecs_world_t *ecs = ecs_init_w_args(argc, argv);
   
      // This example shows how to annotate systems that delete entities, in a way
      // that allows the scheduler to correctly insert sync points. See the
      // sync_point example for more details on sync points.
      //
      // While annotating a system for a delete operation follows the same 
      // design as other operations, one key difference is that a system often 
      // does not know which components a to be deleted entity has. This makes it
      // impossible to annotate the system in advance for specific components.
      //
      // To ensure the scheduler is still able to insert the correct sync points,
      // a system can use a wildcard to indicate that any component could be
      // modified by the system, which forces the scheduler to insert a sync.
   
      ECS_COMPONENT(ecs, Position);
      ECS_COMPONENT(ecs, Velocity);
   
      // Basic move system.
      ECS_SYSTEM(ecs, Move, EcsOnUpdate, Position, [in] Velocity);
   
      // Delete entities when p.x >= 3. Add wildcard annotation to indicate any
      // component could be written by the system. Position itself is added as 
      // const, since inside the system we're only reading it.
      //
      // Note how the system uses the same annotations as the sync_point example.
      ECS_SYSTEM(ecs, DeleteEntity, EcsOnUpdate, [in] Position, [out] *());
   
      // Print resulting Position
      ECS_SYSTEM(ecs, PrintPosition, EcsPostUpdate, [in] Position);
   
      // Create a few test entities for a Position, Velocity query
      ecs_entity_t e1 = ecs_entity(ecs, { .name = "e1" });
      ecs_set(ecs, e1, Position, {0, 0});
      ecs_set(ecs, e1, Velocity, {1, 2});
   
      ecs_entity_t e2 = ecs_entity(ecs, { .name = "e2" });
      ecs_set(ecs, e2, Position, {1, 2});
      ecs_set(ecs, e2, Velocity, {1, 2});
   
      // Run systems. Debug logging enables us to see the generated schedule
      ecs_log_set_level(1);
      while (ecs_progress(ecs, 0.0f)) {
          if (!ecs_count(ecs, Position)) {
              break;  // No more entities left with Position
          }
      }
      ecs_log_set_level(-1); // Restore so we don't get world cleanup logs
   
      // Output:
      //  info: pipeline rebuild:
      //  info: | schedule: threading: 0, staging: 1:
      //  info: | | system Move
      //  info: | | system DeleteEntity
      //  info: | | merge
      //  info: | schedule: threading: 0, staging: 1:
      //  info: | | system PrintPosition
      //  info: | | merge
      //  e1: {1, 2}
      //  e2: {2, 4}
      //  Delete entity e2
      //  e1: {2, 4}
      //  Delete entity e1
      //  info: system Move deactivated
      //  info: system DeleteEntity deactivated
      //  info: system PrintPosition deactivated
      //
      // Removing the wildcard annotation from the DeleteEntity system will
      // remove the first sync point.
      //
      // Note how after both entities are deleted, all three systems are 
      // deactivated. This happens when there are no matching entities for a
      // system. A deactivated system is not ran by the scheduler, which reduces
      // overhead.
      //
      // To create the same system with ecs_system_init, do:
      //  ecs_system_init(ecs, &(ecs_system_desc_t){
      //      .query.terms = {
      //          { 
      //              .id = ecs_id(Position), 
      //              .inout = EcsIn
      //          },
      //          { 
      //              .id = EcsWildcard, 
      //              .inout = EcsOut, 
      //              .src.id = EcsIsEntity 
      //          }
      //      },
      //      .entity = {
      //          .name = "DeleteEntity"
      //      },
      //      .phase = EcsOnUpdate,
      //      .callback = DeleteEntity
      //  });
   
      return ecs_fini(ecs);
  }

• C++

  View on GitHub

  #include <sync_point_delete.h>
  #include <iostream>
   
  struct Position { 
      double x, y;
  };
   
  struct Velocity { 
      double x, y;
  };
   
  int main(int, char *[]) {
      flecs::world ecs;
   
      // This example shows how to annotate systems that delete entities, in a way
      // that allows the scheduler to correctly insert sync points. See the
      // sync_point example for more details on sync points.
      //
      // While annotating a system for a delete operation follows the same 
      // design as other operations, one key difference is that a system often 
      // does not know which components a to be deleted entity has. This makes it
      // impossible to annotate the system in advance for specific components.
      //
      // To ensure the scheduler is still able to insert the correct sync points,
      // a system can use a wildcard to indicate that any component could be
      // modified by the system, which forces the scheduler to insert a sync.
   
      // Basic move system.
      ecs.system<Position, const Velocity>("Move")
          .each([](Position& p, const Velocity& v) {
              p.x += v.x;
              p.y += v.y;
          });
   
      // Delete entities when p.x >= 3. Add wildcard annotation to indicate any
      // component could be written by the system. Position itself is added as 
      // const, since inside the system we're only reading it.
      ecs.system<const Position>("DeleteEntity")
          .write(flecs::Wildcard)
          .each([](flecs::entity e, const Position& p) {
              if (p.x >= 3) {
                  std::cout << "Delete entity " << e.name() << "\n";
                  e.destruct();
              }
          });
   
      // Print resulting Position. Note that this system will never print entities
      // that have been deleted by the previous system.
      ecs.system<const Position>("PrintPosition")
          .each([](flecs::entity e, const Position& p) {
              std::cout << e.name() << ": {" << p.x << ", " << p.y << "}\n";
          });
   
      // Create a few test entities for a Position, Velocity query
      ecs.entity("e1")
          .set<Position>({0, 0})
          .set<Velocity>({1, 2});
   
      ecs.entity("e2")
          .set<Position>({1, 2})
          .set<Velocity>({1, 2});
   
      // Run systems. Debug logging enables us to see the generated schedule
      flecs::log::set_level(1);
      while (ecs.progress()) {
          if (!ecs.count<Position>()) {
              break; // No more entities left with Position
          }
      }
      flecs::log::set_level(-1); // Restore so we don't get world cleanup logs
   
      // Output:
      //  info: pipeline rebuild:
      //  info: | schedule: threading: 0, staging: 1:
      //  info: | | system Move
      //  info: | | system DeleteEntity
      //  info: | | merge
      //  info: | schedule: threading: 0, staging: 1:
      //  info: | | system PrintPosition
      //  info: | | merge
      //  e1: {1, 2}
      //  e2: {2, 4}
      //  Delete entity e2
      //  e1: {2, 4}
      //  Delete entity e1
      //  info: system Move deactivated
      //  info: system DeleteEntity deactivated
      //  info: system PrintPosition deactivated
      //
      // Removing the wildcard annotation from the DeleteEntity system will
      // remove the first sync point.
      //
      // Note how after both entities are deleted, all three systems are 
      // deactivated. This happens when there are no matching entities for a
      // system. A deactivated system is not ran by the scheduler, which reduces
      // overhead.
  }