Randomize time value for systems with interval to reduce spiking behavior

Author: SanderMertens

flecs.c

@@ -35945,7 +35945,8 @@ ecs_entity_t ecs_set_interval(
 
     timer = ecs_set(world, timer, EcsTimer, {
         .timeout = interval,
-        .active = true
+        .active = true,
+        .time = ((ecs_ftime_t)rand() / (ecs_ftime_t)RAND_MAX) * interval
     });
 
     ecs_system_t *system_data = ecs_poly_get(world, timer, ecs_system_t);

flecs.h

@@ -565,6 +565,8 @@ extern "C" {
 #pragma clang diagnostic ignored "-Wenum-constexpr-conversion"
 /* Very difficult to workaround this warning in C, especially for an ECS. */
 #pragma clang diagnostic ignored "-Wunsafe-buffer-usage"
+/* This warning gets thrown when trying to cast pointer returned from dlproc */
+#pragma clang diagnostic ignored "-Wcast-function-type-strict"
 #elif defined(ECS_TARGET_GNU)
 #ifndef __cplusplus
 #pragma GCC diagnostic ignored "-Wdeclaration-after-statement"

src/addons/timer.c

@@ -153,7 +153,8 @@ ecs_entity_t ecs_set_interval(
 
     timer = ecs_set(world, timer, EcsTimer, {
         .timeout = interval,
-        .active = true
+        .active = true,
+        .time = ((ecs_ftime_t)rand() / (ecs_ftime_t)RAND_MAX) * interval
     });
 
     ecs_system_t *system_data = ecs_poly_get(world, timer, ecs_system_t);

test/cpp_api/src/System.cpp

@@ -2043,6 +2043,9 @@ void System_interval_tick_source(void) {
 
     flecs::timer t = ecs.timer().interval(2.1);
 
+    flecs::Timer *timer = t.get_mut<flecs::Timer>();
+    timer->time = 0;
+
     int32_t sys_a_invoked = 0, sys_b_invoked = 0;
 
     ecs.system()

test/custom_builds/c/timer/src/main.c

@@ -28,6 +28,9 @@ int main(int argc, char *argv[]) {
     });
     assert(s != 0);
 
+    EcsTimer *timer = ecs_get_mut(world, s, EcsTimer);
+    timer->time = 0;
+
     ecs_entity_t e = ecs_new_id(world);
     ecs_set(world, e, Position, {10, 20});
     ecs_set(world, e, Velocity, {1, 2});

test/custom_builds/cpp/timer/src/main.cpp

@@ -12,13 +12,16 @@ struct Velocity {
 int main(int, char *[]) {
     flecs::world ecs;
 
-    ecs.system<Position, const Velocity>()
+    flecs::entity s = ecs.system<Position, const Velocity>()
         .interval(2.9f)
         .each([](Position& p, const Velocity& v) {
             p.x += v.x;
             p.y += v.y;
         });
 
+    flecs::Timer *t = s.get_mut<flecs::Timer>();
+    t->time = 0;
+
     auto e = ecs.entity()
         .set<Position>({10, 20})
         .set<Velocity>({1, 2});