Feat: Improve performances for add/remove (#26)

* feat: improve add/remove performances

The pool of entities ids (filled with deleted entities) allows to use a slice instead of a map to store entities & component register.
The names are not manager by Volt anymore, the common method would be to add a MetadataComponent to the tracked entities (if necessary to fetch by names)

* chore: remove profiling in volt_test

* chore: documentation of events & naming

Clean documentation, removing entities names in the API

* chore: update benchmark values

* chore: clean documentation

BREAKING CHANGE: the naming of entities is removed

Author: ragoune

README.md

@@ -17,8 +17,8 @@ There is many ways to write an ECS, and Volt is based on the Archetype paradigm.
 ## Knowledge
 ### Entity
 An entity is the end object in a game (e.g. a character). It is only defined by
-its identifier called EntityId. This identifier is randomly generated, its type uint64 avoiding to generate twice the same id.
-It is also required to set a name for each entity, only used to easily retrieve them when required.
+its identifier called EntityId. This identifier is generated, its type uint64 avoiding to generate twice the same id.
+When an entity is removed, this identifier can be used again for a new one.
 
 Looking at the benchmark, a scene can handle between 100.000 to 1.000.000 depending on your machine and the complexity of the project.
 But of course, the lower the better, as it will allow the project to run on slower computers.
@@ -82,14 +82,14 @@ volt.RegisterComponent[transformComponent](world, &ComponentConfig[transformComp
 ```
 - Create the entity
 ```go 
-entityId := world.CreateEntity("entityName")
+entityId := world.CreateEntity()
 ```
-**Important**: the entity name MUST be unique.
+**Important**: the entity will receive a unique identifier. When the entity is removed, this id can be used again and assigned to a new entity.
 
 - Add the component to the entity
 ```go 
-component := volt.ConfigureComponent[transformComponent](&scene.World, transformConfiguration{x: 1.0, y: 2.0, z: 3.0})
-volt.AddComponent(&scene.World, entity, component)
+component := volt.ConfigureComponent[transformComponent](&world, transformConfiguration{x: 1.0, y: 2.0, z: 3.0})
+volt.AddComponent(&world, entity, component)
 ```
 - Remove the component to the entity
 ```go
@@ -102,15 +102,6 @@ if err != nil {
 ```go
 world.RemoveEntity(entityId)
 ```
-## Searching for an entity
-- Knowing an entity by its name, you can get its identifier:
-```go
-entityId := world.SearchEntity("entityName")
-```
-- The reversed search is also possible, fetching its name by its idenfier:
-```go
-entityName := world.GetEntityName(entityId)
-```
 
 ## Queries
 The most powerful feature is the possibility to query entities with a given set of Components.
@@ -189,12 +180,71 @@ world.HasTag(TAG_STATIC_ID, entityId)
 world.RemoveTag(TAG_STATIC_ID, entityId)
 ```
 
+## Events
+The lifecycle (creation/deletion) of entities and components can trigger events.
+You can configure a callback function for each of these events, to execute your custom code:
+```go
+world := volt.CreateWorld(100)
+world.SetEntityAddedFn(func(entityId volt.EntityId) {
+    fmt.Println("A new entity has been created", entityId)
+})
+world.SetEntityRemovedFn(func(entityId volt.EntityId) {
+    fmt.Println("An entity has been deleted", entityId)
+})
+world.SetComponentAddedFn(func(entityId volt.EntityId, componentId volt.ComponentId) {
+    fmt.Println("The component", componentId, "is attached to the entity", entityId)
+})
+world.SetComponentRemovedFn(func(entityId volt.EntityId, componentId volt.ComponentId) {
+fmt.Println("The component", componentId, "is removed from the entity", entityId)
+})
+```
+
+## Naming entities
+Volt managed the naming of entities up to the version 1.6.0. For performances reasons, this feature is removed from the v1.7.0+.
+You now have to keep track of the names by yourself in your application:
+- Having a simple map[name string]volt.EntityId, you can react to the events and register these. Keep in mind that if your scene has a lot
+of entities, it will probably have a huge impact on the garbage collector.
+- Add a MetadataComponent. To fetch an entity by its name can be very slow, so you probably do not want to name all your entities. For example:
+```go
+const MetadataComponentId = 0
+
+type MetadataComponent struct {
+	Name string
+}
+
+func (MetadataComponent MetadataComponent) GetComponentId() volt.ComponentId {
+	return MetadataComponentId
+}
+volt.RegisterComponent[MetadataComponent](&world, &volt.ComponentConfig[MetadataComponent]{BuilderFn: func(component any, configuration any) {}})
+
+func GetEntityName(world *volt.World, entityId volt.EntityId) string {
+    if world.HasComponents(entityId, MetadataComponentId) {
+        metadata := volt.GetComponent[MetadataComponent](world, entityId)
+    
+        return metadata.Name
+    }
+    
+    return ""
+}
+
+func (scene *Scene) SearchEntity(name string) volt.EntityId {
+    q := volt.CreateQuery1[MetadataComponent](&world, volt.QueryConfiguration{})
+    for result := range q.Foreach(nil) {
+        if result.A.Name == name {
+            return result.EntityId
+        }
+    }
+    
+    return 0
+}
+```
+
 ## Benchmark
 Few ECS tools exist for Go. Arche and unitoftime/ecs are probably the most looked at, and the most optimized.
 In the benchmark folder, this module is compared to both of them.
 
-- Go - v1.24.0
-- Volt - v1.5.0
+- Go - v1.25.3
+- Volt - v1.7.0
 - [Arche - v0.15.3](https://github.com/mlange-42/arche)
 - [UECS - v0.0.3](https://github.com/unitoftime/ecs)
 
@@ -207,19 +257,19 @@ cpu: AMD Ryzen 7 5800X 8-Core Processor
 
 | Benchmark                       | Iterations | ns/op     | B/op       | Allocs/op |
 |---------------------------------|------------|-----------|------------|-----------|
-| BenchmarkCreateEntityArche-16   | 171        | 6948273   | 11096966   | 61        |
-| BenchmarkIterateArche-16        | 2704       | 426795    | 354        | 4         |
-| BenchmarkAddArche-16            | 279        | 4250519   | 120089     | 100000    |
-| BenchmarkRemoveArche-16         | 249        | 4821120   | 100000     | 100000    |
-| BenchmarkCreateEntityUECS-16    | 34         | 37943381  | 49119549   | 200146    |
-| BenchmarkIterateUECS-16         | 3885       | 287027    | 128        | 3         |
-| BenchmarkAddUECS-16             | 30         | 38097927  | 4620476    | 100004    |
-| BenchmarkRemoveUECS-16          | 40         | 31008811  | 3302536    | 100000    |
-| BenchmarkCreateEntityVolt-16    | 49         | 27246822  | 41214216   | 200259    |
-| BenchmarkIterateVolt-16         | 3651       | 329858    | 264        | 9         |
-| BenchmarkIterateConcurrentlyVolt-16 | 10000      | 102732    | 3330       | 93        |
-| BenchmarkAddVolt-16             | 54         | 22508281  | 4597363    | 300001    |
-| BenchmarkRemoveVolt-16          | 72         | 17219355  | 400001     | 100000    |
+| BenchmarkCreateEntityArche-16   | 171        | 7138387   | 11096954   | 61        |
+| BenchmarkIterateArche-16        | 2798       | 429744    | 354        | 4         |
+| BenchmarkAddArche-16            | 253        | 4673362   | 122153     | 100000    |
+| BenchmarkRemoveArche-16         | 247        | 4840772   | 100000     | 100000    |
+| BenchmarkCreateEntityUECS-16    | 27         | 38852089  | 49119503   | 200146    |
+| BenchmarkIterateUECS-16         | 4892       | 235333    | 128        | 3         |
+| BenchmarkAddUECS-16             | 28         | 38982533  | 4721942    | 100005    |
+| BenchmarkRemoveUECS-16          | 30         | 40290316  | 3336712    | 100000    |
+| BenchmarkCreateEntityVolt-16    | 63         | 18836136  | 35181458   | 100101    |
+| BenchmarkIterateVolt-16         | 3619       | 337764    | 256        | 8         |
+| BenchmarkIterateConcurrentlyVolt-16 | 9164      | 121653    | 3324       | 91        |
+| BenchmarkAddVolt-16             | 103         | 11379690  | 4313182    | 300000    |
+| BenchmarkRemoveVolt-16          | 146         | 7647252  | 400001     | 100000    |
 
 These results show a few things:
 - Arche is the fastest tool for writes operations. In our game development though we would rather lean towards fastest read operations, because the games loops will read way more often than write.
@@ -236,8 +286,6 @@ The creator and maintainer of Arche has published more complex benchmarks availa
 https://github.com/mlange-42/go-ecs-benchmarks
 
 ## What is to come next ?
-- Tags (zero sized types) are useful to query entities with specific features: for example, in a renderer, to get only the entities with the boolean isCulled == false.
-This would hugely reduce the loops operations in some scenarios. Currently we can use the filters on the iterators, but it does not avoid the fact that every entity (with the given components) is looped by the renderer.
 - For now the system is not designed to manage writes on a concurrent way: it means it is not safe to add/remove components in queries 
   using multiples threads/goroutines. I need to figure out how to implement this, though I never met the need for this feature myself.
 

benchmark/volt_test.go

@@ -1,10 +1,10 @@
 package benchmark
 
 import (
-	"github.com/akmonengine/volt"
 	"math/rand/v2"
-	"strconv"
 	"testing"
+
+	"github.com/akmonengine/volt"
 )
 
 func BenchmarkCreateEntityVolt(b *testing.B) {
@@ -13,8 +13,8 @@ func BenchmarkCreateEntityVolt(b *testing.B) {
 		volt.RegisterComponent[testTransform](world, &volt.ComponentConfig[testTransform]{})
 		volt.RegisterComponent[testTag](world, &volt.ComponentConfig[testTag]{})
 
-		for j := range ENTITIES_COUNT {
-			volt.CreateEntityWithComponents2(world, strconv.Itoa(j),
+		for range ENTITIES_COUNT {
+			volt.CreateEntityWithComponents2(world,
 				testTransform{
 					x: rand.Float64() * 100,
 					y: rand.Float64() * 100,
@@ -34,7 +34,7 @@ func BenchmarkIterateVolt(b *testing.B) {
 	volt.RegisterComponent[testTag](world, &volt.ComponentConfig[testTag]{})
 
 	for i := 0; i < ENTITIES_COUNT; i++ {
-		id := world.CreateEntity(strconv.Itoa(i))
+		id := world.CreateEntity()
 		volt.AddComponent[testTransform](world, id, testTransform{})
 		volt.AddComponent[testTag](world, id, testTag{})
 	}
@@ -55,7 +55,7 @@ func BenchmarkIterateConcurrentlyVolt(b *testing.B) {
 	volt.RegisterComponent[testTag](world, &volt.ComponentConfig[testTag]{})
 
 	for i := 0; i < ENTITIES_COUNT; i++ {
-		id := world.CreateEntity(strconv.Itoa(i))
+		id := world.CreateEntity()
 		volt.AddComponent[testTransform](world, id, testTransform{})
 		volt.AddComponent[testTag](world, id, testTag{})
 	}
@@ -84,8 +84,8 @@ func BenchmarkAddVolt(b *testing.B) {
 	volt.RegisterComponent[testTag](world, &volt.ComponentConfig[testTag]{})
 
 	entities := make([]volt.EntityId, 0, ENTITIES_COUNT)
-	for j := range ENTITIES_COUNT {
-		entityId := world.CreateEntity(strconv.Itoa(j))
+	for range ENTITIES_COUNT {
+		entityId := world.CreateEntity()
 		volt.AddComponent(world, entityId, testTag{})
 		entities = append(entities, entityId)
 	}
@@ -113,8 +113,8 @@ func BenchmarkRemoveVolt(b *testing.B) {
 	volt.RegisterComponent[testTag](world, &volt.ComponentConfig[testTag]{})
 
 	entities := make([]volt.EntityId, 0, ENTITIES_COUNT)
-	for j := range ENTITIES_COUNT {
-		entityId := world.CreateEntity(strconv.Itoa(j))
+	for range ENTITIES_COUNT {
+		entityId := world.CreateEntity()
 		volt.AddComponent(world, entityId, testTag{})
 		entities = append(entities, entityId)
 	}

component.go

@@ -46,10 +46,10 @@ func ConfigureComponent[T ComponentInterface](world *World, conf any) T {
 //   - the entity has the component
 //   - an internal error occurs
 func AddComponent[T ComponentInterface](world *World, entityId EntityId, component T) error {
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return fmt.Errorf("entity %v does not exist", entityId)
 	}
+	entityRecord := world.entities[entityId]
 
 	componentId := component.GetComponentId()
 	if world.hasComponents(entityRecord, componentId) {
@@ -76,10 +76,10 @@ func AddComponent[T ComponentInterface](world *World, entityId EntityId, compone
 //
 // This solution is faster than an atomic solution.
 func AddComponents2[A, B ComponentInterface](world *World, entityId EntityId, a A, b B) error {
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return fmt.Errorf("entity %v does not exist", entityId)
 	}
+	entityRecord := world.entities[entityId]
 
 	return addComponents2(world, entityRecord, a, b)
 }
@@ -112,10 +112,10 @@ func addComponents2[A, B ComponentInterface](world *World, entityRecord entityRe
 //
 // This solution is faster than an atomic solution.
 func AddComponents3[A, B, C ComponentInterface](world *World, entityId EntityId, a A, b B, c C) error {
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return fmt.Errorf("entity %v does not exist", entityId)
 	}
+	entityRecord := world.entities[entityId]
 
 	return addComponents3(world, entityRecord, a, b, c)
 }
@@ -150,10 +150,10 @@ func addComponents3[A, B, C ComponentInterface](world *World, entityRecord entit
 //
 // This solution is faster than an atomic solution.
 func AddComponents4[A, B, C, D ComponentInterface](world *World, entityId EntityId, a A, b B, c C, d D) error {
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return fmt.Errorf("entity %v does not exist", entityId)
 	}
+	entityRecord := world.entities[entityId]
 
 	return addComponents4(world, entityRecord, a, b, c, d)
 }
@@ -189,10 +189,10 @@ func addComponents4[A, B, C, D ComponentInterface](world *World, entityRecord en
 //
 // This solution is faster than an atomic solution.
 func AddComponents5[A, B, C, D, E ComponentInterface](world *World, entityId EntityId, a A, b B, c C, d D, e E) error {
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return fmt.Errorf("entity %v does not exist", entityId)
 	}
+	entityRecord := world.entities[entityId]
 
 	return addComponents5(world, entityRecord, a, b, c, d, e)
 }
@@ -229,10 +229,10 @@ func addComponents5[A, B, C, D, E ComponentInterface](world *World, entityRecord
 //
 // This solution is faster than an atomic solution.
 func AddComponents6[A, B, C, D, E, F ComponentInterface](world *World, entityId EntityId, a A, b B, c C, d D, e E, f F) error {
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return fmt.Errorf("entity %v does not exist", entityId)
 	}
+	entityRecord := world.entities[entityId]
 
 	return addComponents6(world, entityRecord, a, b, c, d, e, f)
 }
@@ -270,10 +270,10 @@ func addComponents6[A, B, C, D, E, F ComponentInterface](world *World, entityRec
 //
 // This solution is faster than an atomic solution.
 func AddComponents7[A, B, C, D, E, F, G ComponentInterface](world *World, entityId EntityId, a A, b B, c C, d D, e E, f F, g G) error {
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return fmt.Errorf("entity %v does not exist", entityId)
 	}
+	entityRecord := world.entities[entityId]
 
 	return addComponents7(world, entityRecord, a, b, c, d, e, f, g)
 }
@@ -312,10 +312,10 @@ func addComponents7[A, B, C, D, E, F, G ComponentInterface](world *World, entity
 //
 // This solution is faster than an atomic solution.
 func AddComponents8[A, B, C, D, E, F, G, H ComponentInterface](world *World, entityId EntityId, a A, b B, c C, d D, e E, f F, g G, h H) error {
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return fmt.Errorf("entity %v does not exist", entityId)
 	}
+	entityRecord := world.entities[entityId]
 
 	return addComponents8(world, entityRecord, a, b, c, d, e, f, g, h)
 }
@@ -354,10 +354,10 @@ func addComponents8[A, B, C, D, E, F, G, H ComponentInterface](world *World, ent
 //   - the componentId is not registered in the World
 //   - an internal error occurs
 func (world *World) AddComponent(entityId EntityId, componentId ComponentId, conf any) error {
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return fmt.Errorf("entity %v does not exist", entityId)
 	}
+	entityRecord := world.entities[entityId]
 
 	if world.hasComponents(entityRecord, componentId) {
 		return fmt.Errorf("the entity %d already owns the component %d", entityId, componentId)
@@ -385,10 +385,10 @@ func (world *World) AddComponent(entityId EntityId, componentId ComponentId, con
 //   - the componentsIds are not registered in the World
 //   - an internal error occurs
 func (world *World) AddComponents(entityId EntityId, componentsIdsConfs ...ComponentIdConf) error {
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return fmt.Errorf("entity %v does not exist", entityId)
 	}
+	entityRecord := world.entities[entityId]
 
 	var componentsIds []ComponentId
 	for _, componentIdConf := range componentsIdsConfs {
@@ -423,10 +423,10 @@ func RemoveComponent[T ComponentInterface](world *World, entityId EntityId) erro
 	var t T
 	componentId := t.GetComponentId()
 
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return fmt.Errorf("entity %v does not exist", entityId)
 	}
+	entityRecord := world.entities[entityId]
 
 	if !world.hasComponents(entityRecord, componentId) {
 		return fmt.Errorf("the entity %d doesn't own the component %d", entityId, componentId)
@@ -486,10 +486,10 @@ func removeComponent(world *World, s storage, entityRecord entityRecord, compone
 //
 // It returns false if at least one ComponentId is not owned.
 func (world *World) HasComponents(entityId EntityId, componentsIds ...ComponentId) bool {
-	entityRecord, ok := world.entities[entityId]
-	if !ok {
+	if int(entityId) >= len(world.entities) {
 		return false
 	}
+	entityRecord := world.entities[entityId]
 
 	return world.hasComponents(entityRecord, componentsIds...)
 }