From 4ada634130ea495a21d5d55e7e3e19d5e5650082 Mon Sep 17 00:00:00 2001
From: Christian Treffs <christian.treffs@7p-group.com>
Date: Tue, 31 Oct 2017 11:32:07 +0100
Subject: [PATCH] Fix sparse component set performance

---
 Sources/FirebladeECS/SparseSet.swift | 66 ++++++++++------------------
 1 file changed, 22 insertions(+), 44 deletions(-)

diff --git a/Sources/FirebladeECS/SparseSet.swift b/Sources/FirebladeECS/SparseSet.swift
index 0777144..8248e84 100644
--- a/Sources/FirebladeECS/SparseSet.swift
+++ b/Sources/FirebladeECS/SparseSet.swift
@@ -7,43 +7,34 @@
 
 public class SparseComponentSet {
 	public typealias Element = Component
-	public let chunkSize: Int = 4096
 	fileprivate typealias ComponentIdx = Int
 	fileprivate var size: Int = 0
-
-	fileprivate class Pair {
-		let key: EntityIndex
-		let value: Element
-		init(key: EntityIndex, value: Element) {
-			self.key = key
-			self.value = value
-		}
-	}
-
 	fileprivate var dense: ContiguousArray<Pair?>
 	fileprivate var sparse: [EntityIndex: ComponentIdx]
+	fileprivate typealias Pair = (key: EntityIndex, value: Element)
 
 	public init() {
 		dense = ContiguousArray<Pair?>()
-		dense.reserveCapacity(chunkSize)
-		sparse = [EntityIndex: ComponentIdx].init(minimumCapacity: chunkSize)
+		sparse = [EntityIndex: ComponentIdx]()
+	}
+
+	deinit {
+		clear()
 	}
 
 	public var count: Int { return size }
-	internal var capacitySparse: Int { return sparse.count }
-	internal var capacityDense: Int { return dense.count }
+	internal var capacitySparse: Int { return sparse.capacity }
+	internal var capacityDense: Int { return dense.capacity }
 
 	public func contains(_ entityIdx: EntityIndex ) -> Bool {
-		guard let compIdx: ComponentIdx = sparse[entityIdx] else { return false }
-		return compIdx < count && dense[compIdx] != nil
+		return sparse[entityIdx] != nil &&
+			sparse[entityIdx]! < count &&
+			dense[sparse[entityIdx]!] != nil
 	}
 
 	@discardableResult
 	public func add(_ element: Element, with entityIdx: EntityIndex ) -> Bool {
 		if contains(entityIdx) { return false }
-		if needsToGrow(entityIdx) {
-			grow(including: entityIdx)
-		}
 		sparse[entityIdx] = count
 		let entry: Pair = Pair(key: entityIdx, value: element)
 		dense.append(entry)
@@ -52,52 +43,39 @@ public class SparseComponentSet {
 	}
 
 	public func get(at entityIdx: EntityIndex) -> Element? {
-		guard let compIdx: ComponentIdx = sparse[entityIdx] else { return nil }
-		return dense[compIdx]!.value
+		guard contains(entityIdx) else { return nil }
+		return dense[sparse[entityIdx]!]!.value
 	}
 
 	@discardableResult
 	public func remove(_ entityIdx: EntityIndex ) -> Element? {
-		guard let compIdx: ComponentIdx = sparse[entityIdx] else { return nil }
-		let last: Int = count-1
-		dense.swapAt(compIdx, last)
+		guard contains(entityIdx) else { return nil }
+		let compIdx: ComponentIdx = sparse[entityIdx]!
+		let lastIdx: ComponentIdx = count-1
+		dense.swapAt(compIdx, lastIdx)
 		sparse[entityIdx] = nil
 		let swapped: Pair = dense[compIdx]!
 		sparse[swapped.key] = compIdx
 		let removed: Pair = dense.popLast()!!
 		size -= 1
+		if size == 0 {
+			clear(keepingCapacity: false)
+		}
 		return removed.value
 	}
 
 	public func clear(keepingCapacity: Bool = false) {
+		size = 0
 		dense.removeAll(keepingCapacity: keepingCapacity)
+		sparse.removeAll(keepingCapacity: keepingCapacity)
 	}
 
-	fileprivate func needsToGrow(_ index: Int) -> Bool {
-		return index > count - 1
-	}
-
-	fileprivate func grow(including index: Int) {
-		let newCapacity: Int = nearest(to: index)
-		//let newCount: Int = newCapacity-count
-		dense.reserveCapacity(newCapacity)
-		/*for _ in 0..<newCount {
-			dense.append(nil)
-		}*/
-	}
-
-	fileprivate func nearest(to index: Int) -> Int {
-		let delta = Float(index) / Float(chunkSize)
-		let multiplier = Int(delta) + 1
-		return multiplier * chunkSize
-	}
 }
 
 extension SparseComponentSet: Sequence {
 
 	public func makeIterator() -> AnyIterator<Element> {
 		var iterator = dense.makeIterator()
-
 		return AnyIterator<Element> {
 			iterator.next()??.value
 		}