Optimize finding index of last nonnull trie child in Vector and Builder

Abduqodiri Qurbonzoda · Abduqodiri Qurbonzoda · commit dc5fb3738eb7 · 2019-04-16T02:19:42.000+03:00
diff --git a/kotlinx-collections-immutable/src/main/kotlin/kotlinx/collections/immutable/implementations/immutableList/PersistentVector.kt b/kotlinx-collections-immutable/src/main/kotlin/kotlinx/collections/immutable/implementations/immutableList/PersistentVector.kt
@@ -250,10 +250,9 @@ internal class PersistentVector<E>(private val root: Array<Any?>,
             return newRoot
         }
 
-        // Could be val bufferLastIndex = root.indexOfLast { it != null }, but that isn't optimized enough
         var bufferLastIndex = MAX_BUFFER_SIZE_MINUS_ONE
-        while (root[bufferLastIndex] == null) {
-            bufferLastIndex -= 1
+        if (root[bufferLastIndex] == null) {
+            bufferLastIndex = indexSegment(rootSize() - 1, shift)
         }
 
         val newRoot = root.copyOf(MAX_BUFFER_SIZE)
diff --git a/kotlinx-collections-immutable/src/main/kotlin/kotlinx/collections/immutable/implementations/immutableList/PersistentVectorBuilder.kt b/kotlinx-collections-immutable/src/main/kotlin/kotlinx/collections/immutable/implementations/immutableList/PersistentVectorBuilder.kt
@@ -299,8 +299,8 @@ class PersistentVectorBuilder<E>(private var vector: PersistentList<E>,
         }
 
         var bufferLastIndex = MAX_BUFFER_SIZE_MINUS_ONE
-        while (root[bufferLastIndex] == null) {
-            bufferLastIndex -= 1
+        if (root[bufferLastIndex] == null) {
+            bufferLastIndex = indexSegment(rootSize() - 1, shift)
         }
 
         val mutableRoot = makeMutable(root)

Original file line number	Diff line number	Diff line change
`@@ -250,10 +250,9 @@ internal class PersistentVector<E>(private val root: Array<Any?>,`
`250`	`250`	`return newRoot`
`251`	`251`	`}`
`252`	`252`
`253`		`- // Could be val bufferLastIndex = root.indexOfLast { it != null }, but that isn't optimized enough`
`254`	`253`	`var bufferLastIndex = MAX_BUFFER_SIZE_MINUS_ONE`
`255`		`- while (root[bufferLastIndex] == null) {`
`256`		`- bufferLastIndex -= 1`
	`254`	`+ if (root[bufferLastIndex] == null) {`
	`255`	`+ bufferLastIndex = indexSegment(rootSize() - 1, shift)`
`257`	`256`	`}`
`258`	`257`
`259`	`258`	`val newRoot = root.copyOf(MAX_BUFFER_SIZE)`
Original file line number	Diff line number	Diff line change
`@@ -299,8 +299,8 @@ class PersistentVectorBuilder<E>(private var vector: PersistentList<E>,`
`299`	`299`	`}`
`300`	`300`
`301`	`301`	`var bufferLastIndex = MAX_BUFFER_SIZE_MINUS_ONE`
`302`		`- while (root[bufferLastIndex] == null) {`
`303`		`- bufferLastIndex -= 1`
	`302`	`+ if (root[bufferLastIndex] == null) {`
	`303`	`+ bufferLastIndex = indexSegment(rootSize() - 1, shift)`
`304`	`304`	`}`
`305`	`305`
`306`	`306`	`val mutableRoot = makeMutable(root)`