From 6e8c60eabbbf0f21ef8e0b87267952bec2f85159 Mon Sep 17 00:00:00 2001 From: Denton Cockburn Date: Sat, 13 Dec 2014 21:46:25 -0500 Subject: SI-9043 ArrayBuffer.insert and insertAll are very slow insert and insertAll were slower than their java equivalents by factors of 5 and 10 respectively. Benchmark code was provided here: https://gist.github.com/rklaehn/3e9290118fcf63d1feae We are using a toList to the source Traversable Then doing a length and a copy on that collection. By using an array, we can make use of faster methods. Managed to get the ratios down to 1.5 and 1.5 respectively. In addition to this, I think we should consider breaking insert into 2 separate methods, one for a single item and one for a collection. The varags version is very expensive when a single item is being inserted. @phaller @axel22 --- src/library/scala/collection/mutable/ArrayBuffer.scala | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'src') diff --git a/src/library/scala/collection/mutable/ArrayBuffer.scala b/src/library/scala/collection/mutable/ArrayBuffer.scala index 8f77114746..011fd415ee 100644 --- a/src/library/scala/collection/mutable/ArrayBuffer.scala +++ b/src/library/scala/collection/mutable/ArrayBuffer.scala @@ -128,7 +128,7 @@ class ArrayBuffer[A](override protected val initialSize: Int) override def ++=:(xs: TraversableOnce[A]): this.type = { insertAll(0, xs.toTraversable); this } /** Inserts new elements at the index `n`. Opposed to method - * `update`, this method will not replace an element with a + * `update`, this method will not replace an element with a new * one. Instead, it will insert a new element at index `n`. * * @param n the index where a new element will be inserted. @@ -137,12 +137,13 @@ class ArrayBuffer[A](override protected val initialSize: Int) */ def insertAll(n: Int, seq: Traversable[A]) { if (n < 0 || n > size0) throw new IndexOutOfBoundsException(n.toString) - val xs = seq.toList - val len = xs.length - ensureSize(size0 + len) + val len = seq.size + val newSize = size0 + len + ensureSize(newSize) + copy(n, n + len, size0 - n) - xs.copyToArray(array.asInstanceOf[scala.Array[Any]], n) - size0 += len + seq.copyToArray(array.asInstanceOf[Array[Any]], n) + size0 = newSize } /** Removes the element on a given index position. It takes time linear in -- cgit v1.2.3