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Experiment: use immutable data structures in optimized traverse
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Is this necessary? The monad laws should ensure that it's safe to use
mutable builders. Nonetheless it will be good to confirm the performance
delta for using immutable data structures
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@TimWSpence
TimWSpence committed Nov 8, 2023
1 parent a1c9ff5 commit b92a558
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Showing 8 changed files with 27 additions and 38 deletions.
4 changes: 2 additions & 2 deletions core/src/main/scala-2.13+/cats/instances/arraySeq.scala
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Expand Up @@ -104,7 +104,7 @@ private[cats] object ArraySeqInstances {
def traverse[G[_], A, B](fa: ArraySeq[A])(f: A => G[B])(implicit G: Applicative[G]): G[ArraySeq[B]] =
G match {
case x: StackSafeMonad[G] =>
x.map(Traverse.traverseDirectly(Vector.newBuilder[B])(fa.iterator)(f)(x))(_.to(ArraySeq.untagged))
x.map(Traverse.traverseDirectly(fa.iterator)(f)(x))(_.to(ArraySeq.untagged))
case _ =>
G.map(Chain.traverseViaChain(fa)(f))(_.iterator.to(ArraySeq.untagged))

Expand Down Expand Up @@ -233,7 +233,7 @@ private[cats] object ArraySeqInstances {
)(f: (A) => G[Option[B]])(implicit G: Applicative[G]): G[ArraySeq[B]] =
G match {
case x: StackSafeMonad[G] =>
x.map(TraverseFilter.traverseFilterDirectly(Vector.newBuilder[B])(fa.iterator)(f)(x))(
x.map(TraverseFilter.traverseFilterDirectly(fa.iterator)(f)(x))(
_.to(ArraySeq.untagged)
)
case _ =>
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20 changes: 7 additions & 13 deletions core/src/main/scala/cats/Traverse.scala
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Expand Up @@ -25,7 +25,6 @@ import cats.data.State
import cats.data.StateT
import cats.kernel.compat.scalaVersionSpecific._
import cats.StackSafeMonad
import scala.collection.mutable

/**
* Traverse, also known as Traversable.
Expand Down Expand Up @@ -287,21 +286,16 @@ object Traverse {
@deprecated("Use cats.syntax object imports", "2.2.0")
object nonInheritedOps extends ToTraverseOps

private[cats] def traverseDirectly[Coll[x] <: IterableOnce[x], G[_], A, B](
builder: mutable.Builder[B, Coll[B]]
)(fa: IterableOnce[A])(f: A => G[B])(implicit G: StackSafeMonad[G]): G[Coll[B]] = {
val size = fa.knownSize
if (size >= 0) {
builder.sizeHint(size)
}
G.map(fa.iterator.foldLeft(G.pure(builder)) { case (accG, a) =>
private[cats] def traverseDirectly[G[_], A, B](
fa: IterableOnce[A]
)(f: A => G[B])(implicit G: StackSafeMonad[G]): G[Vector[B]] = {
fa.iterator.foldLeft(G.pure(Vector.empty[B])) { case (accG, a) =>
G.flatMap(accG) { acc =>
G.map(f(a)) { a =>
acc += a
acc
G.map(f(a)) { b =>
acc.appended(b)
}
}
})(_.result())
}
}

private[cats] def traverse_Directly[G[_], A, B](
Expand Down
21 changes: 8 additions & 13 deletions core/src/main/scala/cats/TraverseFilter.scala
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Expand Up @@ -25,7 +25,6 @@ import cats.data.State
import cats.kernel.compat.scalaVersionSpecific._

import scala.collection.immutable.{IntMap, TreeSet}
import scala.collection.mutable

/**
* `TraverseFilter`, also known as `Witherable`, represents list-like structures
Expand Down Expand Up @@ -205,21 +204,17 @@ object TraverseFilter {
@deprecated("Use cats.syntax object imports", "2.2.0")
object nonInheritedOps extends ToTraverseFilterOps

private[cats] def traverseFilterDirectly[Coll[x] <: IterableOnce[x], G[_], A, B](
builder: mutable.Builder[B, Coll[B]]
)(fa: IterableOnce[A])(f: A => G[Option[B]])(implicit G: StackSafeMonad[G]): G[Coll[B]] = {
val size = fa.knownSize
if (size >= 0) {
builder.sizeHint(size)
}
G.map(fa.iterator.foldLeft(G.pure(builder)) { case (bldrG, a) =>
G.flatMap(bldrG) { bldr =>
private[cats] def traverseFilterDirectly[G[_], A, B](
fa: IterableOnce[A]
)(f: A => G[Option[B]])(implicit G: StackSafeMonad[G]): G[Vector[B]] = {
fa.iterator.foldLeft(G.pure(Vector.empty[B])) { case (bldrG, a) =>
G.flatMap(bldrG) { acc =>
G.map(f(a)) {
case Some(b) => bldr += b
case None => bldr
case Some(b) => acc.appended(b)
case None => acc
}
}
})(_.result())
}
}

}
4 changes: 2 additions & 2 deletions core/src/main/scala/cats/data/Chain.scala
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Expand Up @@ -1243,7 +1243,7 @@ sealed abstract private[data] class ChainInstances extends ChainInstances1 {
else
G match {
case x: StackSafeMonad[G] =>
x.map(Traverse.traverseDirectly(List.newBuilder[B])(fa.iterator)(f)(x))(Chain.fromSeq(_))
x.map(Traverse.traverseDirectly(fa.iterator)(f)(x))(Chain.fromSeq(_))
case _ =>
traverseViaChain {
val as = collection.mutable.ArrayBuffer[A]()
Expand Down Expand Up @@ -1372,7 +1372,7 @@ sealed abstract private[data] class ChainInstances extends ChainInstances1 {
else
G match {
case x: StackSafeMonad[G] =>
G.map(TraverseFilter.traverseFilterDirectly(List.newBuilder[B])(fa.iterator)(f)(x))(Chain.fromSeq(_))
G.map(TraverseFilter.traverseFilterDirectly(fa.iterator)(f)(x))(Chain.fromSeq(_))
case _ =>
traverseFilterViaChain {
val as = collection.mutable.ArrayBuffer[A]()
Expand Down
4 changes: 2 additions & 2 deletions core/src/main/scala/cats/instances/list.scala
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Expand Up @@ -122,7 +122,7 @@ trait ListInstances extends cats.kernel.instances.ListInstances {
if (fa.isEmpty) G.pure(Nil)
else
G match {
case x: StackSafeMonad[G] => Traverse.traverseDirectly[List, G, A, B](ListBuffer.empty[B])(fa)(f)(x)
case x: StackSafeMonad[G] => G.map(Traverse.traverseDirectly[G, A, B](fa)(f)(x))(_.toList)
case _ =>
G.map(Chain.traverseViaChain {
val as = collection.mutable.ArrayBuffer[A]()
Expand Down Expand Up @@ -320,7 +320,7 @@ private[instances] trait ListInstancesBinCompat0 {
if (fa.isEmpty) G.pure(Nil)
else
G match {
case x: StackSafeMonad[G] => TraverseFilter.traverseFilterDirectly(List.newBuilder[B])(fa)(f)(x)
case x: StackSafeMonad[G] => x.map(TraverseFilter.traverseFilterDirectly(fa)(f)(x))(_.toList)
case _ =>
G.map(Chain.traverseFilterViaChain {
val as = collection.mutable.ArrayBuffer[A]()
Expand Down
4 changes: 2 additions & 2 deletions core/src/main/scala/cats/instances/queue.scala
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Expand Up @@ -122,7 +122,7 @@ trait QueueInstances extends cats.kernel.instances.QueueInstances {
if (fa.isEmpty) G.pure(Queue.empty[B])
else
G match {
case x: StackSafeMonad[G] => Traverse.traverseDirectly(Queue.newBuilder[B])(fa)(f)(x)
case x: StackSafeMonad[G] => G.map(Traverse.traverseDirectly(fa)(f)(x))(Queue.from(_))
case _ =>
G.map(Chain.traverseViaChain {
val as = collection.mutable.ArrayBuffer[A]()
Expand Down Expand Up @@ -239,7 +239,7 @@ private object QueueInstances {
if (fa.isEmpty) G.pure(Queue.empty[B])
else
G match {
case x: StackSafeMonad[G] => TraverseFilter.traverseFilterDirectly(Queue.newBuilder[B])(fa)(f)(x)
case x: StackSafeMonad[G] => x.map(TraverseFilter.traverseFilterDirectly(fa)(f)(x))(Queue.from(_))
case _ =>
G.map(Chain.traverseFilterViaChain {
val as = collection.mutable.ArrayBuffer[A]()
Expand Down
4 changes: 2 additions & 2 deletions core/src/main/scala/cats/instances/seq.scala
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Expand Up @@ -129,7 +129,7 @@ trait SeqInstances extends cats.kernel.instances.SeqInstances {
final override def traverse[G[_], A, B](fa: Seq[A])(f: A => G[B])(implicit G: Applicative[G]): G[Seq[B]] =
G match {
case x: StackSafeMonad[G] =>
Traverse.traverseDirectly(Seq.newBuilder[B])(fa)(f)(x)
x.map(Traverse.traverseDirectly(fa)(f)(x))(_.toSeq)
case _ =>
G.map(Chain.traverseViaChain(fa.toIndexedSeq)(f))(_.toVector)
}
Expand Down Expand Up @@ -210,7 +210,7 @@ trait SeqInstances extends cats.kernel.instances.SeqInstances {

def traverseFilter[G[_], A, B](fa: Seq[A])(f: (A) => G[Option[B]])(implicit G: Applicative[G]): G[Seq[B]] =
G match {
case x: StackSafeMonad[G] => TraverseFilter.traverseFilterDirectly(Seq.newBuilder[B])(fa)(f)(x)
case x: StackSafeMonad[G] => x.map(TraverseFilter.traverseFilterDirectly(fa)(f)(x))(_.toSeq)
case _ =>
G.map(Chain.traverseFilterViaChain(fa.toIndexedSeq)(f))(_.toVector)
}
Expand Down
4 changes: 2 additions & 2 deletions core/src/main/scala/cats/instances/vector.scala
View file
Expand Up @@ -126,7 +126,7 @@ trait VectorInstances extends cats.kernel.instances.VectorInstances {

final override def traverse[G[_], A, B](fa: Vector[A])(f: A => G[B])(implicit G: Applicative[G]): G[Vector[B]] =
G match {
case x: StackSafeMonad[G] => Traverse.traverseDirectly(Vector.newBuilder[B])(fa)(f)(x)
case x: StackSafeMonad[G] => Traverse.traverseDirectly(fa)(f)(x)
case _ => G.map(Chain.traverseViaChain(fa)(f))(_.toVector)
}

Expand Down Expand Up @@ -271,7 +271,7 @@ private[instances] trait VectorInstancesBinCompat0 {

def traverseFilter[G[_], A, B](fa: Vector[A])(f: (A) => G[Option[B]])(implicit G: Applicative[G]): G[Vector[B]] =
G match {
case x: StackSafeMonad[G] => TraverseFilter.traverseFilterDirectly(Vector.newBuilder[B])(fa)(f)(x)
case x: StackSafeMonad[G] => TraverseFilter.traverseFilterDirectly(fa)(f)(x)
case _ =>
G.map(Chain.traverseFilterViaChain(fa)(f))(_.toVector)
}
Expand Down

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