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Parallel map2 optimization #3428

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merged 12 commits into from
Apr 20, 2023
Merged

Parallel map2 optimization #3428

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f3881a9
Add parallel map2 test
durban Feb 17, 2023
d7ee73f
The same test for PureConc
durban Feb 17, 2023
e86aef7
Kick CI
durban Feb 17, 2023
4393611
More test
durban Feb 17, 2023
5b2a804
More tests
durban Feb 17, 2023
4995c29
Kick CI
durban Feb 17, 2023
9e9d015
Go back to the old map2 implementation
durban Feb 17, 2023
cb80099
scalafmt
durban Feb 20, 2023
2c4bc68
New map2 implementation
durban Feb 17, 2023
5ffdb35
Temporarily disable 2 PureConc tests (probably issue #3430)
durban Feb 20, 2023
35c8c43
Go back to the old map2 implementation again
durban Apr 19, 2023
43b8459
Merge from series/3.4.x
durban Apr 19, 2023
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139 changes: 5 additions & 134 deletions kernel/shared/src/main/scala/cats/effect/kernel/instances/GenSpawnInstances.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -16,9 +16,9 @@

package cats.effect.kernel.instances

import cats.{~>, Align, Applicative, CommutativeApplicative, Eval, Functor, Monad, Parallel}
import cats.{~>, Align, Applicative, CommutativeApplicative, Functor, Monad, Parallel}
import cats.data.Ior
import cats.effect.kernel.{GenSpawn, Outcome, ParallelF}
import cats.effect.kernel.{GenSpawn, ParallelF}
import cats.implicits._

trait GenSpawnInstances {
Expand All @@ -41,7 +41,6 @@ trait GenSpawnInstances {
new (M ~> F) {
def apply[A](ma: M[A]): F[A] = ParallelF[M, A](ma)
}

}

implicit def commutativeApplicativeForParallelF[F[_], E](
Expand All @@ -51,134 +50,10 @@ trait GenSpawnInstances {
final override def pure[A](a: A): ParallelF[F, A] = ParallelF(F.pure(a))

final override def map2[A, B, Z](fa: ParallelF[F, A], fb: ParallelF[F, B])(
f: (A, B) => Z): ParallelF[F, Z] =
f: (A, B) => Z): ParallelF[F, Z] = {
ParallelF(
F.uncancelable { poll =>
for {
fiberA <- F.start(ParallelF.value(fa))
fiberB <- F.start(ParallelF.value(fb))

// start a pair of supervisors to ensure that the opposite is canceled on error
_ <- F start {
fiberB.join flatMap {
case Outcome.Succeeded(_) => F.unit
case _ => fiberA.cancel
}
}

_ <- F start {
fiberA.join flatMap {
case Outcome.Succeeded(_) => F.unit
case _ => fiberB.cancel
}
}

a <- F
.onCancel(poll(fiberA.join), bothUnit(fiberA.cancel, fiberB.cancel))
.flatMap[A] {
case Outcome.Succeeded(fa) =>
fa

case Outcome.Errored(e) =>
fiberB.cancel *> F.raiseError(e)

case Outcome.Canceled() =>
fiberB.cancel *> poll {
fiberB.join flatMap {
case Outcome.Succeeded(_) | Outcome.Canceled() =>
F.canceled *> F.never
case Outcome.Errored(e) =>
F.raiseError(e)
}
}
}

z <- F.onCancel(poll(fiberB.join), fiberB.cancel).flatMap[Z] {
case Outcome.Succeeded(fb) =>
fb.map(b => f(a, b))

case Outcome.Errored(e) =>
F.raiseError(e)

case Outcome.Canceled() =>
poll {
fiberA.join flatMap {
case Outcome.Succeeded(_) | Outcome.Canceled() =>
F.canceled *> F.never
case Outcome.Errored(e) =>
F.raiseError(e)
}
}
}
} yield z
}
)

final override def map2Eval[A, B, Z](fa: ParallelF[F, A], fb: Eval[ParallelF[F, B]])(
f: (A, B) => Z): Eval[ParallelF[F, Z]] =
Eval.now(
ParallelF(
F.uncancelable { poll =>
for {
fiberA <- F.start(ParallelF.value(fa))
fiberB <- F.start(ParallelF.value(fb.value))

// start a pair of supervisors to ensure that the opposite is canceled on error
_ <- F start {
fiberB.join flatMap {
case Outcome.Succeeded(_) => F.unit
case _ => fiberA.cancel
}
}

_ <- F start {
fiberA.join flatMap {
case Outcome.Succeeded(_) => F.unit
case _ => fiberB.cancel
}
}

a <- F
.onCancel(poll(fiberA.join), bothUnit(fiberA.cancel, fiberB.cancel))
.flatMap[A] {
case Outcome.Succeeded(fa) =>
fa

case Outcome.Errored(e) =>
fiberB.cancel *> F.raiseError(e)

case Outcome.Canceled() =>
fiberB.cancel *> poll {
fiberB.join flatMap {
case Outcome.Succeeded(_) | Outcome.Canceled() =>
F.canceled *> F.never
case Outcome.Errored(e) =>
F.raiseError(e)
}
}
}

z <- F.onCancel(poll(fiberB.join), fiberB.cancel).flatMap[Z] {
case Outcome.Succeeded(fb) =>
fb.map(b => f(a, b))

case Outcome.Errored(e) =>
F.raiseError(e)

case Outcome.Canceled() =>
poll {
fiberA.join flatMap {
case Outcome.Succeeded(_) | Outcome.Canceled() =>
F.canceled *> F.never
case Outcome.Errored(e) =>
F.raiseError(e)
}
}
}
} yield z
}
)
)
F.both(ParallelF.value(fa), ParallelF.value(fb)).map { case (a, b) => f(a, b) })
}

final override def ap[A, B](ff: ParallelF[F, A => B])(
fa: ParallelF[F, A]): ParallelF[F, B] =
Expand All @@ -194,10 +69,6 @@ trait GenSpawnInstances {

final override def unit: ParallelF[F, Unit] =
ParallelF(F.unit)

// assumed to be uncancelable
private[this] def bothUnit(a: F[Unit], b: F[Unit]): F[Unit] =
F.start(a).flatMap(f => b *> f.join.void)
}

implicit def alignForParallelF[F[_], E](implicit F: GenSpawn[F, E]): Align[ParallelF[F, *]] =
Expand Down
7 changes: 7 additions & 0 deletions laws/shared/src/test/scala/cats/effect/laws/PureConcSpec.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,13 @@ class PureConcSpec extends Specification with Discipline with BaseSpec {
pure.run((F.raiseError[Unit](42), F.never[Unit]).parTupled) mustEqual Outcome.Errored(42)
}

"short-circuit on canceled" in {
pure.run((F.never[Unit], F.canceled).parTupled.start.flatMap(_.join)) mustEqual Outcome
.Succeeded(Some(Outcome.canceled[F, Nothing, Unit]))
pure.run((F.canceled, F.never[Unit]).parTupled.start.flatMap(_.join)) mustEqual Outcome
.Succeeded(Some(Outcome.canceled[F, Nothing, Unit]))
}

"not run forever on chained product" in {
import cats.effect.kernel.Par.ParallelF

Expand Down
75 changes: 75 additions & 0 deletions tests/shared/src/test/scala/cats/effect/IOSpec.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1314,6 +1314,81 @@ class IOSpec extends BaseSpec with Discipline with IOPlatformSpecification {
(IO.raiseError[Unit](TestException), IO.never[Unit]).parTupled.void must failAs(
TestException)
}

"short-circuit on canceled" in ticked { implicit ticker =>
(IO.never[Unit], IO.canceled)
.parTupled
.start
.flatMap(_.join.map(_.isCanceled)) must completeAs(true)
(IO.canceled, IO.never[Unit])
.parTupled
.start
.flatMap(_.join.map(_.isCanceled)) must completeAs(true)
}

"run finalizers when canceled" in ticked { implicit ticker =>
val tsk = IO.ref(0).flatMap { ref =>
val t = IO.never[Unit].onCancel(ref.update(_ + 1))
for {
fib <- (t, t).parTupled.start
_ <- IO { ticker.ctx.tickAll() }
_ <- fib.cancel
c <- ref.get
} yield c
}

tsk must completeAs(2)
}

"run right side finalizer when canceled (and left side already completed)" in ticked {
implicit ticker =>
val tsk = IO.ref(0).flatMap { ref =>
for {
fib <- (IO.unit, IO.never[Unit].onCancel(ref.update(_ + 1))).parTupled.start
_ <- IO { ticker.ctx.tickAll() }
_ <- fib.cancel
c <- ref.get
} yield c
}

tsk must completeAs(1)
}

"run left side finalizer when canceled (and right side already completed)" in ticked {
implicit ticker =>
val tsk = IO.ref(0).flatMap { ref =>
for {
fib <- (IO.never[Unit].onCancel(ref.update(_ + 1)), IO.unit).parTupled.start
_ <- IO { ticker.ctx.tickAll() }
_ <- fib.cancel
c <- ref.get
} yield c
}

tsk must completeAs(1)
}

"complete if both sides complete" in ticked { implicit ticker =>
val tsk = (
IO.sleep(2.seconds).as(20),
IO.sleep(3.seconds).as(22)
).parTupled.map { case (l, r) => l + r }

tsk must completeAs(42)
}

"not run forever on chained product" in ticked { implicit ticker =>
import cats.effect.kernel.Par.ParallelF

case object TestException extends RuntimeException

val fa: IO[String] = IO.pure("a")
val fb: IO[String] = IO.pure("b")
val fc: IO[Unit] = IO.raiseError[Unit](TestException)
val tsk =
ParallelF.value(ParallelF(fa).product(ParallelF(fb)).product(ParallelF(fc))).void
tsk must failAs(TestException)
}
}

"miscellaneous" should {
Expand Down