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Added parFlatMapN #4243

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merged 9 commits into from
Oct 7, 2022
Merged

Added parFlatMapN #4243

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a0e0efb
Added flatParMapN
TonioGela Jun 17, 2022
fe96ffa
Added flatParMapN tests for 1-arity
TonioGela Jun 18, 2022
f62d98b
Refactored .map.flatten in to .flatmap
TonioGela Jun 21, 2022
997e803
Modified function name as per discussion
TonioGela Sep 17, 2022
06ac73b
Added ParallelSuite tests for parFlatMapN
TonioGela Sep 20, 2022
5e41658
Changed implementation using arity functions
TonioGela Sep 27, 2022
adbb470
Rewrote test for clarity
TonioGela Sep 28, 2022
c8b6cd0
Autogenerating the test function itself
TonioGela Sep 28, 2022
325b4b4
Generalizing all the parFlatMap tests
TonioGela Oct 6, 2022
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10 changes: 10 additions & 0 deletions project/Boilerplate.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -349,6 +349,9 @@ object Boilerplate {
- /** @group ParMapArity */
- def parMap$arity[M[_], ${`A..N`}, Z]($fparams)(f: (${`A..N`}) => Z)(implicit p: NonEmptyParallel[M]): M[Z] =
- p.flatMap.map(${nestedExpansion.products}) { case ${nestedExpansion.`(a..n)`} => f(${`a..n`}) }
-
- def flatParMap$arity[M[_], ${`A..N`}, Z]($fparams)(f: (${`A..N`}) => M[Z])(implicit p: NonEmptyParallel[M]): M[Z] =
- p.flatMap.flatten(p.flatMap.map(${nestedExpansion.products}) { case ${nestedExpansion.`(a..n)`} => f(${`a..n`}) })
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@armanbilge armanbilge Jun 17, 2022 •
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Not directly about this PR, but I'm confused by the code here (also for the existing method above it). Why is it calling p.flatMap.map instead of p.apply.map? Since the Apply is the parallel instance.

Am I confused or is this a bug? Maybe we need some tests using e.g. EitherNec[String, A]?

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Yes agree, good catch... So now I wonder too.

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@armanbilge armanbilge Jun 18, 2022 •
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Ahh, no this is completely fine. It's because it's calling vanilla map on a single argument (a tuple), which is then unpacked by the case in the lambda. I was mistakenly reading it as calling a mapN-like method, in which case this would be wrong.

The map must be consistent between the flatMap and the apply by law, and using the apply instance would require a conversion to the parallel datatype and back. So it's an optimization to use the one from the flatMap instead.

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Actually ... this is just flatMap ... right? 😂

Suggested change
- p.flatMap.map(${nestedExpansion.products}) { case ${nestedExpansion.`(a..n)`} => f(${`a..n`}) }
-
- def flatParMap$arity[M[_], ${`A..N`}, Z]($fparams)(f: (${`A..N`}) => M[Z])(implicit p: NonEmptyParallel[M]): M[Z] =
- p.flatMap.flatten(p.flatMap.map(${nestedExpansion.products}) { case ${nestedExpansion.`(a..n)`} => f(${`a..n`}) })
- p.flatMap.map(${nestedExpansion.products}) { case ${nestedExpansion.`(a..n)`} => f(${`a..n`}) }
-
- def flatParMap$arity[M[_], ${`A..N`}, Z]($fparams)(f: (${`A..N`}) => M[Z])(implicit p: NonEmptyParallel[M]): M[Z] =
- p.flatMap.flatMap(${nestedExpansion.products}) { case ${nestedExpansion.`(a..n)`} => f(${`a..n`}) }

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It is! I run the tests locally just to be sure that I was not missing something syntax related :)

|}
"""
}
Expand Down Expand Up @@ -472,6 +475,12 @@ object Boilerplate {
else
s"def parMapN[Z](f: (${`A..N`}) => Z)(implicit p: NonEmptyParallel[M]): M[Z] = Parallel.parMap$arity($tupleArgs)(f)"

val flatParMap =
if (arity == 1)
s"def flatParMap[Z](f: (${`A..N`}) => M[Z])(implicit p: NonEmptyParallel[M]): M[Z] = p.flatMap.flatMap($tupleArgs)(f)"
else
s"def flatParMapN[Z](f: (${`A..N`}) => M[Z])(implicit p: NonEmptyParallel[M]): M[Z] = p.flatMap.flatten(Parallel.parMap$arity($tupleArgs)(f))"

val parTupled =
if (arity == 1) ""
else
Expand All @@ -490,6 +499,7 @@ object Boilerplate {
-private[syntax] final class Tuple${arity}ParallelOps[M[_], ${`A..N`}](private val $tupleTpe) extends Serializable {
- $parMap
- $parTupled
- $flatParMap
-}
|
"""
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4 changes: 4 additions & 0 deletions tests/shared/src/test/scala/cats/tests/SyntaxSuite.scala
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Expand Up @@ -246,9 +246,13 @@ object SyntaxSuite {
val fb = mock[M[B]]
val fc = mock[M[C]]
val f = mock[(A, B, C) => Z]
val mf = mock[(A, B, C) => M[Z]]

tfabc.parMapN(f)
(fa, fb, fc).parMapN(f)

tfabc.flatParMapN(mf)
(fa, fb, fc).flatParMapN(mf)
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}

def testParallelBi[M[_], F[_], T[_, _]: Bitraverse, A, B, C, D](implicit P: Parallel.Aux[M, F]): Unit = {
Expand Down