many ref updates

LotORef.scala

//> using lib "org.typelevel::cats-effect:3.4.5"

import cats.effect.{IO, IOApp, Sync}
import cats.effect.kernel.Ref
import cats.syntax.all._

class Worker[F[_]](id: Int, ref: Ref[F, Int])(implicit F: Sync[F]) {

  private def putStrLn(value: String): F[Unit] =
    F.blocking(println(value))

  def start: F[Unit] =
    for {
      c1 <- ref.get
      _  <- putStrLn(show"Worker #$id >> $c1")
      c2 <- ref.updateAndGet(x => x + 1)
      _  <- putStrLn(show"Worker #$id >> $c2")
    } yield ()
}

object RefExample extends IOApp.Simple {

  val run: IO[Unit] =
    for {
      ref <- Ref[IO].of(0)
      w1 = new Worker[IO](1, ref)
      w2 = new Worker[IO](2, ref)
      w3 = new Worker[IO](3, ref)
      _ <- List(
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
        w1.start,
        w2.start,
        w3.start,
      ).parSequence.void
    } yield ()
}