require "concurrent/enumerable"

(1..50).parallel.select(&.even?).map { |n| n + 1 }.serial.sum
                 ^               ^                 ^ Results joined.
                 |               | Spawns separate fiber pool
                 | Spawns fiber pool

(1..50).parallel.map { |n|
  # Parallel processing in a fiber pool
  Choose::A::ORM.new(id: n)
}.batch(10).run { |array_of_records|
  # Run 10 Inserts inside a transaction for faster db writes
  # Real applications should choose ~~~100-100000 depending on the database, schema, data & hardware
  ORM.transaction { array_of_records.each &.save! }
}.wait

require "concurrent/channel"

# Same interface and restrictions as concurrent/enumerable.

ch = Channel(Int32).new

spawn do
  10.times { |i| ch.send 1 }
  ch.close
end

# map is processed in a Fiber pool.
# All other fibers will shut down after all messages are processed.
# Any errors in processing are raised here.
ch.parallel.map { |n| n + 1 }.serial.sum

require "concurrent/channel"

# Same interface and restrictions as concurrent/enumerable.

ch = Channel(Int32).new
# Messages may be processed in parallel within each `tee` and `run`.
# Make sure to use immutable objects or concurrency safe data structures.
run = ch.parallel.tee { |n| Log.info { "n=#{n}" } }.batch(2).run { |n| p n }

10.times { |i| ch.send 1 }
ch.close

# Wait until all messages/errors are processed.
run.wait

ary = (1..10).to_a.parallel.select { |i|
  raise "select error" if i == 2
  true
}.parallel.map { |i|
  raise "map error" if i.even?
  i.to_s
# All errors in prior blocks handled here
}.errors { |ex, obj|
  puts "#{obj} #{ex}"
}.map { |s|
  s.to_i
}.to_a

p ary => [1, 3, 5, 7]

require "concurrent/count_down_latch"

fiber_count = 10
latch = Concurrent::CountDownLatch.new
10.times do
  spawn do
    # Do work
    latch.count_down
  end
end

latch.wait_count = fiber_count
latch.wait

require "concurrent/semaphore"

sem = Concurrent::Semaphore.new n

# spawn a lot of fibers
2000.times do
  spawn do
    sem.acquire do
      ...
    end
  end
end