by multiple process and the resources that are used by them - Needs to jump out of the isolated memory space - Isolating processes is one thing, but for the others...
write Threads Try best to be very careful not to change memories of other threads - Tend to change it whenever you lose focus - Only change the places that are okay to change
[4, 5] [5, 8] [6, 13] [7, 21] [8, 34] [9, 55] Plain Fibonacci - Easy to write with Loop def fibonacci(n) a, b = 1, 1 n.times do |i| p [i, a] a, b = b, a + b end end fibonacci(10)
1 while true Fiber.yield(a) a, b = b, a + b end end 10.times do |n| p [n, fib.resume] end def fibonacci(n) a, b = 1, 1 n.times do |i| p [i, a] a, b = b, a + b end end fibonacci(10) Rewrite with Fiber - Explain API using this
1, 1 while true Fiber.yield(a) a, b = b, a + b end end 10.times do |n| p [n, fib.resume] end Fiber.new - Pass value with another Fiber to do a different job - The block code will not run yet.
1, 1 while true Fiber.yield(a) a, b = b, a + b end end 10.times do |n| p [n, fib.resume] end Switch to fiber.resume The argument becomes the value of the fiber
1, 1 while true Fiber.yield(a) a, b = b, a + b end end 10.times do |n| p [n, fib.resume] end resume, again From the second time on, resume restarts from yield
Would not execute just by Fiber new Pass the value to Fiber by resume -- Back to the top on the first round -- Back to Fiber.yield from the second round on --- Which round am I on...?
1 while true Fiber.yield(a) a, b = b, a + b end end 10.times do |n| p [n, fib.resume] end def fibonacci a, b = 1, 1 while true yield(a) a, b = b, a + b end end fib = to_enum(:fibonacci) 10.times do |n| p [n, fib.next] end Rewrite with Enumerator - Nearly identical
do |n| sleep(rand) q.push(n) p [:push, n] end end Thread.new do 10.times do |n| sleep(rand) p [:pop, q.pop] end end.join Sync with Queue - Multiple Threads synchronize through Queue - Each Thread does not know anything about other Threads - Works with multiple producers and consumers
do |n| rdv.push(n) p [:push, n] end end.resume Fiber.new do 10.times do |n| p [:pop, rdv.pop] end end.resume Fiber version - Multiple Fibers work together through Rdv - rendez-vous
= [] end def push(it) if @reader.empty? @writer << [it, Fiber.current] return Fiber.yield end @reader.shift.resume(it) end def pop if @writer.empty? @reader << Fiber.current return Fiber.yield end value, fiber = @writer.shift fiber.resume return value end Implementation of Rdv
[] end def push(it) if @reader.empty? @writer << [it, Fiber.current] return Fiber.yield end @reader.shift.resume(it) end def pop if @writer.empty? @reader << Fiber.current return Fiber.yield end value, fiber = @writer.shift fiber.resume return value end @reader holds fibers waiting for pop @writer holds fibers waiting for push
= [] @writer = [] end def push(it) if @reader.empty? @writer << [it, Fiber.current] return Fiber.yield end @reader.shift.resume(it) end def pop if @writer.empty? @reader << Fiber.current return Fiber.yield end value, fiber = @writer.shift fiber.resume return value end - When there is no @reader, it records itself and wait (yield) - Resume when @reader is present (resume)
end def push(it) if @reader.empty? @writer << [it, Fiber.current] return Fiber.yield end @reader.shift.resume(it) end def pop if @writer.empty? @reader << Fiber.current return Fiber.yield end value, fiber = @writer.shift fiber.resume return value end When @reader is not there - Records the data and Fiber.current, then yield
[] end def push(it) if @reader.empty? @writer << [it, Fiber.current] return Fiber.yield end @reader.shift.resume(it) end def pop if @writer.empty? @reader << Fiber.current return Fiber.yield end value, fiber = @writer.shift fiber.resume return value end @reader is present - Resume one @reader -- Fiber that was waiting for the pop resumes
initialize @reader = [] @writer = [] end def push(it) if @reader.empty? @writer << [it, Fiber.current] return Fiber.yield end @reader.shift.resume(it) end def pop if @writer.empty? @reader << Fiber.current return Fiber.yield end value, fiber = @writer.shift fiber.resume return value end When there is no @writer, it records itself and waits (yield) - When @writer is present, it resumes (resume) -- and returns data Skip!
end def push(it) if @reader.empty? @writer << [it, Fiber.current] return Fiber.yield end @reader.shift.resume(it) end def pop if @writer.empty? @reader << Fiber.current return Fiber.yield end value, fiber = @writer.shift fiber.resume return value end @writer is gone Record Fiber.current and yield Skip!
= [] end def push(it) if @reader.empty? @writer << [it, Fiber.current] return Fiber.yield end @reader.shift.resume(it) end def pop if @writer.empty? @reader << Fiber.current return Fiber.yield end value, fiber = @writer.shift fiber.resume return value end @writer is present - Resume one @writer -- a Fiber that was waiting for push resumes - Returns data value from the note Skip!
[] end def push(it) if @reader.empty? @writer << [it, Fiber.current] return Fiber.yield end @reader.shift.resume(it) end def pop if @writer.empty? @reader << Fiber.current return Fiber.yield end value, fiber = @writer.shift fiber.resume return value end Exclusive control while inspecting - With Fiber, there is no need for exclusive control - Very risky on Threads!!
p [:push, n] end end.resume Fiber.new do 10.times do |n| p [:pop, rdv.pop] end end.resume How it works. Fiber.new kara-matz is summoned! Fiber.newした kara-matzを召喚
p [:push, n] end end.resume Fiber.new do 10.times do |n| p [:pop, rdv.pop] end end.resume kara-matz is resumed It's kara-matz's turn! kara-matzをresume kara-matzのターン
p [:push, n] end end.resume Fiber.new do 10.times do |n| p [:pop, rdv.pop] end end.resume kara-matz does push() There are no opponents.. Record data and himself, then yield. kara-matzのpush！ 相手がいない。 自分とデータをメモしyield。ターン終了
p [:push, n] end end.resume Fiber.new do 10.times do |n| p [:pop, rdv.pop] end end.resume Main's turn! Fiber.new ichi-matz is summoned! メインのターン Fiber.new ichi-matzを召喚
p [:push, n] end end.resume Fiber.new do 10.times do |n| p [:pop, rdv.pop] end end.resume ichi-matz resumed It's ichi-matz's turn! ichi-matzをresume ichi-matzのターン
p [:push, n] end end.resume Fiber.new do 10.times do |n| p [:pop, rdv.pop] end end.resume ichi-matz does pop! ichi-matz reads the memo takes data. kara-matz resumes the finished. ichi-matzのpop！ ichi-matzはメモを読んだ データを手にいれた。kara-matzをresumeしターン終了
p [:push, n] end end.resume Fiber.new do 10.times do |n| p [:pop, rdv.pop] end end.resume kara-matz does push() There are no opponents. Record data and himself, then yield. kara-matzのpush！ 相手がいない。 自分とデータをメモしyield。ターン終了
p [:push, n] end end.resume Fiber.new do 10.times do |n| p [:pop, rdv.pop] end end.resume ichi-matzのpop！ ichi-matzはメモを読んだ データを手にいれた。kara-matzをresumeしターン終了 ichi-matz does pop! ichi-matz reads the memo takes data. kara-matz resumes the finished. Skip!
p [:push, n] end end.resume Fiber.new do 10.times do |n| p [:pop, rdv.pop] end end.resume ichi-matz dies. It's main's turn Main dies. ichi-matzはしんでしまった メインのターン メインはしんでしまった Skip!
exclusive control when sync-ing - Don't want it to be implicitly converted into Threads -- It's better off that it was actually Fiber when you thought you were using Threads
explain with dRuby server pseudo code - Coding is simple, but doesn't move in parallel - Works in parallel with Threads - Code above rewritten to use Fiber (bit awkward) -- Better version using Fiber
do |fd| call_callback end end end def on_accept c = accept loop do read_request(c) do_it write_response(c) end end Simple but not parallel - Written straight forward - Ignore I/O blocks - Only works with one client def read_n(fd, sz) ... ... end
|fd| call_callback end end end def on_accept c = accept Thread.new(c) do |fd| loop do read_request(fd) do_it write_response(fd) end end end Thread ver - Start a new thread on every fd - Add 2 columns and it works in parallel def read_n(fd, sz) ... ... end Ճ͚ͩ͜͜ Ճ͚ͩ͜͜
|fd| call_callback end end end def on_accept c = accept Fiber.new do loop do read_request(c) do_it write_response(c) end end.resume end Fiber ver - non-preemptive - Not quite parallel, yet def read_n(fd, sz) ... ... end Swapped with Fiber
do |fd| call_callback end end end def on_accept c = accept Fiber.new do loop do read_request(c) do_it write_response(c) end end.resume end Fiber ver Revisioned - Switch context before it I/O blocks -- Blocking-style non-blocking I/O def read_n(fd, sz) ... fd.read_nonblock(sz) rescue WaitReadable Fiber.yield retry end
select fds.each do |fd| call_callback end end end def on_accept c = accept Fiber.new do loop do read_request(c) do_it write_response(c) end end.resume end It Fiber.yields back to main_loop before it I/O blocks Resumes on call back def read_n(fd, sz) ... fd.read_nonblock(sz) rescue WaitReadable Fiber.yield retry end
Bartender::Context Callbacks when readable or writeable Use this to implement block-ish non-block I/O register callbacks for the combination of event types (:read, :write) and fd
fd.read_nonblock(sz) rescue IO::WaitReadable wait_readable(fd) retry end def wait_readable(fd); wait_io(:read, fd); end def wait_io(event, fd) self[event, fd] = Fiber.current.method(:resume) Fiber.yield ensure delete(event, fd) end - read_nonblock. On exception, it waits to be readable before it retries. - Waits to be what? -- We need to context switch to another fiber
rescue IO::WaitReadable wait_readable(fd) retry end def wait_readable(fd); wait_io(:read, fd); end def wait_io(event, fd) self[event, fd] = Fiber.current.method(:resume) Fiber.yield ensure delete(event, fd) end If there are any readable data, it reads and returns - There are cases when it's below sz Excepts when there is no readable data - IO::WaitReadable
rescue IO::WaitReadable wait_readable(fd) retry end def wait_readable(fd); wait_io(:read, fd); end def wait_io(event, fd) self[event, fd] = Fiber.current.method(:resume) Fiber.yield ensure delete(event, fd) end Register resume as callback Fiber.yield - Goes back to mainloop and selects at the end readable when resumed
false) msg = load(reader) argc = load(reader) argv = argc.times.collect {load(reader)} block = load(reader, false) [ref, msg, argv] end def load(reader, marshal=true) sz = reader.read(4) sz = sz.unpack('N')[0] data = reader.read(sz) return data unless marshal begin Marshal.load(data) rescue DRb::DRbUnknown.new($!, data) end end extracted from tiny_drb - Where it constructs with the read messages - Just lining up reads, blocks are ignored - When blocked, it context switches implicitly.
Ol' days (in C) - Call functions that read & construct messages after select() -- Cannot switch tasks when there is latency and/or incident, and freezes
= IO.pipe @task = Thread.new do begin block.call(*args) ensure left.close end end end def value if @right Bartender.wait_readable(@right) @right.close end @task.value ensure @right = nil end end Sync Threads with FD - Stops on Thread.value - Notifies stop with IO.pipe close Skip!
you need to understand everything about the library or you'll get stuck -- If you know that you'll get stuck, you're okay --- (Actually, it doesn't need to be Fiber to get stuck)
- Making a Fiber version of Twitter timeline reading -- JSON.parse reads and puts everything into a string →Won't work - Is there JSON.parse that reads from streams?
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