fibers.md Fibers ====== A[Fiber](@refSpicyPixel.Threading.Fiber)isalightweightmeansofschedulingworkthatenablesmultipleunitsofprocessingtoexecuteconcurrentlybyco-operativelysharingexecutiontimeonasinglethread.Fibersarealsoknownas"micro-threads"andcanbeimplementedusingprogramminglanguagefacilitiessuchas"coroutines". Fiberssimplifymanyconcurrencyissuesgenerallyassociatedwithmultithreadingbecauseagivenfiberhascompletecontroloverwhenityieldsexecutiontoanotherfiber.Afiberdoesnotneedtomanageresourcelockingorhandlechangingdatainthesamewayasathreaddoesbecauseaccesstoaresourceisneverpreemptedbyanotherfiberwithoutco-operation. Fiberscanimproveperformanceincertainapplicationswithconcurrencyrequirements.Becausemanyfiberscanrunonathread,thiscanrelievepressureonpreciousresourcesinthethreadpoolandreducelatency. Additionally,someapplicationshaveconcurrent,interdependentprocessesthatnaturallylendthemselvestoco-operativeschedulingwhichcanresultingreaterefficiencywhentheapplicationmanagesthecontextswitchinsteadofapre-emptivescheduler. Fiberscanalsobeaconvenientwaytoexpressastatemachine.Themasterfiberimplementingthemachinecanteststateconditions,startnewfibersforstateactions,yieldtoanactionfiberuntilitcompletes,andthenhandlethetransitionoutofthestateandintoanewstate. Startingafiber ---------------- Afibercanbecreatedandstartedonthedefaultschedulerforthethreadasfollows. ```{.cs} Fiber.StartNew(()=>DoTask()); ``` Itisalsopossibletomorepreciselycontrolstartupandscheduleroptions. ```{.cs} varfiber=newFiber(()=>DoTask());//createthefiber fiber.Start(myCustomScheduler);//queueforexecutionbyacustomscheduler ``` Usingcoroutines ---------------- Acoroutineisafunctionthatcanyieldexecutiontoanotherfunctionandthisallowsmultiplefunctionstoexecuteconcurrentlyonthesamethreadbyco-operativelyyieldingexecutiontime. CoroutinesmustreturnanIEnumeratortypeandhaveoneormoreyieldstatementsthatpassesayieldinstructionbacktothefiberscheduler. ```{.cs} voidMain() { Fiber.StartNew(FadeOutCoroutine()); } IEnumeratorFadeOutCoroutine() { vartotalTime=4f; varcurrentTime=totalTime; while(currentTime>0f) { setAlpha(currentTime/totalTime);//fadeout currentTime-=Time.deltaTime; yieldreturnFiberInstruction.YieldToAnyFiber; } } ``` Waitingforcompletion ---------------------- Onefibercanwaitforcompletionofanotherbyyieldingthe[YieldUntilComplete](@refSpicyPixel.Threading.YieldUntilComplete)instructionreturnedby[Start](@refSpicyPixel.Threading.Fiber.Start). ```{.cs} voidMain() { Fiber.StartNew(Fiber1()); } IEnumeratorFiber1() { Console.Out.WriteLine(“BeginningFiber1andwaitingforFiber2tocomplete”); yieldreturnFiber.StartNew(Fiber2()); Console.Out.WriteLine(“Fiber2hascompleted.); } IEnumeratorFiber2() { //Dowork while(!workDone) { Process(); yieldreturnFiberInstruction.YieldToAnyFiber; } } ``` Startingafiberscheduler -------------------------- Fibercoordinationandexecutionishandledbya[FiberScheduler](@refSpicyPixel.Threading.FiberScheduler).Thedefaultsystemschedulercanbestartedontherunningthreadasfollows. ```{.cs} voidMain() { FiberScheduler.Current.Run(newFiber(MainFiber())); } IEnumeratorMainFiber() { //dowork } ``` Startingafiberscheduleronanewthread ------------------------------------------ Itisoftenmoreconvenienttostartafiberscheduleronanewthread.The[SystemFiberScheduler](@refSpicyPixel.Threading.SystemFiberScheduler)hasconveniencemethodstocreatethescheduleronanewthreadandreturnareference. ```{.cs} voidMain() { varscheduler=SystemFiberScheduler.StartNew(newFiber(MainFiber())); } IEnumeratorMainFiber() { //dowork } ```