Does BMax have multithreading yet?

BlitzMax Forums/BlitzMax Programming/Does BMax have multithreading yet?

Scienthsine (Posted 2009) [#1]

Gah, searches come up with all the old topics about it. I saw that the new garbage collector is threaded... so can someone clue me in? I haven't been around in a while... so kinda lost.

plash (Posted 2009) [#2]

Yes... it does.

Scienthsine (Posted 2009) [#3]

So how does it work? Can you spawn threads from blitz code directly, or is it just thread safe? Is there any kind of documentation I can look at?

plash (Posted 2009) [#4]

Taken (and modified a bit) from 'blitzmax/samples/threads/threads.bmx': ' ----------------------------------------------------------------------------- ' Simple thread demo... ' ----------------------------------------------------------------------------- SuperStrict Framework brl.blitz Import brl.threads Import brl.standardio ' Mutexes are used to allow only one thread to access a variable or object in ' memory. ' A thread (including the main program's thread) can call LockMutex ' on a mutex, and if another thread has already locked the mutex, it will ' wait until the other thread has unlocked the mutex, then gain the lock. It's ' important that a thread calls UnlockMutex when it's done what it needs to do! ' The main program's thread and the spawned thread will both attempt to lock ' this mutex throughout, waiting on each other if they can't lock it... Global Mutex:TMutex = CreateMutex() ' Try commenting out the above line, then scroll back through the output of ' the program, and you should see that the threads are fighting for access to ' the output console, creating intermeshing, gibberish text... Print("") Print("NOTE: Output of the two threads may not always alternate between 'Main' and 'Thread'...") Print("") ' Create thread using Test() function and pass Null parameter... Local thread:TThread = CreateThread(Test, Null) ' The new thread has now started. Do some stuff in the main program... For Local a:Int = 1 To 100 ' Other thread may be using the Print command (which isn't thread-friendly), ' so LockMutex will wait until the thread has unlocked the mutex, and then ' lock it so main program can call Print. It will then unlock the mutex so ' the other thread can continue if it's ready (ie. waiting at its own ' LockThread call)... If Mutex Then LockMutex(Mutex) Print("Main: " + a) If Mutex Then UnlockMutex(Mutex) ' Note: You'd normally just do this like the Rem'd out code below! The ' "If Mutex" check here is to allow you to comment out the line ' "Global Mutex = CreateMutex ()" to see why mutexes are needed... ' You would also not normally use LockMutex so heavily, as it will ' slow things down if over-used... Rem LockMutex(Mutex) Print("Main: " + a) UnlockMutex(Mutex) End Rem Next ' Other thread may still be running, so wait for it to end... WaitThread(thread) End ' ----------------------------------------------------------------------------- ' Test function. Locks same mutex as main program, or waits until it ' can do so, calls Print, then unlocks the mutex so main program can ' lock it and proceed... ' ----------------------------------------------------------------------------- Function Test:Object(data:Object) For Local a:Int = 1 To 100 If Mutex Then LockMutex(Mutex) Print("--------> Thread: " + a) If Mutex Then UnlockMutex(Mutex) Next End Function

Scienthsine (Posted 2009) [#5]

Alright! I've been in the electronics world for a while... but maybe it's time to dust off BMax for a bit of playing around with! Thanks Plash, exactly what I was wanting to know.

K@li (Posted 2009) [#6]

Global Mutex:TMutex = CreateMutex() error : Tmutex not found !!

BlitzSupport (Posted 2009) [#7]

K@li: Turn on Program menu -> Build Options -> Threaded Build. Make sure you're using the latest BlitzMax release too!

K@li (Posted 2009) [#8]

Great !! thanks....

Scienthsine (Posted 2009) [#9]

Ok, so there's decent documentation on threads, mutexes, and semophores, but nothing really about CondVars and a few new functions: AtomicAdd and AtomicSwap. Do these two work on variables without the need to use a mutex?