FreeBASIC CondBroadcast

'' すべてのスレッドが、コードの連続セクションの実行を続行する前に、
'' どのようにすれば互いを待機できるのでしょうか?
''
'' これは、コードの同時セクションの同期を管理するメイン コードです。:
''    - Each thread signals to main code that it is waiting for synchronization.
''    - The main code waits for each of all threads, then sends the synchronization signal to all threads.
''
'' The synchronization uses the following keywords from threading:
''   - In each thread : 'Condsignal' (to send signal to main code) then 'Condwait' (to wait signal from main code).
''   - In main code : 'Condwait' (to wait signal from each thread) then 'Condbroadcast' (to send signal to all threads).
'' With the associated mutexes and conditional variables and flags.
''
'' すべてのスレッドを同期させて、対応するコードセクションを実行するときの、スレッドの構造とその動作を強調したテスト例 :

Dim threadnumber As Integer = 4

'' global data for all threads
    Dim Shared restart As Integer = 0
    Dim Shared threadcount As Integer = 0
   
    Dim Shared hmutexrestart As Any Ptr
    Dim Shared hcondrestart As Any Ptr
    Dim Shared hmutexready As Any Ptr
    Dim Shared hcondready As Any Ptr

Sub mythread(ByVal p As Any Ptr)
   
    Dim id As Integer = Cast(Integer, p)
   
    '' for visualizing thread status
        Print "   Thread #" & id & " is started..."
       
    '' instead of starting user code
        Sleep id * 40, 1
       
    '' for visualizing thread status
        Print "      Thread #" & id & " is running..."
        Sleep id * 20, 1  '' just to well visualize thread interlacing
        Print "   Thread #" & id & " is waiting for synchronization..."
       
    '' for sending signal to main code
        MutexLock hmutexready
            threadcount += 1
            CondSignal hcondready
        MutexUnlock hmutexready
       
    '' for waiting signal from main code
        MutexLock hmutexrestart
            Do While restart = 0  
                CondWait hcondrestart, hmutexrestart
            Loop
        MutexUnlock hmutexrestart
       
    '' for visualizing thread status
        Print "   Thread #" & id & " is reactivated..."
       
    '' instead of synchronized user code
        Sleep id * 40, 1
       
    '' for visualizing thread status
        Print "      Thread #" & id & " is continuing..."
        Sleep id * 20, 1  '' just to well visualize thread interlacing
        Print "   Thread #" & id & " is finishing execution..."
   
End Sub


Dim threads(1 To threadnumber) As Any Ptr

hcondrestart = CondCreate()
hmutexrestart = MutexCreate()
hcondready = CondCreate()
hmutexready = MutexCreate()

'' for visualizing main code status
    Print "Start all threads from main code :"
       
'' for starting all threads
    For i As Integer = 1 To threadnumber
        threads(i) = ThreadCreate(@mythread, Cast(Any Ptr, i))
    Next i

'' for waiting for all threads waiting for synchronisation
    MutexLock hmutexready
        Do Until threadcount = threadnumber
            CondWait(hcondready, hmutexready)
        Loop
    MutexUnlock hmutexready

'' for visualizing main code status
    Print "All thread seen waiting from main code"
           
    Print
    Print "Reactivate all threads from main code :"
       
'' for reactivating all threads
    MutexLock hmutexrestart
        restart = 1
        CondBroadcast hcondrestart
    MutexUnlock hmutexrestart

'' for waiting for all threads to be completed
    For i As Integer = 1 To threadnumber
        If threads(i) <> 0 Then
            ThreadWait threads(i)
        End If
    Next i
   
'' for visualizing main code status
    Print "All thread seen completed from main code"

MutexDestroy hmutexready
CondDestroy hcondready
MutexDestroy hmutexrestart
CondDestroy hcondrestart

Sleep