Option TargetCPU ZX24e
Option TaskStackMargin 2
Option Ramsize 64*1024-Register.RamStart

#define TASK_STACK_SIZE	29
#define MAIN_STACK_SIZE	51
#define HEAP_OVERHEAD	2


Sub Main()
	Dim i as UnsignedInteger, stack as UnsignedInteger, numberTasks as UnsignedInteger
	Dim counters as UnsignedInteger, counterAddr as UnsignedInteger
	Dim previousTime as Single, currentTime as Single
	Dim totalCount as Long
		
	' Calculate number of tasks from available RAM
	numberTasks = (Register.RAMSIZE - MAIN_STACK_SIZE - HEAP_OVERHEAD) \ (TASK_STACK_SIZE + SIZEOF(Byte) + HEAP_OVERHEAD)
	
	' use one less as seems to cause error with devices with extended RAM
	numberTasks = numberTasks - 1
	
	' For extended RAM, need to allocate one less task
	Debug.Print "Available RAM is "; CStr(Register.RAMSIZE); " so number of tasks is " ; CStr(numberTasks)

	' allocate space on heap for task counters
	' seems to need one extra byte at the end of the heap so add 1 to be safe
	counters = System.Alloc(numberTasks * SIZEOF(Byte))
	If counters = 0 Then
		Debug.Print "Failed to allocate RAM for task counters"
		Exit Sub
	End If	
	
	Debug.Print "Creating "; CStr(numberTasks); " tasks:"
	previousTime = Timer()
	
	' Lock main task while we create the other tasks.
	' This prevents too much slowdown during task creation.
	Call LockTask()
	
	For i = 0 to numberTasks-1
		' calculate address of this counter
		counterAddr = counters + i * SIZEOF(Byte)
		' reset the counter for each task
		Call RAMPoke(0, counterAddr)
		
		' this allocates memory off the heap for each task stack
		stack = System.Alloc(TASK_STACK_SIZE)
		If stack <> 0 Then
			' create the task and add it to the rubnnable task list but it wont run yet
			'Debug.Print "Task "; CStr(i); ": stack at address "; CStr(stack); " and counter at address "; CStr(counterAddr)
			CallTask Task(CByteArray(counterAddr)), stack, TASK_STACK_SIZE
			
			' print a period and the task number every 100 tasks
			Debug.Print ".";
			If ((i+1) Mod 100) = 0 Then
				Debug.Print CStr(i+1)
			End If
		Else
			Debug.Print "Could not create task "; CStr(i)
		End If
	Next
	Debug.Print
	
	' print how it took to create the tasks
	currentTime = Timer
	Debug.Print "Elapsed time is "; CStr(currentTime - previousTime); " seconds"
	previousTime = currentTime
	
	' We can unlock main at this point. If it's time slice is about to end then another
	' task may be able to run
	Call UnlockTask()

	' Loop forever, monitoring the task counters
	Do
		' We need to lock the main task to give it time to print the counter information
		Call LockTask()
		currentTime = Timer
		Debug.Print
		Debug.Print "***** Elapsed time is "; CStr(currentTime - previousTime); " seconds"
		previousTime = currentTime
		totalCount = 0
		' Calculate the sum of all of counters and then print out the mean
		totalCount = 0
		For i = 0 to numberTasks-1
			' calculate address of this counter
			counterAddr = counters + i * SIZEOF(Byte)
			
			' add on this counter
			'Debug.Print CStr(RAMPeek(counterAddr)); " ";
			totalCount = totalCount + CLng(RAMPeek(counterAddr))
		Next
		Debug.Print "Average count is "; CStr(CSng(totalCount)/CSng(numberTasks))
		Call UnlockTask()
		
		' At this point, the next runnable task gets a chance to execute
		Call Sleep(5.0)
	Loop
End Sub

' This is the simple task that increments a counter. The counter is only a byte
' so it will wrap every 256 counts
Public Sub Task(ByRef counterMemory() as Byte)
	Dim counter as Byte Alias counterMemory
	Do
		counter = counter + 1
		' Give some other task a chance after one increment
		Call Sleep(0)
	Loop
End Sub