Threads and Classes

[Charles Pegge]

If classes contain static members then, as a general rule, they cannot be used by more than one thread at a time. The simplest solution is to create separate classes for each thread.

In this scheme, each set of classes is recreated within each thread. I have put them inside the thread functions, (though it is not essential to do this; they could be placed immediately before each thread function).

Code: OxygenBasic

1.  
2. 'CLASSES WITH STATIC MEMBERS:
3. 'HOW TO DEPLOY FOR MULTITHREADING
4.  
5. macro InclStatClasses()
6.   '
7.  class CA
8.     static sys s
9.     sys a
10.     method m(sys n)
11.       print "CA ok: " n
12.     end method
13.   end class
14.   '
15.  class CB
16.     static sys s
17.     sys a
18.     method m(sys n)
19.       print "CB ok: " n
20.     end method
21.   end class
22.   '
23. end macro
24.  
25. function thread1(sys n) external
26.   InclStatClasses
27.   CA c
28.   c.m n
29.   #recordof CA
30. end function
31.  
32. function thread2(sys n) external
33.   InclStatClasses
34.   CA c
35.   c.m n
36.   #recordof CA
37. end function
38.  
39. 'CHECK EACH THREAD ALONE
40.  
41. thread1 1
42. thread2 2
43.  
44.  

Charles

[kryton9]

Thanks Charles, can't wait to test later tonight and get used to using threads. I need to feel comfortable with them if I am serious about a game engine.

[Charles Pegge]

The next aspect is to establish a simple communication sytem so that threads can communicate with the controller and the other threads.

In this example,  a table is used to send and receive integer messages. There is a separate cell for each communication, so there is no possibility of conflicting signals.

One point to note is that the '%' equates are expanded late.

Code: OxygenBasic

1.  
2. 'CALLS FOR MULTITHREADING ETC
3.  
4. library "kernel32.dll"
5. sys   CreateThread (sys lpThreadAttributes, dwStackSize, lpStartAddress, lpParameter, dwCreationFlags, *lpThreadId)
6. dword WaitForMultipleObjects(sys nCount,*lpHandles, bWaitAll, dwMilliseconds)
7. bool  CloseHandle(sys hObject)
8. void  Sleep(sys dwMilliSeconds)
9. library ""
10.  
11. % INFINITE 0xFFFFFFFF  'Infinite timeout
12.  
13.  
14. 'COMMUNICATION SYSTEM
15. '====================
16.  
17. indexbase 1
18.  
19. % Threads          16 'including controller
20. % MsgNone          0
21. % MsgSlow          1
22. % MsgFast          2
23. % MsgHello         42
24. % MsgTerminate     255
25. '
26. % MsgFromCtrler    n*threads
27. % MsgFromA         n*threads+1
28. % MsgFromB         n*threads+2
29. '...
30. % MsgToCtrler      n
31. % MsgToA           1*threads+n
32. % MsgToB           2*threads+n
33. '...
34.  
35.  
36. sys signal[threads*threads] 'communications table
37.  
38.  
39. 'THREAD FUNCTIONS
40.  
41. function threadA(n) external
42. finit
43. do
44.   if signal[MsgFromCtrler]=MsgTerminate then exit do
45.   signal[MsgToCtrler]=MsgHello
46.   sleep 1
47. end do
48. print "A terminated " n
49. end function
50.  
51. function threadB(n) external
52. finit
53. do
54.   if signal[MsgFromCtrler]=MsgTerminate then exit do
55.   signal[MsgToCtrler]=MsgHello
56.   sleep 1
57. end do
58. print "B terminated " n
59. end function
60.  
61. sys Funs[threads]={@threadA,@threadB}, ThreadsRunning=2
62.  
63. 'START THREADS
64.  
65. sys  hThread[threads], id[threads], i, n
66. '
67. for i=1 to threadsRunning
68.   hThread[ i ] =  CreateThread 0,0,funs[ i ],i,0,id[ i ]
69. next
70.  
71.  
72. 'CHECK FOR HELLO MESSAGES
73.  
74. sleep 10 'wait for threads to activate
75.  
76. print "Running: " signal[MsgFromA] "," signal[MsgFromB]
77.  
78.  
79. 'END THREADS
80.  
81. signal[MsgToA]=MsgTerminate
82. signal[MsgToB]=MsgTerminate
83.  
84. WaitForMultipleObjects ThreadsRunning, hThread, 1, INFINITE
85.  
86. for i=1 to ThreadsRunning
87.   CloseHandle hThread[ i ]
88. next
89.  
90.  

Charles