21.2 Threads

A new concurrent thread in Oz is created by using the expression of the form thread ... end. For instance, during the execution of the following program two threads proceed concurrently:

declare 
X {Browse X}
thread {Wait X} end 
X = 1

Synchronization of threads is supported in Oz on the basis of logic variables. This is illustrated by the following program whose execution again needs two threads (compare chapter 8 of Seif Haridi's tutorial on Oz which you can find at http://mozart.ps.uni-sb.de/documentation/tutorial/node8.html#chapter.concurrency).

declare X0 X1 X2 X3 in  
{Browse [X0 X1 X2 X3]}
thread  
   local Y0 Y1 Y2 Y3 in  
      {Browse [Y0 Y1 Y2 Y3]}   
      Y0 = X0+1
      Y1 = X1+Y0
      Y2 = X2+Y1
      Y3 = X3+Y2
      {Browse completed}
   end  
end  
X0 = 0
X1 = 1
X2 = 2
X3 = 3

If you would like to observe the two threads in the execution you might be willing to use the Oz-debugger called Oscar which is available form the Mozart user interface (below the menue entry Oz).