Figure 1: Intertwined output of three threads.

Primary thread terminating
t1: i =          0
t1: i =     200000
t1: i =     400000
t1: i =     600000
t2: i =   -1000000
t2: i =    -800000
t2: i =    -600000
t2: i =    -400000
t2: i =    -200000
t2: i =          0
t2 thread terminating
t1: i =     800000
t1: i =    1000000
t1 thread terminating