The Wait command is called to pause the current thread until it is signaled by the condition variable condId.  The Wait command accepts a mutex identifier as mutexId.  The current thread must have obtained the lock on mutexId by calling the Threads[Mutex][Lock] command. When Wait is called, the thread is paused and mutexId is unlocked atomically.  When the thread is started again, it will re-obtain the lock on mutexId before the thread returns from Wait. Another thread can use the Signal or Broadcast commands with condId as the argument to restart a waiting thread. The Signal and Broadcast commands do not require having mutexId locked, however it is often a good idea to do so.  By locking mutexId while calling Signal or Broadcast you can guarantee that no threads are entering Wait at the same time.

For more information on using condition variables, see the Condition Variable help page.

Producer := proc( m, cp, cc, max, mindiff )
    global tab, e;
    local i,j,n;

    Threads[Mutex][Lock]( m );
    j := 0;

    tab[ "maxjob" ] := mindiff;
    tab[ "curjob" ] := 1;

    for j from 1 to mindiff
    do
        tab[ j ] := 2*j;
    end do;

    Threads[ConditionVariable][Signal]( cp );

    n := false;
    while ( e )
    do
        j := tab[ "maxjob" ];
        if ( j - tab[ "curjob" ] > mindiff/2 ) then
            n := true;
            Threads[ConditionVariable][Wait]( cp, m );
        end if;

        for i from j to tab[ "curjob" ] + mindiff
        do
            tab[ i ] := 2*i;
        end do;

        tab[ "maxjob" ] := tab[ "curjob" ] + mindiff;

        if ( n ) then
            Threads[ConditionVariable][Broadcast]( cc );
            n := false;
        end if;

    end do;
    Threads[Mutex][Unlock]( m );

end proc:
Consumer := proc( m, cp, cc, max )
    global tab, e;
    local n, i, j, num;

    num := 0;
    Threads[Mutex][Lock]( m );
    while ( num < max )
    do
        while ( tab[ "curjob" ] = tab[ "maxjob" ] )
        do
            Threads[ConditionVariable][Signal]( cp );
            Threads[ConditionVariable][Wait]( cc, m );
        end do;

        n := tab[ "curjob" ];
        j := tab[ n ];
        tab[ "curjob" ] := n + 1;

        Threads[Mutex][Unlock]( m );

        j := add( i, i=1..j );
        num := num+1;

        Threads[Mutex][Lock]( m );
        tab[ n ] := j;
    end do;
    Threads[Mutex][Unlock]( m );
end proc:

$\mathrm{tab}≔\mathrm{table}\left(\right)\&colon;$

$m≔\mathrm{Threads}\left[\mathrm{Mutex}\right]\left[\mathrm{Create}\right]\left(\right)$

$m≔2$

$\mathrm{cc}≔\mathrm{Threads}\left[\mathrm{ConditionVariable}\right]\left[\mathrm{Create}\right]\left(\right)$

$\mathrm{cc}≔1$

$\mathrm{cp}≔\mathrm{Threads}\left[\mathrm{ConditionVariable}\right]\left[\mathrm{Create}\right]\left(\right)$

$\mathrm{cp}≔2$

$e≔\mathrm{true}\&colon;$

$\mathrm{Threads}\left[\mathrm{Mutex}\right]\left[\mathrm{Lock}\right]\left(m\right)$

$\mathrm{id1}≔\mathrm{Threads}\left[\mathrm{Create}\right]\left(\mathrm{Producer}\left(m\&comma;\mathrm{cp}\&comma;\mathrm{cc}\&comma;31\&comma;10\right)\right)$

$\mathrm{id1}≔1$

$\mathrm{Threads}\left[\mathrm{ConditionVariable}\right]\left[\mathrm{Wait}\right]\left(\mathrm{cp}\&comma;m\right)$

$\mathrm{Threads}\left[\mathrm{Mutex}\right]\left[\mathrm{Unlock}\right]\left(m\right)$

$\mathrm{id2}≔\left[\mathrm{seq}\left(\mathrm{Threads}\left[\mathrm{Create}\right]\left(\mathrm{Consumer}\left(m\&comma;\mathrm{cp}\&comma;\mathrm{cc}\&comma;100\right)\right)\&comma;i=1..5\right)\right]$

$\mathrm{id2}≔\left[2\&comma;3\&comma;4\&comma;5\&comma;6\right]$

$\mathrm{Threads}\left[\mathrm{Wait}\right]\left(\mathrm{op}\left(\mathrm{id2}\right)\right)$

$\mathrm{Threads}\left[\mathrm{Mutex}\right]\left[\mathrm{Lock}\right]\left(m\right)$

$e≔\mathrm{false}\&colon;$

$\mathrm{Threads}\left[\mathrm{ConditionVariable}\right]\left[\mathrm{Signal}\right]\left(\mathrm{cp}\right)$

$\mathrm{Threads}\left[\mathrm{Mutex}\right]\left[\mathrm{Unlock}\right]\left(m\right)$

$\mathrm{Threads}\left[\mathrm{Wait}\right]\left(\mathrm{id1}\right)$

$\mathrm{print}\left(\mathrm{tab}\left[''curjob''\right]\right)$

$501$

$\mathrm{print}\left(\mathrm{tab}\left[233\right]\right)$

$108811$

$\mathrm{print}\left(\mathrm{add}\left(i\&comma;i=1..2\cdot 233\right)\right)$

$108811$