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Threads[Mutex]

  

Create

  

create a new mutex

 

Calling Sequence

Description

Examples

Calling Sequence

Create()

Description

• 

The Create command is used to create a new Mutex.  This command returns an integer identifier that is used to represent the mutex.

• 

The Create command does not accept any arguments.

• 

Once created, the mutex can be locked and unlocked using the Lock and Unlock commands.

• 

When a mutex is no longer needed, it should be destroyed using the Destroy command.  This will release all the resources used by the mutex.

• 

For more information on using mutexes, see the Mutex help page.

Examples

p := proc( m )
   global count;
   print( count );
   count := count+1;
end proc;

p:=procmglobalcount;printcount;count:=count+1end proc

(1)

count1

count:=1

(2)

Create ten threads running the p function.

Threads[Wait]seqThreads[Create]pm,i=1..10

1

2

3

4

5

6

6

8

8

10

(3)

Without mutexes the same value may be printed multiple times.  (You may have to execute this command multiple times to see this occur.)

p := proc( m )
   global count;
   Threads[Mutex][Lock]( m );

   print( count );
   count := count+1;

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

p:=procmglobalcount;Threads[Mutex][Lock]m;printcount;count:=count+1;Threads[Mutex][Unlock]mend proc

(4)

count1

count:=1

(5)

mThreads[Mutex][Create]

m:=1

(6)

Create ten threads running the new p function.

Threads[Wait]seqThreads[Create]pm,i=1..10:

1

2

3

4

5

6

7

8

9

10

(7)

Using a mutex allows you to control access to the shared variable.  Thus each number will be printed only once.

Threads[Mutex][Destroy]m

See Also

Threads

Threads[Create]

Threads[Mutex]

Threads[Mutex][Destroy]

Threads[Mutex][Lock]

Threads[Mutex][Unlock]

 


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