Современные информационные технологии/3. Программное обеспечение

Zhuaspaev T.A

A.Baitursynov Kostanai State University, Kazakhstan

USING MULTIPLE STREAMS WITH CLASS TTHREAD In C + +

In some cases, the application should organize the work of 2 or more concurrent threads. This need arises when unrelated data blocks, the more computation that does not require sequential location in the program code. For example, one thread of execution can perform most of the work, and the second, with a lower priority may at the same time to prepare some files that will be needed in the future, ie perform the dirty work. Another example - the parallel operation with multiple external sources of information. Especially large gains in productivity through parallel execution of multiple threads can be obtained in a multiprocessor system in which you can organize the implementation of each strand of a single processor. Class TThread - an abstract class that allows you to create a separate thread in the application of the [1].

To study the TThread programming environment used by Borland C + + Builder 6.0.

The threads used in a variety of independent calculations, but they can be used in more complex calculations require the use of a single thread of the other results. The easiest way is awaiting the completion of the thread (the method WaitFor ()), and therefore virtually ineffective. Another method is to use a queue. When one thread (receiver) need new data, the preparation of which is engaged in the second (spring), and it is waiting for the completion of the third (the mediator), the latter examines the new data in the queue and returns them if they are.

After a third stream (mediator) is produced, and adding new information to the queue. This is to avoid conflicts of simultaneous use of the queue. The model turn is shown in Picture 1.

Picture 1. The scheme of turn

To create a thread of the existing class that inherits TThread, creates a pointer to the type of this class, and the function returns a pointer to the new object of that class.

NameThreadClass * Potok;

……………

Potok = new NameThreadClass(false);

False parameter indicates immediate execution threads (the function Execute ()) immediately after the constructor (NameThreadClass ()), and the parameter to true will only call the constructor, then the thread is done by Resume (), which in addition to this case is used after the suspension of the thread method Suspend ().

On the basis of the material has been modified 2 applications:

1. Application using a thread.

2. An application that uses three streams, by starting with a queue.

This application of the existing sequence numbers removes the longest sequence of numbers arranged in ascending order. Down stream implements output sequence after the removal, but the task can not be completed before the next two streams. Therefore, from the first stream and a second stream is called waiting for its completion. The second stream adds a numeric sequence in turn and look for the position of the beginning of the longest sequence of numbers arranged in ascending order. Next, the thread returns to the first thread is called from a third stream implements the removal of the sequence length. After the completion of the third stream the result is displayed on the screen (Picture 2).

Picture 2. The resulting output

Literature

1. Архангельский А.Я. Программирование в C++ Builder 6.0 – М.: Бином, 2000 – 1548с

2. Бобровский В.П. Самоучитель программирования на языке С++ в системе Borland C++ Builder 5.0 – М.: Десс, 2000 – 272с