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L E S S O N 5

Supercomputer

Слова и словосочетания для запоминания

break v - прерывать, останавливать

bundle up v – связать

come up with v – внести

follow v – контролировать

impact n- влияние

remote procedure call - дистанционный вызов процедуры

run v – выполнить

subroutine n – подпрограмма

turnaround a - оборотный

TEXT A

Implementing a Distributed Process between Workstation and Supercomputer

Distributed processing seems to have become one of the latest high tech terms that members of the computer society all seem to be using, but perhaps not really understanding. It is desirable to come up with a simple definition of distributed processing.

A software product which takes advantage of more than one computer system in order to produce a result

There are two main reasons of why a distributed process is desirable: time and money.

Tasks that take a long time to compute are the most painful for the user, and these are the tasks that must be optimized for speed. Communication and communications time may be a very large factor against distributed processing. For many cases, the communication time can be significantly greater than the computational time., thus creating an environment in which distributed processing does not seem to be practical or desirable

Communications is the fundemental component in any distributed application. The development of extremely large networking systems has complicated the task of creating distributed applications. The goal of any good communications service or system must be to provide both the user and the application developer with an environment for communications in which all the most fundemental aspects of establishing and maintaining a connection are cared for transparently.

The socket is the basic building block out of which all distributed applications are constructed using TCP. A socket provides a bidirectional stream of communications between two programs runnig on different machines. Data to be sent into one end of a socket appears at the other end within the remotely running program. TCP uses a client/server style of relationship between programs The client program initiates communications by requesting a connection with a particular program runnig on a specific machine. It is the duty of the server program to accept connection requests from client programs. This leads to the notion of the server process as one which provides a particular service and the client process as one requiring it.

The use of TCP at the socket level has an impact on the structure of a distributed application. All data transfer between the different pieces of a distributed code must be done using the read/write style interface Often times it is easier to distribute an application by looking for subroutines which could be run on a remote machine. Particularly in the case of distributing an already existing code, breaking code out at the subroutine level is far simplier than restructuring the code to make us use of the straight socket form of connection. There are several packages available to aid the developer in performing task distribution at the subroutine level, the most notable of these is RPC (remote procedure call).. The subroutine which was removed from the application is moved into a server program along with other subroutines which are to be distributed. The server program, which is run on a remote system, waits for processing requests from the running application. When a request is received, the proper subroutine is called along with the passed parameters, Upon returning, the output parameters are bundled up and send back to the calling program.

MPGS is a multipurpose graphics post processing system which runs on a graphics workstation, and distribute cpu and memory intensive tasks to a Cray supercomputer

The user begins a MPGS session by starting the workstation side of MPGS, followed by the Cray side. The Cray side of MPGS will ask for the network address of the station, and then establishes the communication connection. Next, the user requests MPGS to read the data to be post processed. The Cray side of MPGS will read the data and then download visible portions of the data to the workstation. Down loading only a portion of the data to the workstation, i.e. the visible portions of the data is a very important aspects of minimizing network traffic, and is vital to the success of MPGS.

  1. What is distributed processing?

  2. In what cases is distributed processing practical?

  3. What is the function of a socket?

  4. How does MPGS minimize network traffic?

Упражнение

Переведите предложения, обращая внимание на функции инфинитива

l. Our task is to get good results.2.The RTK Computer Network is likely to provide a model for how to make public information electronically accessible.3 We know the first central electric stations to have been built for supply of electric lights.4.Experimental data to be presented in detail will be discussed as soon as possible. 5.Serious efforts is now being made to overcome the difficulty.6.This process is unlikely to take place 7.To summarize the findings of this tremendous work would require many pages 8 Microchips have allowed computers to evolve from room-sized to notebook- and palm-sized devices.9 No line is to be seen when its intensity is predicted to be zero. l0. This modification of the method appears to be of great value.

TEXT В