Modern Programming Concepts in Engineering - Vietnamese ...

Modern Programming Concepts in Engineering
universal machine program specialized machine
Topic 1: Introduction
Matthias Baitsch
Vietnamese-German University

About the course. . .

Goals of the course
After successfully completing this course, you will
◮ know the key concepts of object-oriented programming
◮ master a programming language: Java
◮ be able to tackle many different programming problems in
engineering sciences
◮ know about types of algorithms and you will be able to
implement them
◮ know a variety of data structures and you will choose the right
one for your problem at hand
◮ build your own software upon existing libraries

What other students programmed after one semester Java
Simulation of a nonlinear pendulum
Start application: Mac OS X/Windows

We use an existing software package: view3D
What is the “view3D” package?
◮ Java library for interactive 3D graphics
◮ Based on freely available Visualization Toolkit (VTK)
◮ Developed at the Institute for Computational Engineering

Learning approach: Outside-in
What does outside-in mean?
You start as consumer of software and you will become a producer
of software later on. We will start with the view3D package.
Using the view3D library, you
◮ build three-dimensional models easily
◮ create interesting programs from the first day on
◮ learn from existing software which serves as model and
inspiration
◮ become familiar to the use of software through abstract
interfaces

Why modern programming concepts in engineering?

Why modern programming concepts in engineering?
1. Computing is pervasive in engineering:
◮ Numerical simulations
◮ Optimization of structures and processes
◮ Computer aided design
◮ Environmental modeling
◮ Construction management
◮ Data management
Advances in engineering depend on advances in computing

Why modern programming concepts in engineering?
2. Engineering problems become:
◮ Bigger (in terms of simulation model size)
◮ More complicated (coupled fields, probability, . . . )
◮ Multidisciplinary (take into account engineering aspects,
economics, energy management, . . . )
Industry demands for software solutions

Why modern programming concepts in engineering?
In order to cope with current and future challenges, creators of
engineering software have to
◮ employ efficient solution procedures (numerical methods)
◮ exploit modern computer hardware (parallel computing)
◮ use the Internet (distributed and grid computing)
◮ establish interactive simulation models (computational
steering, virtual reality)
◮ provide comprehensible evaluation methods (visualization)
◮ ensure correctness of results (as far as possible)
Problems can not be solved simply by trial and error, rather a rich
set of methods and concepts is required

What are modern programming concepts in engineering?
Most important methods and concepts:
◮ Object-oriented programming (OOP)
◮ Formal modeling techniques (Unified Modeling Language)
◮ Use of existing software packages, frameworks and services
◮ Automated testing and test driven development
◮ Modern user interfaces and interactive visualization
→ Choice of methods and concepts depend on software project

Why object-oriented programming (OOP)?
Short answer
Because object-oriented programming works!

Why object-oriented programming (OOP)?
Short answer
Because object-oriented programming works!
Long answer
Because object-oriented programming
◮ provides a natural and powerful way to model actual
(engineering) problems
◮ simplifies the development of software which is extensible and
maintainable
◮ lets developers split software up into separate, reusable parts
◮ helps developers to build reliable software systems
◮ simplifies programming in a team of programmers
→ OOP helps to keep complex software systems manageable

Choosing a programming language for MPCE
We use Java because Java is
◮ strictly object-oriented
◮ comparatively easy to learn
◮ a modern programming language
◮ supported by various freely available development
environments
◮ platform independent and programs are portable
We do we not use
◮ Fortran: Not object oriented, limited to numerics
◮ C++: Widely used and powerful but hard to learn
◮ C#: Would be an alternative but proprietary
◮ Visual Basic: Not suitable for numerical computations
Languages in green: Widely used in engineering

The Java Virtual Machine
Compiled language
Java VM
hello.cpp
Source code
hello.java
Source code
C++ compiler
Java compiler
Byte code
Virtual machine
hello.exe
Executable
hello.class
java.exe
◮ Compiler generates machine
code
◮ Machine code is directly
executed by CPU
◮ Compiler generates byte
code
◮ Byte code is executed by
virtual machine a which is
executed by CPU
a Often, VMs are implemented in C

The Java Virtual Machine
Advantages of using a Virtual Machine
◮ VM manages memory (garbage collection)
◮ VM performs extensive runtime error checking
◮ VM handles access to system resources (memory etc.)
◮ A Java program can run on any platform where a virtual
machine is available
Simplifies the development of portable, secure and reliable
software!
Disadvantages
◮ Impact on execution speed
◮ Java needs to be installed on the target computer

Summary
Modern Programming Concepts in Engineering
◮ covers theory and practice of object-oriented programming
◮ uses Java as a programming language, but concepts can be
transferred easily to other languages
◮ covers fundamental data structures, how they work and how
to make use of them
◮ introduces basic algorithms from the field of engineering, both
theoretically (complexity) as well as practically (through
examples)

Programming computers

Computers
Blue Gene at Sandia national labs Linux cluster Bochum Laptop computer Mobile phone
Computers are
◮ coming in very different flavours
◮ becoming faster and more powerful
◮ nowadays everywhere
◮ present in nearly every aspect of daily life
Computers are universal machines executing programs

What do the components of a computers do?
Outside world
Computer
- Humans
- Other computers
- Devices
- Environment
Communication
devices
Monitor
Keyboard/Mouse
Processors
Memories
Network device
Sensor
Processors carry out instructions, send and receive data from
communication devices, store and retrieve data and
programs from memories
Memories store program and data, persistent or temporary
Communication devices connect the computer to the outside
world, present and gather data
Processors are instructed by the program they execute

What is a program?

What is a program?
Examples. . .

Interactive program with graphical user interface
Interactive programs
◮ are started by users by clicking an icon
◮ send and receive data from devices such as monitor, printer,
network card, speakers, hard disk drive
◮ react on user input from mouse and keyboard

Console program
Console programs
◮ are started by users by typing a command
◮ typically do not require user input during execution
◮ most often store results of computation on the hard disk
◮ are common in scientific and high-performance computing

Program running on a server computer
User's computer (yours)
Server computer
http request
Web server
(e.g. apache)
html document
Web browser
Server programs
◮ are started automatically when the computer starts up
◮ run for weeks or months
◮ usually do not require any user interaction
◮ interact with other programs running on another computer

Programs turn computers into specialized machines
universal machine program specialized machine
A computer is a universal machine. When you feed it with a
program, it becomes a specialized machine which can be used to
carry out a specific task.
Examples:
◮ Start Word – Your computer becomes a machine for writing a
letter (for your thesis, you might use something else)
◮ Start Ansys – Your computer becomes a machine for
structural analysis

Program execution
Data
Flow
Monitor
Program
Start of program execution
Keyboard/Mouse
Network device
Sensor
processing
Persistent storage
(HDD)
A program
Program termination
◮ has a well-defined entry point where program execution starts
◮ receives input from communication devices
◮ sends data to communication devices
◮ reads and writes data to persistent storage devices
◮ has one or more conditions which terminate program execution
An executing program is an immaterial machine

Building and running programs
A programmer
writes a
which
Program
a user
runs on
a computer

Building and running programs
A programmer
using
a computer
writes a
which
Program
a user
runs on
a computer

Building and running programs
A programmer
using
a computer
writes a
which
Program
run on
users
their computers

Building and running programs
programmers
using
computers
write a
which
Program
run on
users
their computers

What makes a program a good program?
A good program is
correct: It does what it’s supposed to. This sounds trivial but
do you know any program which never crashes?
extensible: It is easy to change and to add new functionality
readable: The program source code is understandable to
humans!
reusable: Parts of the program can be used later to build other
programs (prevent reinvention of the wheel)
robust: It reacts appropriately to errors
secure: It does not let others misuse your computer

Writing computer programs
Writing programs it tough:
◮ Programs crash
◮ Programs give wrong results
◮ Getting a program right can be really hard
→ As a programmer, you are in charge

Writing computer programs
Writing programs it tough:
◮ Programs crash
◮ Programs give wrong results
◮ Getting a program right can be really hard
→ As a programmer, you are in charge
Writing programs is fun:
◮ Design and build your own machines
◮ Exert your creativity and imagination
◮ Having created a running program is a good feeling
→ There are (nearly) no limits, what you can do

A first example. . .

A first example: Elastic pendulum
Elements:
- circular section d = 0.1
Material:
- E = 500000 N/m², ρ = 10 kg/m³
Node at (0.0, 2.5)
Node at (2.5, 2.5)
Node at (0, 0)
y
x
Constraint
g = 9.81 m/s²
Next slide: Use existing Java package (miniFE – developed in
Bochum) in order to create a finite-element model of the system
and to perform a nonlinear transient analysis simulating 20 seconds
using 2000 timesteps.

import i n f . m i n i f e . f e . Node ;
import i n f . m i n i f e . f e . e l e m e n t s . e1d . Truss2D ;
import i n f . m i n i f e . f e . s c t . C i r c l e S ;
import i n f . m i n i f e . f e . u t i l . A n a l y s i s T y p e s ;
import i n f . m i n i f e . view2 . Viewer2 ;
p u b l i c c l a s s PendulumProgram {
p u b l i c s t a t i c void main ( S t r i n g [ ] a r g s ) {
Model m = new Model ( ) ;
Node n1 = m. createNode ( 0 . 0 , 0 . 0 ) ;
Node n2 = m. createNode ( 2 . 5 , 2 . 5 ) ;
Node n3 = m. createNode ( 0 . 0 , 2 . 5 ) ;
C o n s t r a i n t c = new C o n s t r a i n t ( f a l s e , f a l s e , true ) ;
M a t e r i a l mat = m. c r e a t e M a t e r i a l ( 5 0 0 0 0 0 . 0 , 1 0 . 0 ) ;
C i r c l e S s c t = m. c r e a t e S e c t i o n ( C i r c l e S . TYPE ) ;
n1 . s e t C o n s t r a i n t ( c ) ;
s c t . s e t D i a m e t e r ( 0 . 1 ) ;
m. c r e a t e E l e m e n t ( Truss2D . TYPE, mat , s ct , n1 , n2 ) ;
m. c r e a t e E l e m e n t ( Truss2D . TYPE, mat , s ct , n2 , n3 ) ;
m. g e t S e t t i n g s ( ) . s e t A c c e l e r a t i o n (DOF. T Y , 9 . 8 1 ) ;
A n a l y s i s T y p e s . n o n l i n e a r T r a n s i e n t (m, 2 0 , 2 0 0 0 , 1 e − 6 , 0 . 7 ) ;

The running program

Summary
◮ Today, engineering and computing are closely connected
◮ Computers are universal machines
◮ Feeding a computer with a program turns the computer into a
specialized machine
◮ An executing program is an immaterial machine
◮ Object-oriented software models can be close to the problem
domain
◮ Existing libraries can provide powerful functionality