CSCE 206 Scientific Applications Programming

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CSCE 206Scientific Applications Programming

• This is not a course in programming
• This is a course in computing
• We will do a lot of programming
• It will at times seem like a course in
  programming, because we will sometimes get bogged
  down in details

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CSCE 206

• This will at times seem like a course in
  programming, because we will sometimes get bogged
  down in details
• Try to remember
• that this is a course in computing
• that to know computing you must know
  programming
• that our goal is computing for numerical
  applications

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Numerical Applications

• Top 500 list www.top500.org
• Finding roots of equations
• Interpolation of functions
• Curve fitting
• Numerical differentiation
• Numerical integration
• Matrix operations
• Averages, deviations, moments
• Differential equations

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Why Fortran?

• Why not Matlab? MathCad? Maple? Mathematica?
• For small applications, these are fine
• For large applications, they are too slow and
  inflexible
• Real computing requires a real language

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Which Fortran?

• 195x FORTRAN
• 1962 FORTRAN II
• 1966 FORTRAN IV (a.k.a. FORTRAN 66)
• 1977 FORTRAN 77
• 1990 Fortran 90
• 1995 Fortran 95
• 2003 Fortran 2000 a.k.a. Fortran 2k
• Various other versions have also existed (HPF,
  IBM FORTRAN G, H, )

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Which Fortran?

• The big change was to Fortran 90 from FORTRAN 77
• We will do F90, which is the modern Fortran
• Differences between F90, F95, and F2K are
  nonexistent at the level of this course
• Vendors have always enhanced their languages as
  a way of making vendor switching hard
• We will concentrate on ANSI Standard Fortran 90
• (ANSI American National Standards Institute)

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Why Unix?

• For small jobs, for simple experimentation, you
  should use Matlab, or something similar.
• The reason for using a real programming language
  is to solve problems too big for desktops.
• There arent any non-Unix machines on the Top 500
  list (and I dont think there ever have been
  any).
• Real computing is done on Unix machines.

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Which Unix?

• It is almost true that all Unix is alike.
• Unix
• Linux
• Solaris (Sun Microsystems)
• HPIX (Hewlett-Packard)
• Irix (Silicon Graphics)
• UNICOS (Cray Research, Inc.)
• AIX (IBM)

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Why Unix?

• I view different computer operating systems as
  being like different cuisines. Using an Apple is
  like keeping kosher the believers would not live
  any other way, but they cannot eat with members
  of other religions. Using Unix is like preparing
  your own meals from recipes in the Joy of
  Cooking the effort involved initially exceeds
  the palatability of the results, but experience
  eventually brings satisfaction. Using Microsoft
  Windows is like eating at a McDonalds you can
  find one anywhere, and the food will keep you
  going, but it would be sad if there were no other
  restaurant in town.
• (Gerald Folland, American Math Monthly, March
  2000)

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Bottom Line

• We will, therefore, cover
• computing
• in the modern (standard) version of Fortran
• on numerical applications
• on a standard Unix platform
• This will be computing done the way its done in
  the major leagues (Los Alamos, NCAR, Livermore,
  aircraft/auto/oil industry)
• This will (I hope) prepare you to be adaptable to
  Fortran (and other languages) on other platforms
  using other compilers and tools

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How-to-write-programs Issues

• The operating system (in this case, Unix)
• The development environment
• editor (you are free to choose)
• we will not use a GUI (graphical user interface)
• we will use a command line interface
• we will use a makefile for convenience
• Compiler to translate source code to an
  executable
• Libraries of standard routines (math functions,
  etc.)

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CSE Dept How to Write Programs

• I dont use Blackboard I do use the CSE web
  server, and almost everything will be on the web
• look up the CSE secure web page
  https//www.cse.sc.edu
• CSCE dropbox for submitting your programs
• CSCE206 group mailing list for broadcast
• CSCE individual email accounts
• www.cse.sc.edu
• www.cse.sc.edu/buell

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Bonus Points

• Computing is a human endeavor
• You should know the human history of how we got
  to where we are
• In-class bonus points 1 point on the total
  grade
• Exam bonus points 2 points on the total grade
  per exam

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Some Thoughts on Programming

• Lesser artists borrow great artists steal.
• Stravinsky
• There is a lot of code available to look at and
  use.

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From Whom Can You Steal?

• Yourselfof course, from one program to the next
• From the textyes
• From the Internetno
• From yourselfyes
• From other reference booksno
• From yourselfyes
• From the Internetno
• There is a program that lets me compare one
  program against another for similarities.

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The End
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Chapter 0 (or 1?)

• Computer organisation and architecture
• How is the machine put together
• p17-ComputerComponents.pdf

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The Program Translation Process

• Program source code (C, Fortran, Java, )
• Source is translated by a compiler
• into object code
• and then into machine code
• which forms an executable module

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Source Code

• Has symbolic names for things and permits writing
  programs in a way that is understandable by
  people.
• PROGRAM hello_world
• IMPLICIT none
• REAL r,s
• PRINT , hello, world
• PRINT , My name is Duncan Buell
• r 64.0
• s SQRT(r)
• PRINT , r is,r,and its square root is,s
• STOP
• END PROGRAM hello_world

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Machine Code

• Machines dont understand Fortran
• Computers dont have a single instruction that
  prints a line of output, for example
• Machine code is the numerical language for the
  specific instructions of the machine
• one machine code instruction one machine
  operation
• The compiler (and other language translators)
  turn source code into machine code

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Object Code

• Object code is intermediate between source and
  executable
• We wont deal much with object code, and we wont
  even define it carefully
• Characteristic of object code
• the compiler turns your source into object
• references outside your own source (e.g., math
  libraries) may not be fully turned into machine
  code by the compilerthat happens later

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The Programming Process

• Problem analysis and specification
• Data organisation and algorithm design
• Coding (programming)
• Execution and testing
• Maintenance

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Political CorrectnessSafe programming

• Programs have bugs
• Programs have always had bugs
• We all do stupid, careless, things
• Its possible to be careless and still get a
  working program
• But its more likely that youll get working
  programs if you follow safe programming
  practices
• And Im going to beating these practices into you
  the entire semester!!!!!

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Prudent Programming Practices

• Failure is the norm. Youre going to fail. So
  fail in such a way that you can recover quickly
  and get it right the second time. (John Mashey)
• A working program that doesnt quite do what is
  desired has some value.
• A program that would do everything desired, if it
  worked, but doesnt work, has almost no value.
• Make it right before you make it better.

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The End