BIL106 E Introduction to Scientific & Engineering Computing

1. BIL106E Introduction to Scientific & Engineering Computing Hüseyin TOROS, Ph.D. istanbul Technical University Faculty of Aeronautics and Astronautics Dept. of Meteorological Engineering Voice: 285 31 27 E-mail: toros@itu.edu.tr http://atlas.cc.itu.edu.tr/~toros An important fraction of our interaction will be via e-mail Useful Pages: http://www.be.itu.edu.tr/ http://atlas.cc.itu.edu.tr/~toros/bil106e.htm http://atlas.cc.itu.edu.tr/~F90/mainindex.html http://www.fortran.com/ http://www.foldoc.org (Free OnLine Dictionary of Computing) F Compiler: Read this first, Full installer (3.4Mb): win95nt.exe For more information syllabus_F 07/26/09 Introduction toScientific & Engineering Computing

2. History & Background • Fortran was originally created by a team lead by John Backus at IBM in 1957. Originally, the name was in all capital letters, but current usage is only requiring that the first letter be capitalized. • The name Fortran stands for FORmula TRANslator. It was originally aimed at scientific calculation and had limited support for working with characters. • Until the C language became popular, it was one of the few high level languages with a high level of portability between different computer systems. • Several websites indicate that the work on Fortran was started in 1954 and released commercially in 1957. • 20 September 1954 may have been the day that a small Fortran program was first successfully compiled. 2 07/26/09 Introduction toScientific & Engineering Computing

3. History & Background • There have been several versions of Fortran. Fortran I, II and III are considered obsolete. • The oldest Fortran versions which are considered of much use today were Fortran IV, and Fortran 66, which, as the name implies, was released in 1966. • All later versions of Fortran are numbered after the year the standard was released. • The versions of Fortran most commonly remaining in use are Fortran 77, Fortran 90, and Fortran 95. • It was the first High Levelor Third Generation programming language. • Before it, all Programs werewritten in Assembler, where one Program Instruction corresponded to asingle machine operation, and each model of computer featured its own Instruction Set.

4. Why Fortran? • Among many computer scientists Fortran is the most widely used language in scientific computing, especially when high performance is required. • Concise language • Good compilers producing efficient machine code • Legacy: high-quality mathematical libraries available • New version have features helpful for parallelization 4 07/26/09 Introduction toScientific & Engineering Computing

5. The Flanguage F is a subset of FORTRAN. The F compiler was written by Walt Brainerd Fortran 90 F Fortran 77 • Easy to • learn • implement • understand • Powerful enough for use in large programs • Download F_World compiler, Installed F_World 5 07/26/09 Introduction toScientific & Engineering Computing

7. GNU Fortran and GCC GNU Fortran is a part of GCC, the GNU Compiler Collection. GCC consists of a collectionof front ends for various languages, which translate the source code into a languageindependentform called GENERiC. This is then processed by a common middle end which provides optimization, and then passed to one of a collection of back ends which generatecode for different computer architectures and operating systems. Functionally, this is implemented with a driver program (gcc) which provides thecommand-line interface for the compiler. it calls the relevant compiler front-end program(e.g., f951 for Fortran) for each file in the source code, and then calls the assembler andlinker as appropriate to produce the compiled output. in a copy of GCC which has beencompiled with Fortran language support enabled, gcc will recognize files with ‘.f’, ‘.for’,‘.ftn’, ‘.f90’, ‘.f95’, ‘.f03’ and ‘.f08’ extensions as Fortran source code, and compile itaccordingly. 7 07/26/09 Introduction toScientific & Engineering Computing

8. GNU Fortran and GCC A gfortran driver program is also provided, which is identical to gcc exceptthat it automatically links the Fortran runtime libraries into the compiled program. Source files with ‘.f’, ‘.for’, ‘.fpp’, ‘.ftn’, ‘.F’, ‘.FOR’, ‘.FPP’, and ‘.FTN’ extensions are treated as fixed form. Source files with ‘.f90’, ‘.f95’, ‘.f03’, ‘.f08’, ‘.F90’, ‘.F95’,‘.F03’ and ‘.F08’ extensions are treated as free form. The capitalized versions of eitherform are run through preprocessing. Source files with the lower case ‘.fpp’ extension are also run through preprocessing. More information about gfortran 8 07/26/09 Introduction toScientific & Engineering Computing

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10. Basic statements • A program is just a sequence of lines of text. • Execution of the program is a separate process that goes on inside the computer when the program is executed. • The program statements are static, or fixed, while the execution process is dynamic, or changing. • The statements exists in space, and the execution occurs in a time dimension. First instruction Execution of first instruction Execution of last instruction Last instruction Correspondence between the program and its execution process 10 07/26/09 Introduction toScientific & Engineering Computing

11. General Fortran Program Structure : Fortran constitutes an Imperative High Level programming language, in that the Source Code in Programs is not directly understood, let alone executed by the hardware. Instead, the Code is submitted to a Compiler which writes out a Binary or Executable Module, containing (Machine Code) Instructions appropriate (and often peculiar to) the Hardware being used. All Fortran Programs begin with a "Non Executable" Part, where Variables, Arrays, and Constants may be declared and initialized. The "Executable" Part follows, in which all computations, logic, and File handling take place. 07/26/09 Introduction toScientific & Engineering Computing

12. Diagrammatic form of a Fortran Program : PROGRAM Statement : Optional to Name Program Non Executable Part : Non Executable Statements Executable Part : Executable Statements END : Completes Executable Part

13. !Our First Program program hello implicit none !This is my first program write (*,*) “Hello World!” end program hello ! The bold keywords tell the compiler wherethe program begins andends.

14. ! A First Program -- Comments • program hello • implicit none • !This is my first program • write (*,*) “Hello World!“ • end program hello • !Comments are preceded by a “!” • !All characters following the exclamation markon that line are ignored by the compiler • !The “!” inside the Hello World! string is not part of a comment 07/26/09 Introduction toScientific & Engineering Computing

15. How Do I Run The Program? • First, prepare the program using aneditor to enter the program text. • A plain text editor such as Notepad, vi, nano, • Save the program text with the suffix .f90 (e.g. Hello.f90) • Run the FORTRAN compiler taking its inputfrom this file and producing an executable program • If you used a plain text editor, run the following from the command window. • gfortran –fimplicit-none –W hello.f90 -o hello.exe • Run the executable program (in the .exe file) • gfortran hello.f90  ./a.out • From F_world menu run program commands 07/26/09 Introduction toScientific & Engineering Computing

16. Comments • Comments are used to signal the intent of the programmer • Improve readability and understanding • An important aid to debugging and maintaining code • Comments can appear anywhere in the program • When the compiler encounters a “!” (that is not contained inside a string) it ignores the rest of the line • Comments are only there for someone reading the program, not for the compiler to use. • Make Useful Comments

17. Useful Comments • Not Useful: ! Add 1 to a a = a + 1 • More Useful: ! Increment to account for new user login a = a + 1 • Sometimes, Not Necessary: NumUsersLoggedIn = NumUsersLoggedIn + 1

18. !READ iN THREE iNTEGERS FROM THE KEYBOARD AND !PRINT THEM TO !THE SCREEN IN A DIFFERENT ORDER program number integer:: num1, num2, num3 print *, 'Enter 3 integers: ' read *, num1, num2, num3 print *, num2, num3, num1 stop end program number

19. ! Write a program that reads in a temperature in Celsius and converts it ! to Fahrenheit, then prints result to the screen ! Read in the celsius temperature and print out the fahrenheit temp program centigrade_to_fahrenheit implicit none ! Variable declarations; real :: temp_c, temp_f ! Ask for Centigrate temperature; print *, "What is the Centigrade temperature? " read *, temp_c ! Convert to Fahrenheit; temp_f = 9.0 * temp_c / 5.0 + 32.0 ! Print both temperatures; print *, temp_c, "C=", temp_f,"F" end program centigrade_to_fahrenheit

20. En iyi Buğday Her yil yapilan "en iyi buğday" yarişmasini yine ayni çiftçi kazanmişti. Çiftçiye bu işin sirri soruldu. Çiftçi: -Benim sirrimin cevabi, kendi buğday tohumlarimi komşularimla paylaşmakta yatiyor, dedi. -Elinizdeki kaliteli tohumlari rakiplerinizle mi paylaşiyorsunuz? Ama neden böyle bir şeye ihtiyaç duyuyorsunuz? diye sorulduğunda, -Neden olmasin, dedi çiftçi. -Bilmediğiniz bir şey var; rüzgâr olgunlaşmakta olan buğdaydan poleni alir ve tarladan tarlaya taşir. Bu nedenle, komşularimin kötü buğday yetiştirmesi demek, benim ürünümün kalitesinin de düşük olmasi demektir. Eğer en iyi buğdayi yetiştirmek istiyorsam, komşularimin da iyi buğdaylar yetiştirmesine yardimci olmam gerekiyor. Kalkınmada süreklilik çevremizle beraber olduğunda mümkündür. Sevgi ve paylaşmak en yakininizdan başlar. Sonra yayilarak devam eder. Kin, cimrilik, nefret kimsenin hoşlanacaği davranişlar değildir. 07/26/09 Introduction toScientific & Engineering Computing

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22. ! Write a program to calculates average of two number program average real::x,y,ave ! Type declarations read*,x,y ! Read the values Ave=(x+y)/2.0 !Calculation print*,”x=“,x, ”y=“,y print*,”average is=“,ave endprogram average 22 07/26/09 Introduction toScientific & Engineering Computing

23. Basic statements Type declarations The principal data types for F numerical data are: real, integer, complex, logical, character. 23 07/26/09 Introduction toScientific & Engineering Computing

24. Operators and assignment • The following operators are supported. Notice that the relational operators of the form .op. (like .EQ.) have not been included. The Fortran 90/95 feature that permits new operator definition is included and allows the .op. form. There is also a defined assignment capability. Arithmetic operators +, -, * ,/,** (Addition, Subtraction, Multiplication,Division,Exponentiation) • Relational operators <, <=, ==, /=, >, >= • Logical operators .not., .and., .or., .eqv., .neqv. Character concatenation // • Defined operator .letters. 24 07/26/09 Introduction toScientific & Engineering Computing

25.         program message! variable declaration part        character (len=25):: name , surname         character(len=200):: my_message!initial values!read name      print *, “ Please input your name, then press enter”        read *, name!read surname      print *, " Please input your surname, then press enter"        read *, surname!        read * name  surname!read message      print *, " Please input your message, then press enter"        read *, my_message!printing part       print*        print*, " Hello !"      print*        print  *, " My name is :", name ," ", surname        print*        print  *,my_message      pause        end program message 25 07/26/09 Introduction toScientific & Engineering Computing

26. ! Write a program to calculate sum, multiplication and division of three numbers        program numbers        real::real_1, real_2, real_3, sum1, multi, div1!initial values    !reading numbers      print *, " Please input three numbers"        read *, real_1, real_2, real_3!summation      sum1= real_1  + real_2 + real_3      print*, sum1! multiplication part      multi= real_1 * real_2 * real_3        print *, multi! division part      div1= real_1 / real_2 / real_3        print *, multi!print new values        print*        end program numbers 26 07/26/09 Introduction toScientific & Engineering Computing

27. ! This program adds two numbers and displays the result program add real:: a,b,c print*,"Input two numbers (include a decimal point)" read*,a,b c=a+b print*,"The sum of the numbers you entered is", c end program add program sumofnumbers 27 07/26/09 Introduction toScientific & Engineering Computing

28. ! Write a program to calculates area of a rectangle program area_of_rectangle real::x,y,area ! x and y are the edges of rectangle read*,x,y area=x*y print*,”x=“,x, ”y=“,y print*,”area of rectangle=“,area endprogram area_of_rectangle 28 07/26/09 Introduction toScientific & Engineering Computing

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30. program Radioactive_Decay !This program calculates the amount of a radioactive substance that ! remains after a specified time, given an initial amount and its half-life. ! Variables used are: ! InitalAmount : initial amount of substance (mg)‏ ! HalfLife : half-life of substance (days)‏ ! Time : time at which the amount remaining is calculated (days)‏ ! AmountRemaining : amount of substance remaining (mg)‏ !Input: InitialAmount, HalfLife, Time !Output: AmountRemaining implicit none real :: InitialAmount, HalfLife, Time, AmountRemaining ! Get values for InitialAmount, HalfLife, and Time. print *, "Enter initial amount (mg) of substance, its half-life (days)" print *, "and time (days) at which to find amount remaining:" read *, InitialAmount, HalfLife, Time ! Compute the amount remaining at the specified time. AmountRemaining = InitialAmount * 0.5 ** (Time / HalfLife)‏ ! Display AmountRemaining. print *, "Amount remaining =", AmountRemaining, "mg" end program Radioactive_Decay 30 07/26/09 Introduction toScientific & Engineering Computing

31. program kalp print*," -- --" print*," -- - - --" print*,"-- - - --" print*,"- - -" print*,"- -" print*," - '' ----" print*," - '' -" print*," - -" print*," - -" print*," - -" print*," - -" print*," -" endprogram kalp Program fortran print*," ****** oooo ++++ ttttttttt rrrr AA N N" print*," * o o + + t r r A A NN N" print*," * o o + + t r r A A N N N" print*," ****** o o + + t r r A A N N N" print*," * o o +++++ t rrrrr AAAAAAAA N N N" print*," * o o + + t r r A A N N N" print*," * o o + + t r r A A N NN" print*," * oooo + + t r r A A N N“ endprogram fortran 31 07/26/09 Introduction toScientific & Engineering Computing