Física Computacional Conceptos de programación.

Transcription

1 Física Computacional Conceptos de programación. F. A. Velázquez-Muñoz Departamento de Física CUCEI UdeG 6 de febrero de 2015

2 Sistemas Operativos ms-dos windows linux suse; redhat; ubuntu; etc. unix Mac OSx

3 usuario aplicación sistema operativo hardware

4 Lenguajes de Programacón: Matlab Fortran C++ Pascal Basic Java etc.

5 MatLab (MATrix LABoratory) The Language of Technical Computing High-level language for numerical computation, visualization, and application development Interactive environment for iterative exploration, design, and problem solving. Mathematical functions for linear algebra, statistics, Fourier analysis, filtering, optimization, numerical integration, and solving ordinary differential equations. Built-in graphics for visualizing data and tools for creating custom plots Development tools for improving code quality and maintainability and maximizing performance Tools for building applications with custom graphical interfaces Functions for integrating MATLAB based algorithms with external applications and languages such as C, Java,.NET, and Microsoft R Excel R

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7 Fortran (Formula Translating System). is a general-purpose, imperative programming language that is especially suited to numeric computation and scientific computing

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9 Declaración y uso de Variables

10 Tipos de Variables INTEGER: entero REAL: real COMPLEX: complejo LOGICAL: logica (verdadero o falso) CHARACTER: caracter

11 En un programa de fortran, la forma de escribir la declaración de variables es: program v a r s i n t e g e r : : i r e a l : : a complex : : img l o g i c a l : : i o c h a r a c t e r (10) : : fecha i =1 a =2.33 img=cmplx ( 1, 2 ) i o = t r u e fecha = 2015/01/01 w r i t e ( 6, ) w r i t e ( 6, ) w r i t e ( 6, ) w r i t e ( 6, ) w r i t e ( 6, ) i a img i o f e c h a end program v a r s

12 El resultado que muestra el programa en pantalla es: compu$./a.out ( , ) F 2015/01/01

13 c l e a r a l l i =1 a =2.33 img=1+2 i i o=f a l s e f e c h a = 2015/01/01

14 i = a = 1 img = 3 i o = f e c h a = 2015/01/01

15 program prog r e a l : : a, b, c a =1.2 b=3.4 c=a+b w r i t e ( 6, ) c end program prog

16 program prog r e a l : : a, b, c r e a d (, ) r e a d (, ) a b c=a+b w r i t e ( 6, ) c end program prog

17 program prog r e a l : : a, b, c open ( u n i t =100, f i l e = d a t o s. dat ) r e a d (100, ) a r e a d (100, ) b c l o s e ( ) c=a+b w r i t e ( 6, ) c end program prog

18 program prog r e a l : : a, b, c open ( u n i t =100, f i l e = d a t o s. dat ) r e a d ( 1 0 0, ) a r e a d ( 1 0 0, ) b c l o s e ( ) 110 format ( F7. 2 ) c=a+b w r i t e ( 6, ) a w r i t e ( 6, ) b w r i t e ( 6, ) c open ( u n i t =200, f i l e = d a t o s. out ) w r i t e (200, ) c c l o s e ( ) end program prog

19 Formato para datos de entrada y salida en fortran sintaxis: write/read (UNIT,FORMAT) variables (UNIT LABEL,FORMAT LABEL) variables label format (format-code) ejemplo: write(*,900) i,x 900 format(i4,f8.3) write/read

20 A: text string D: double precision numbers, exponent notation E: real numbers, exponent notation F: real numbers, fixed point format I: integer X: horizontal skip (space) /: vertical skip (new line) n FC w.d

21 Los indices se usan para identificar a un elemento de un arreglo de variables. por ejemplo: Se se define a(1)=10; a(2)=20; a(3)=30 el arreglo es de dimensión 1 x 3. Si queremos multiplicar el arreglo de numeros a por 2, tenemos que hacer: b(1)=2*a(1) b(2)=2*a(2) b(3)=2*a(3) para n datos, la forma general es: b(j) = 2 a(j) para j = 1, 2, 3,..., n.

22 Cuando se requiere hacer una tarea de forma repetitiva utilizamos un ciclo. para j=1 hasta n TAREA termina En fortran do j=1,n b(j)=2*a(j) enddo En MatLab foro j=1:n b(j)=2*a(j); end

23 program prog i n t e g e r : : i r e a l : : a, b, c c h a r a c t e r ( 3 0 ) : : head c h a r a c t e r ( 3 0 ) : : b a s u r a open ( u n i t =100, f i l e = e s t a c i o n. dat ) r e a d ( 1 0 0, ) head r e a d ( 1 0 0, (A) ) b a s u r a r e a d ( 1 0 0, ) i, a, b c l o s e ( ) 101 format (A) 102 format ( I1, F5. 1, F6. 2 ) c=a+b w r i t e ( 6, ) w r i t e ( 6, ) head i, a, b, c open ( u n i t =200, f i l e = e s t a c i o n. out ) w r i t e (200, ) d a t o s de s a l i d a w r i t e ( 2 0 0, ( I1, 3 F6. 2 ) ) i, a, b, c c l o s e ( ) end program prog

24 program prog i n t e g e r : : i r e a l : : a, b, c c h a r a c t e r ( 3 0 ) : : head c h a r a c t e r ( 3 0 ) : : b a s u r a d i m e n s i o n i ( 5 ), a ( 5 ), b ( 5 ), c ( j ) open ( u n i t =100, f i l e = e s t a c i o n 1. dat ) r e a d ( 1 0 0, ) head r e a d ( 1 0 0, (A) ) b a s u r a do j =1,5 r e a d ( 1 0 0, ) i ( j ), a ( j ), b ( j ) enddo c l o s e ( ) 101 format (A) 102 format ( I1, F5. 1, F6. 2 ) do j =1,5 c ( j )=a ( j )+b ( j ) enddo w r i t e ( 6, ) head do j =1,5 w r i t e ( 6, ( I1, 3 F6. 2 ) ) i ( j ), a ( j ), b ( j ), c ( j ) enddo open ( u n i t =200, f i l e = e s t a c i o n 1. out ) write (200,201) datos de s a li da do j =1,5 w r i t e ( 2 0 0, ) i ( j ), a ( j ), b ( j ), c ( j ) enddo c l o s e ( ) 201 format (A) 202 format ( I3, 3 F8. 4 ) end program prog

25 Ejemplo. Programa para evaluar y graficar una función

26 program f u n c i o n i n t e g e r : : i, n r e a l, a, b r e a l, d i m e n s i o n ( 1 0 ) : : x, f a =0. e0 b=2. e0 n=10 dx=(b a )/ n x (1)= a f (1)=x 2. e0 do i =1,n x ( i )=a+i dx f ( i )=x 2 w r i t e ( 6, ) x, f enddo end program f u n c i o n

27 program f u n c i o n p a r a m e t e r ( n=10) i n t e g e r : : i r e a l, a, b r e a l, d i m e n s i o n ( n ) : : x, f a =0. e0 b=2. e0 dx=(b a )/ n x (1)= a f (1)= x ( 1 ) 2. e0 do i =1,n x ( i )=a+i dx f ( i )=x ( i ) 2 enddo open ( u n i t =100, f i l e = f u n c d a t a. dat ) do i =1,n w r i t e ( 1 0 0, ) x ( i ), f ( i ) enddo c l o s e ( ) 200 format (2 f ) end program f u n c i o n

28 program f u n c i o n c l e a r a l l p a r a m e t e r ( n=10) i n t e g e r : : i r e a l, a, b r e a l, d i m e n s i o n ( n ) : : x, f a =0. e0 b=2. e0 dx=(b a )/ n load funcdata. dat x=f u n c d a t a ( :, 1 ) ; f=f u n c d a t a ( :, 2 ) ; c l f p l o t ( x, f, o ) x (1)= a f (1)= x ( 1 ) 2. e0 do i =1,n x ( i )=a+i dx f ( i )=x ( i ) 2 enddo open ( u n i t =100, f i l e = f u n c d a t a. dat ) do i =1,n w r i t e ( 1 0 0, ) x ( i ), f ( i ) enddo c l o s e ( ) 200 format (2 f ) end program f u n c i o n

29 program f u n c i o n c l e a r a l l p a r a m e t e r ( n=10) i n t e g e r : : i r e a l, a, b r e a l, d i m e n s i o n ( n ) : : x, f a =0. e0 b=2. e0 dx=(b a )/ n x (1)= a f (1)= x ( 1 ) 2. e0 do i =1,n x ( i )=a+i dx f ( i )=x ( i ) 2 enddo open ( u n i t =100, f i l e = f u n c d a t a. dat ) do i =1,n w r i t e ( 1 0 0, ) x ( i ), f ( i ) enddo c l o s e ( ) 200 format (2 f ) end program f u n c i o n load funcdata. dat x=f u n c d a t a ( :, 1 ) ; f=f u n c d a t a ( :, 2 ) ; c l f p l o t ( x, f, o )

30 sub rutinas

31 programas: principal.f ; subrutina rutina.f compilacion: pgf90 principal.f rutina.f -o principal.out program p r i n c i p a l s u b r o u t i n e r u t i n a ( x, y, z ) r e a l : : a, b a=3 b=4 c a l l r u t i n a ( a, b ) end program p r i n c i p a l r e a l : : x, y, z z=s q r t ( x 2+y 2) w r i t e ( 6, ) r e t u r n end z

32 compu$ pgf90 principal.f rutina.f -o prin.out principal.f: rutina.f: compu$./prin.out

33 programas: principal.f ; subrutina rutina.f compilacion: pgf90 principal.f rutina.f -o principal.out program p r i n c i p a l s u b r o u t i n e r u t i n a ( x, y, z ) r e a l : : a, b, c a=3 b=4 c a l l r u t i n a ( a, b, c ) c a l l wrt ( c ) end program p r i n c i p a l c s u b r o u t i n e wrt ( v a r ) r e a l : : x, y, z z=s q r t ( x 2+y 2) w r i t e ( 6, ) r e t u r n end z w r i t e ( 6, ) w r i t e ( 6, ) v a r c end

34 program p r i n c i p a l program p r i n c i p a l p a r a m e t e r ( n=10) r e a l : : a, b, x, f a =0. e0 b=10. e0 dt =(b a )/ n open ( u n i t =100, f i l e = f u n c d a t a 3. dat ) do i =1,n t=t+dt c a l l e v a l ( t, f ) p a r a m e t e r ( n=10) r e a l dt, a, b r e a l, d i m e n s i o n ( n ) : : t, f a =0. e0 b=10. e0 dt =(b a )/ n do i =1,n t ( i )=( i 1) dt c a l l e v a l ( t ( i ), f ( i ) ) w r i t e (1 0 0,2 00) enddo 200 format (2 F11. 4 ) t, f enddo open ( u n i t =100, f i l e = f u n c d a t a 4. dat ) do i =1,n w r i t e ( 1 0 0, ) t ( i ), f ( i ) enddo c l o s e ( ) 200 format (2 F11. 4 ) end program p r i n c i p a l C s u b r o u t i n e e v a l ( t, f ) r e a l : : x, f r e t u r n end C f = 9.81 t 2 end program p r i n c i p a l C s u b r o u t i n e e v a l ( t, f ) r e a l : : x, f r e t u r n end C f = 9.81 t 2

35 archivo de salida funcdata3.dat c l e a r a l l dat=l o a d ( f u n c d a t a 4. dat ) ; t=dat ( :, 1 ) ; f=dat ( :, 2 ) ; c l f p l o t ( t, f,. k, MarkerSize, 2 0, L i n e w i d t h, 2 ) t i t l e ( c a i d a l i b r e, FontSize, 1 8 ) x l a b e l ( tiempo [ s eg ], FontSize, 1 8 ) y l a b e l ( d i s t a n c i a [m], FontSize, 1 8 ) s e t ( gca, FontSize, 1 8 ) g r i d on p r i n t depsc p r i n c i p a l 4

36 0 caida libre distancia [m] tiempo [seg]