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notebooks/03_dataxy supprimé 100644 → 0
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0.00000000 0.00000000
0.100000001 9.98334214E-02
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6.00000000 -0.279415488
notebooks/03_gnuxy supprimé 100644 → 0
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set xlabel 'x'
set xrange [0:6]
set ylabel 'y'
set yrange [-1.2:1.2]
plot "03_dataxy" using 1:2 title 'sin(x)' with lines lt rgb "red"
pause -1
notebooks/Untitled.ipynb → notebooks/training_fortran.ipynb
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Voir le fichier @ 55947267
%% Cell type:markdown id:10d0e3c5 tags:
## Introduction to structured programming with Fortran
### Why to learn Fortran ?
* Because of the execution speed of a program
* Well suited for numerical computations : more than **45% of scientific applications** are in Fortran
### Getting started
#### Hello World
%% Cell type:code id:00ec1776 tags:
``` Fortran
program hello_world
implicit none ! important
print *, "Hello World!"
end program hello_world
```
%% Cell type:markdown id:c4b788f0 tags:
#### Data Type Declarations and Assignments
%% Cell type:code id:ffd3f0c3 tags:
``` Fortran
program data_type
implicit none
real x, y
integer i, j
logical flag
integer matrix(2,2)
character(80) month
character(len=80) months(12)
character family*16
real, dimension(12) :: small_array
character(len=80), dimension(24) :: screen
integer, parameter :: it = 100
i = 1
j = i+2
x = 85.8
y = 3.5*cos(x)
month="december"
months(:)="empty"
months(12)=month
flag = .TRUE.
family = "GEORGE P. BURDELL"
print*,family(:6)
print*,family(8:9)
print*,family(11:)
print*,family(:6)//FAMILY(10:)
end
```
%% Cell type:markdown id:133046ed tags:
#### Arithmetic Assignments
The result of any integer divide is truncated to the integer value less than the correct decimal answer for the division. The result of this is that changing the order of operations can make a big difference in the answers. Notice how parentheses force more expected results.
%% Cell type:code id:13343800 tags:
``` Fortran
program arith
implicit none
real r2,r3,r4,r5,r6,ans1,ans2,ans3
integer i2,i3,i4,i5,i6,ians1,ians2,ians3,ians4
data r2/2./,r3/3./,r4/4.0/,r5/5.0/
data i2,i3,i4,i5/2,3,4,5/
ians1=i2*i3/i5
ians2=i3/i5*i2
ians3=i2*(i3/i5)
ians4=(i3/i5)*i2
print *, '2*3/5 =', ians1, ', 3/5*2 =',ians2,', 2*(3/5) =',ians3 ,', (3/5)*2 =',ians4
end program arith
```
%% Cell type:markdown id:cabea667 tags:
Real arithmetic behaves more uniformly:
%% Cell type:code id:e1de5730 tags:
``` Fortran
program arith
implicit none
real r2,r3,r4,r5,r6,ans1,ans2,ans3
integer i2,i3,i4,i5,i6,ians1,ians2,ians3,ians4
data r2/2./,r3/3./,r4/4.0/,r5/5.0/
data i2,i3,i4,i5/2,3,4,5/
ans1=r2*r3/r5
ans2=r3/r5*r2
ans3=(r3/r5)*r2
print *, '2.0*3.0/5.0 =', ans1, ', 3.0/5.0*2.0 =',ans2,', (3.0/5.0)*2.0 =',ans3
end program arith
```
%% Cell type:markdown id:f18b85ec tags:
Watch how precedence of operations effects the following:
%% Cell type:code id:9a362858 tags:
``` Fortran
program arith
implicit none
real r2,r3,r4,r5,r6,ans1,ans2,ans3
integer i2,i3,i4,i5,i6,ians1,ians2,ians3,ians4
data r2/2./,r3/3./,r4/4.0/,r5/5.0/
data i2,i3,i4,i5/2,3,4,5/
ians1=i2+i5*i3**i2
ians2=i5*i3**i2+i2
ians3=i3**i2*i5+i2
print *, '2+5*3**2 =',ians1,', 5*3**2+2 =',ians2, ', 3**2*5+2 =',ians3
end program arith
```
%% Cell type:markdown id:5297b017 tags:
You can mix real and integers, but watch what happens
%% Cell type:code id:7d50669e tags:
``` Fortran
program arith
implicit none
real r2,r3,r4,r5,r6,ans1,ans2,ans3
integer i2,i3,i4,i5,i6,ians1,ians2,ians3,ians4
data r2/2./,r3/3./,r4/4.0/,r5/5.0/
data i2,i3,i4,i5/2,3,4,5/
ans1=r5+i3/i2
ans2=5.0+3/2
print *, '5.0+3/2 =',ans1
print *, '5.0+3/2 =',ans2
end program arith
```
%% Cell type:markdown id:222cabbc tags:
Look at what happens when I put a real in either the numerator or denominator of the division term
%% Cell type:code id:78929c6e tags:
``` Fortran
program arith
implicit none
real r2,r3,r4,r5,r6,ans1,ans2,ans3
integer i2,i3,i4,i5,i6,ians1,ians2,ians3,ians4
data r2/2./,r3/3./,r4/4.0/,r5/5.0/
data i2,i3,i4,i5/2,3,4,5/
ans1=r5+i3/r2
ans2=r5+r3/i2
print *, '5.0+3/2.0 =',ans1, ', 5.0+3.0/2 =', ans2
end program arith
```
%% Cell type:markdown id:a7d37bc2 tags:
Although Fortran normally works from left to right at a given level of precedence (does all multiply and divide from left to right before moving on to adds and subtracts). It works exponentiation from right to left when it hits 2 or more sequential exponentiation operations
%% Cell type:code id:3c2da1a9 tags:
``` Fortran
program arith
implicit none
real r2,r3,r4,r5,r6,ans1,ans2,ans3
integer i2,i3,i4,i5,i6,ians1,ians2,ians3,ians4
data r2/2./,r3/3./,r4/4.0/,r5/5.0/
data i2,i3,i4,i5/2,3,4,5/
ians1= i5**i3**i2
ians2= (i5**i3)**i2
ians3= i5**(i3**i2)
print *, '5**3**2 =',ians1, ', (5**3)**2 =',ians2, ', 5**(3**2) =',ians3
end program arith
```
%% Cell type:markdown id:8387be7a tags:
When in doubt use parentheses to get the answer that you really want.
#### Assignments exercise
%% Cell type:code id:14f6e7e2 tags:
``` Fortran
program sphere
implicit none
real pi,radius,volume,area
radius = 1.0
pi = 0.0
write(*,*) 'The value of pi is ', pi
write(*,*)
area = 0.0
volume = 0.0
write(*,*) 'For a radius ', radius
write(*,*) 'the area of a sphere is ', area
write(*,*) 'and the volume is ', volume
end
```
%% Cell type:markdown id:9a1702f7 tags:
#### Execution Control
%% Cell type:code id:41f9a8f0 tags:
``` Fortran
PROGRAM gcd
! Computes the greatest common divisor, Euclidean algorithm
IMPLICIT NONE
INTEGER :: m, n, t
WRITE(*,*) "Give positive integers m and n :"
m=5464
n=484682
WRITE(*,*) 'm:', m,' n:', n
positive_check: IF (m > 0 .AND. n > 0) THEN
main_algorithm: DO WHILE (n /= 0)
t = MOD(m,n)
m = n
n = t
END DO main_algorithm
WRITE(*,*) "Greatest common divisor: ",m
ELSE
WRITE(*,*) 'Negative value entered'
END IF positive_check
END PROGRAM gcd
```
%% Cell type:markdown id:cef2ad42 tags:
#### File-Directed Input and Output
%% Cell type:code id:8fd042c4 tags:
``` Fortran
program plot
! Program to provide plots of Sin(x)
implicit none
character label*150
real x
integer i
character xlabel*32,ylabel*32,title*32
real fx
!
! label - Character string
! xlabel - Contains a label for the x-axis
! ylabel - Contains a label for the y-axis
! title - Contains a title for the plot
!
! Drive a separate true graphics program (gnuplot)
!
! First set up the command file for gnuplot
!
xlabel="'x'"
ylabel="'y'"
title="'sin(x)'"
open (112,file='03_gnuxy')
!
label='set xlabel '//xlabel
write(112,*)label
write(112,*)'set xrange [0:6]'
label='set ylabel '//ylabel
write(112,*)label
write(112,*)'set yrange [-1.2:1.2]'
label='plot "03_dataxy" using 1:2 title '//title
label=trim(label)//' with lines lt rgb "red"'
write(112,*) label
write (112,*) 'pause -1'
close(112)
!
! Generate x-y pairs for the graph
!
open (112,file='03_dataxy')
do i=0,60
x=.1*i
fx=sin(x)
write(112,*) x,fx
enddo
close(112)
!
end program
```
%% Cell type:markdown id:558d962e tags:
%% Cell type:markdown id:31f27416 tags:
This code is going to create 2 files: "03_dataxy" and "03_gnuxy".
The idea is to use a linux plotting tool called "GNUplot" to make a graph: the first file is the data for the graph, the second one is the gnuplot script using these data.
```bash
gnuplot 03_gnuxy
```
<img src="../assets/sin.png">
<img src="https://gogs.elic.ucl.ac.be/pbarriat/learning-fortran/raw/master/assets/sin.png">
%% Cell type:code id:df362a1a tags:
``` Fortran
program newton
implicit none
! Use a Newton iteration to solve a polynomial equation
integer :: i
write(*,*) 'Try to solve "x**3+x-10=0"'
write(*,*) 'What is your initial guess for the solution?'
do while( .TRUE. )
write(*,*)
exit
end do
end program
! ******************************************************************************************
subroutine derivate()
! Evaluate the function f(x)=x**3+x-10
! also return the derivative of the function
end subroutine
```
%% Output
Try to solve "x**3+x-10=0"
What is your initial guess for the solution?
%% Cell type:code id:4b517d6b tags:
``` Fortran
PROGRAM test_arg
implicit none
integer a,b,c
common /arg/ a,b,c
a = 2
c = 1
print *, 'Before the call:'
print *, 'a = ',a,', b = ',b,', c = ',c
call sub
print *, 'After the call:'
print *, 'a = ',a,', b = ',b,', c = ',c
END PROGRAM
SUBROUTINE sub
implicit none
integer a,b,c
common /arg/ a,b,c
b = a + c
c = c + 1
END SUBROUTINE
```
%% Output
Before the call:
a = 2 , b = 0 , c = 1
After the call:
a = 2 , b = 3 , c = 2
%% Cell type:code id:71f26006 tags:
``` Fortran
MODULE arg
implicit none
integer :: a,b,c
real(8) :: x
END MODULE arg
! * * * * * * *
PROGRAM test_arg
USE arg
implicit none
a = 2
c = 1
write(*,*) 'Before the call:'
write(*,'(3(A5,I3))') ' a = ',a,', b = ',b,', c = ',c
call sub
write(*,*) 'After the call:'
write(*,'(3(A5,I3))') 'a = ',a,', b = ',b,', c = ',c
END PROGRAM test_arg
! * * * * * * *
SUBROUTINE sub
USE arg, only : a,b,c ! seuls a b et c sont utiles
implicit none
b = a + c
c = c + 1
END SUBROUTINE sub
```
%% Output
Before the call:
a = 2, b = 0, c = 1
After the call:
a = 2, b = 3, c = 2
%% Cell type:code id:e3791d4f tags:
``` Fortran
PROGRAM test_namelist
implicit none
real(8) lon_min, lon_max, lat_min, lat_max
NAMELIST/namlon/ lon_min, lon_max
NAMELIST/namlat/ lat_min, lat_max
write(*,*) 'Before:'
call print_res(lon_min, lon_max, lat_min, lat_max)
open(161,file='../src/07_namelist.def',status='old',form='formatted')
read(161,NML=namlon)
write(*,*) 'Between:'
call print_res(lon_min, lon_max, lat_min, lat_max)
read(161,NML=namlat)
close (161)
write(*,*) 'After:'
call print_res(lon_min, lon_max, lat_min, lat_max)
END
SUBROUTINE print_res(a,b,c,d)
implicit none
real(8), intent(in) :: a,b,c,d
write(*,'(4(A12,F6.2))') ' lon_min = ',a,', lon_max = ',b, &
', lat_min = ',c,', lat_max = ',d
RETURN
END
```
%% Output
Before:
lon_min = 0.00, lon_max = -0.00, lat_min = 0.00, lat_max = -0.00
Between:
lon_min = 0.00, lon_max = 360.00, lat_min = 0.00, lat_max = -0.00
After:
lon_min = 0.00, lon_max = 360.00, lat_min = -90.00, lat_max = 90.00
%% Cell type:code id:27748335 tags:
``` Fortran
```
......
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