Difference between revisions of "Fortran"
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Revision as of 09:04, 7 June 2010
Fortran95 is the language of choice to program in MOHID. Although a primitive form of language it proves to be the most efficient and performant in the area of scientific computing. Still widely used in numerical computation. Here's a crash course. Here's a free manual.
Contents
Examples
Hello World program
program helloworld implicit none write (*,*) "Hello world!" end program helloworld
Hello world in a module
module modulehelloworld
contains
subroutine showhelloworld()
write(*,*) "Hello world!"
end subroutine showhelloworld
end module modulehelloworld
program helloworld use modulehelloworld, only: showhelloworld implicit none call showhelloworld end program helloworld
Subroutine
program subfunc
implicit none
real :: a,b,c,root1,root2
logical :: realroots
write (*,*) "Hello world!"
write (*,10)
read (*,*) a,b,c
call solvit(a,b,c,root1,root2,realroots)
write (*,20) root1,root2
if (realroots) then
write(*,*) 'Sorry, there are no real roots'
end if
10 format('Enter 3 coefficients')
20 format('The roots are ', 2f12.6)
end program subfunc
subroutine solvit(a,b,c,root1,root2,realroots)
!Arguments
real ::a,b,c,root1,root2
logical :: realroots
!Locals
real :: test
test = b**2-4*a*c
if(test>=0.0) then
root1 = (-b + sqrt(test))/(2.0*a)
root2 = (-b - sqrt(test))/(2.0*a)
realroots = .true.
else
realroots = .false.
end if
return
end subroutine solvit
Function
program subfunc
implicit none
real :: a,b,c,root1,root2,bigroot
logical :: realroots
write (*,*) "Hello world!"
write (*,10)
read (*,*) a,b,c
!call solvit(a,b,c,root1,root2,realroots)
!write (*,20) root1,root2
write(*,20) bigroot(a,b,c)
if (realroots) then
write(*,*) 'Sorry, there are no real roots'
end if
10 format('Enter 3 coefficients')
!20 format('The roots are ', 2f12.6)
20 format('The biggest root is ', f12.6)
end program subfunc
function bigroot(a,b,c)
!Arguments
real :: a,b,c,bigroot
!Local
real :: root1, root2, test
if(test>=0.0) then
root1 = (-b + sqrt(test))/(2.0*a)
root2 = (-b - sqrt(test))/(2.0*a)
if (root1 .gt. root2) then
bigroot = root1
else
bigroot = root2
end if
else
bigroot = -9.0e35
end if
return
end function bigroot
Variables
Types
Interface procedure
Arrays
If
Do
Loop that increments the counter.
do i=1,10 write(*,*) 'Couting ',i end do
Loop that increments the counter by two.
do i=1,21,2 write(*,*) 'Counting pair ',i-1 end do
Loop that decrements the counter.
do i=20,1,-1 write(*,*) 'Reverse counting of even ',i*2-1 end do
===Case===
==Sample==
program average
! Read in some numbers and take the average
! As written, if there are no data points, an average of zero is returned
! While this may not be desired behavior, it keeps this example simple
implicit none
real, dimension(:), allocatable :: points
integer :: number_of_points
real :: average_points=0., positive_average=0., negative_average=0.
write (*,*) "Input number of points to average:"
read (*,*) number_of_points
allocate (points(number_of_points))
write (*,*) "Enter the points to average:"
read (*,*) points
! Take the average by summing points and dividing by number_of_points
if (number_of_points > 0) average_points = sum(points) / number_of_points
! Now form average over positive and negative points only
if (count(points > 0.) > 0) then
positive_average = sum(points, points > 0.) / count(points > 0.)
end if
if (count(points < 0.) > 0) then
negative_average = sum(points, points < 0.) / count(points < 0.)
end if
deallocate (points)
! Print result to terminal
write (*,'(a,g12.4)') 'Average = ', average_points
write (*,'(a,g12.4)') 'Average of positive points = ', positive_average
write (*,'(a,g12.4)') 'Average of negative points = ', negative_average
end program average
