小白求助

积分方法看另一个帖子吧。fortran我用的gfortran和ifort，windows下可以用visual fortran，我没用过。

!.....Solute one-dimension integration...............
program main
!a, b are boundary
!n is the number to divide the region
!dx = (b-a)/(n-1)
implicit real (a-h,o-z)
implicit integer (i-n)
real,external :: integrate
a=0.
b=3.14159
n=101
write(*,*) integrate(a,b,n,dx)
stop
end
!.........................................
function integrate(a,b,n,dx)
real:: a,b,dx
real,allocatable :: x(:),f(:)
integer :: i,j,n
real :: integrate
real,external :: func
dx=(b-a)/(n-1)
allocate(x(n),f(n))
x(1) = a
f(1) = func(x(1))
do i=2,n
x(i) = x(i-1)+dx
f(i) = func(x(i))
end do
integrate = sum(f)*dx - 0.5*(f(1)+f(n))*dx
return
end
!.............................................
function func(x)
real :: x
real :: func
func = sin(x)
return
end