70 lines
1.9 KiB
Fortran
70 lines
1.9 KiB
Fortran
!
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! project "gravity field"
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!
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!-----------------------------------------------------------------------
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module realfield
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implicit none
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!-----------------------------------------------------------------------
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! definition of structures
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!
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type massbody
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real :: posx, posy
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real :: mass = 1.0
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integer :: serial = 666
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end type
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!-----------------------------------------------------------------------
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contains
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!-----------------------------------------------------------------------
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function compute_gravity(fx, fy, body)
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real, intent(in) :: fx, fy
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type(massbody), intent(in) :: body
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real :: compute_gravity
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real :: rx, ry, dist
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rx = fx - body%posx
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ry = fy - body%posy
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dist = sqrt( (rx*rx) + (ry*ry) )
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if (dist .LT. 0.11) then
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! write (0, *) "dist too small ", dist
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compute_gravity = 0e0
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else
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compute_gravity = body%mass / (dist ** 2)
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endif
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end function
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!-----------------------------------------------------------------------
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!-
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! Compute the gravity field in a pre-allocated array relative
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! to the massbody 'moon'. Nobody know where the magic number
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! come from, sorry.
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!-
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subroutine compute_a_field(field, moon)
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real, dimension(:,:), intent(out) :: field
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type(massbody), intent(in) :: moon
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integer :: ix, iy
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real :: fx, fy
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real :: grav
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! print *, "pic size ", ubound(field, 1), "W", ubound(field, 2), "H"
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! print *, "mass body ", moon
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do ix=1, ubound(field, 1)
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fx = real(ix)
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do iy=1, ubound(field, 2)
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fy = real(iy)
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grav = compute_gravity(fx, fy, moon)
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field(ix,iy) = grav
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enddo
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enddo
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end subroutine
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!-----------------------------------------------------------------------
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!-----------------------------------------------------------------------
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end module
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