210 lines
6.2 KiB
Fortran
210 lines
6.2 KiB
Fortran
!-----------------------------------------------------------------------
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!-
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! some functions for the project "gravity field"
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!-
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!-----------------------------------------------------------------------
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module realfield
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use spitpgm ! XXX
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implicit none
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!-----------------------------------------------------------------------
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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 = 0, posy = 0
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real :: heading = 0.29
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real :: speed = 1.017
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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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subroutine compute_barycentre_bodies(astres, bcx, bcy)
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type(massbody), intent(in) :: astres(:)
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real, intent(out) :: bcx, bcy
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integer :: foo
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real :: cx, cy
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! May be we have to use DOUBLE RPECSION here ?
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cx = 0.0
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cy = 0.0
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do foo=1, ubound(astres, 1)
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cx = cx + astres(foo)%posx
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cy = cy + astres(foo)%posy
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enddo
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bcx = cx / real(ubound(astres, 1))
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bcy = cy / real(ubound(astres, 1))
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end subroutine
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!-----------------------------------------------------------------------
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subroutine print_barycentre_bodies(astres)
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type(massbody), intent(in) :: astres(:)
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real :: cx, cy
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call compute_barycentre_bodies(astres, cx, cy)
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print *, "barycentre : ", cx, cy
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end subroutine
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!-----------------------------------------------------------------------
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!-
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! make a few solid body to play with...
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!-
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! planets : an array of type(massbody) to be filled
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! coef : for setting the mass of the body
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! sx, sy : borders of the universe
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!-
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subroutine create_some_planets(planets, coef, sx, sy)
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type(massbody), intent(inout) :: planets(:)
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real, intent(in) :: coef
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integer, intent(in) :: sx, sy
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integer :: foo
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character(100) :: fmt
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fmt = "(I4, ' | ', 2(F10.2, ' '), ' | ', 2F9.3, ' ', e12.3, I7)"
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do foo=1, ubound(planets, 1)
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if (foo .EQ. 1) then
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!-
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! the first planet is the home of Johnny Root
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!-
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planets(1)%posx = sx / 2
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planets(1)%posy = sy / 2
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planets(1)%mass = 29e8
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planets(1)%serial = 1337
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planets(1)%speed = 6.666
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else
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!-
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! others are planets for peones
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!-
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planets(foo)%posx = rand() * real(sx-1)
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planets(foo)%posy = rand() * real(sy-1)
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planets(foo)%mass = 7e6 + coef*foo
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planets(foo)%heading = 3.14159 * rand()
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if (rand() .LT. 0.08) planets(foo)%speed = 3.14159
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planets(foo)%serial = foo*2 + 120
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endif
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write (*, fmt) foo, planets(foo)
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enddo
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end subroutine
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!-----------------------------------------------------------------------
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!-
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! the basis of the kluge
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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. 0.08) 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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! compute a field with only one body; and write a pic file
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!-
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subroutine build_and_write_a_field(szx, szy, moons, fname)
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integer, intent(in) :: szx, szy
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type(massbody), intent(in) :: moons(:)
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character(len=*), intent(in) :: fname
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real :: maxi, mini
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integer :: errcode, foo
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real, dimension(:,:), allocatable :: field, tmpf
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integer, dimension(:,:), allocatable :: greymap
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allocate(field(szx, szy), stat=errcode)
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allocate(tmpf(szx, szy), stat=errcode)
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field = 0.0
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do foo=1, ubound(moons, 1)
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call compute_a_field(tmpf, moons(foo))
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tmpf = tmpf * 0.019
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field = field + tmpf
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enddo
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maxi = maxval(field)
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mini = minval(field)
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! print *, "field: ", mini, maxi, maxi-mini
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allocate(greymap(szx, szy), stat=errcode)
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greymap = 65533
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! convert from real value to 16 bits int values
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where (field < 65530.0)
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greymap = int(field)
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end where
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call spit_as_pgm_16(greymap, trim(fname))
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! make valgrind happy
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deallocate(field)
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deallocate(greymap)
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end subroutine
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!-----------------------------------------------------------------------
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!-
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! Yes, I know, this is a disturbing kluge, but I like it :}
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! May be, it's time to read the doc of modern Fortran
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!-
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subroutine init_random()
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integer, dimension(3) :: tarray
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integer :: t3
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real :: dummy
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call itime(tarray)
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t3 = 8971*tarray(1) + 443*tarray(2) + tarray(3)
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write(0, '(A,3I3,A,I6)') "sranding: ", tarray, " --> ", t3
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call srand(t3)
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! after initializing the random generator engine,
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! you MUST use it for initializing the initializer
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do t3=1, 4
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dummy = rand()
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write(0, *) 'dummy ', t3, dummy
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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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