1 ! Copyright (C) 2008, 2009 Slava Pestov.
2 ! See http://factorcode.org/license.txt for BSD license.
3 USING: accessors specialized-arrays fry kernel locals math
4 math.constants math.functions math.vectors prettyprint
5 combinators.smart sequences hints arrays ;
6 SPECIALIZED-ARRAY: double
9 : solar-mass ( -- x ) 4 pi sq * ; inline
10 CONSTANT: days-per-year 365.24
13 { location double-array }
14 { velocity double-array }
15 { mass float read-only } ;
17 : <body> ( location velocity mass -- body )
18 [ days-per-year v*n ] [ solar-mass * ] bi* body boa ; inline
20 : <jupiter> ( -- body )
21 double-array{ 4.84143144246472090e+00 -1.16032004402742839e+00 -1.03622044471123109e-01 }
22 double-array{ 1.66007664274403694e-03 7.69901118419740425e-03 -6.90460016972063023e-05 }
23 9.54791938424326609e-04
26 : <saturn> ( -- body )
27 double-array{ 8.34336671824457987e+00 4.12479856412430479e+00 -4.03523417114321381e-01 }
28 double-array{ -2.76742510726862411e-03 4.99852801234917238e-03 2.30417297573763929e-05 }
29 2.85885980666130812e-04
32 : <uranus> ( -- body )
33 double-array{ 1.28943695621391310e+01 -1.51111514016986312e+01 -2.23307578892655734e-01 }
34 double-array{ 2.96460137564761618e-03 2.37847173959480950e-03 -2.96589568540237556e-05 }
35 4.36624404335156298e-05
38 : <neptune> ( -- body )
39 double-array{ 1.53796971148509165e+01 -2.59193146099879641e+01 1.79258772950371181e-01 }
40 double-array{ 2.68067772490389322e-03 1.62824170038242295e-03 -9.51592254519715870e-05 }
41 5.15138902046611451e-05
45 double-array{ 0 0 0 } double-array{ 0 0 0 } 1 <body> ;
47 : offset-momentum ( body offset -- body )
48 vneg solar-mass v/n >>velocity ; inline
50 TUPLE: nbody-system { bodies array read-only } ;
52 : init-bodies ( bodies -- )
53 [ first ] [ double-array{ 0 0 0 } [ [ velocity>> ] [ mass>> ] bi v*n v+ ] reduce ] bi
54 offset-momentum drop ; inline
56 : <nbody-system> ( -- system )
57 [ <sun> <jupiter> <saturn> <uranus> <neptune> ] output>array nbody-system boa
58 dup bodies>> init-bodies ; inline
60 :: each-pair ( bodies pair-quot: ( other-body body -- ) each-quot: ( body -- ) -- )
63 bodies i 1 + tail-slice [
68 : update-position ( body dt -- )
69 [ dup velocity>> ] dip '[ _ _ v*n v+ ] change-location drop ;
71 : mag ( dt body other-body -- mag d )
72 [ location>> ] bi@ v- [ norm-sq dup sqrt * / ] keep ; inline
74 :: update-velocity ( other-body body dt -- )
75 dt body other-body mag
76 [ [ body ] 2dip '[ other-body mass>> _ * _ n*v v- ] change-velocity drop ]
77 [ [ other-body ] 2dip '[ body mass>> _ * _ n*v v+ ] change-velocity drop ] 2bi ;
79 : advance ( system dt -- )
81 [ '[ _ update-velocity ] [ drop ] each-pair ]
82 [ '[ _ update-position ] each ]
85 : inertia ( body -- e )
86 [ mass>> ] [ velocity>> norm-sq ] bi * 0.5 * ;
88 : newton's-law ( other-body body -- e )
89 [ [ mass>> ] bi@ * ] [ [ location>> ] bi@ distance ] 2bi / ;
91 : energy ( system -- x )
92 [ 0.0 ] dip bodies>> [ newton's-law - ] [ inertia + ] each-pair ; inline
96 [ energy . ] [ '[ _ 0.01 advance ] times ] [ energy . ] tri ;
98 HINTS: update-position body float ;
99 HINTS: update-velocity body body float ;
100 HINTS: inertia body ;
101 HINTS: newton's-law body body ;
102 HINTS: nbody fixnum ;
104 : nbody-main ( -- ) 1000000 nbody ;