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Abelian sandpile model: Difference between revisions
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sandpile with 100000 grains of sand: <tt>test 150 100000</tt>: [http://commons.wikimedia.org/wiki/File:Sandpile_150_100000.jpg]<br>
sandpile with 1000000 grains of sand: <tt>test 400 1000000</tt>: [http://commons.wikimedia.org/wiki/File:Sandpile_400_1000000.jpg]<br>
=={{header|J}}==
<lang J>
NB. have 2d grid. piles (x,y) with >= 4 units of sand spill over to
NB. neighbors.
NB. grid with x units of sand in center of grid of size y. y may be a
NB. single number in which case the grid is square or a 2-array with
NB. the dimensions y0 y1. assert that there's enough space to
NB. converge.
grid=: dyad define
assert. x < */ 4,2$y
x (<2$<.-:y)} (2$y)$0
)
NB. the current sand matrix is added with the change in sand by hook.
NB. the change is _4 at all the locations with 4&<:, plus the spilled
NB. sand from rotating (|.) by neighborhood _2 ]\ _1 0 0 _1 1 0 0 1
NB. and adding (+/).NB. this implementation has the grid wrapping around
NB. so that sand on the top may spill to the bottom. the fit conjunction
NB. |.!.0 could be used if sand should spill off the world instead.
sand=: +[:(_4&* + [: +/ (_2]\_1 0 0 _1 1 0 0 1)&|.) 4&<:
NB. reach a fix point (^: _) and display the sand using viewmat.
require 'viewmat'
spill=: [: viewmat sand ^: _
NB. if in jqt use viewmat to display an abelian sandpile.
spill ^: IFQT 256 grid 11
=={{header|Julia}}==
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