32 lines
1.1 KiB
Haskell
32 lines
1.1 KiB
Haskell
{-# LANGUAGE ParallelListComp #-}
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import Numeric.LinearAlgebra (linearSolve, toDense, (!), flatten)
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import Data.Monoid ((<>), Sum(..))
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rMesh n (ar, ac) (br, bc)
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| n < 2 = Nothing
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| any (\x -> x < 1 || x > n) [ar, ac, br, bc] = Nothing
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| otherwise = between a b <$> voltage
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where
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a = (ac - 1) + n*(ar - 1)
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b = (bc - 1) + n*(br - 1)
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between x y v = abs (v ! a - v ! b)
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voltage = flatten <$> linearSolve matrixG current
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matrixG = toDense $ concat [ element row col node
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| row <- [1..n], col <- [1..n]
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| node <- [0..] ]
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element row col node =
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let (Sum c, elements) =
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(Sum 1, [((node, node-n), -1)]) `when` (row > 1) <>
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(Sum 1, [((node, node+n), -1)]) `when` (row < n) <>
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(Sum 1, [((node, node-1), -1)]) `when` (col > 1) <>
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(Sum 1, [((node, node+1), -1)]) `when` (col < n)
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in [((node, node), c)] <> elements
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x `when` p = if p then x else mempty
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current = toDense [ ((a, 0), -1) , ((b, 0), 1) , ((n^2-1, 0), 0) ]
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