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This was a seperate repository in CVS and so it missed the conversion.
benchmarks/
As above.
50 lines
1.6 KiB
Haskell
50 lines
1.6 KiB
Haskell
--
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-- Patricia Fasel
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-- Los Alamos National Laboratory
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-- 1990 August
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--
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module ChargeDensity (chargeDensity) where
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import PicType
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import Consts
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import Data.Array
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-- Phase I: calculate the charge density rho
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-- Each particle represents an amount of charge distributed over an entire cell.
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-- In discretizing the charge density at the grid points we split the cell into
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-- four rectangles and assign to each corner an amount of charge proportional
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-- to the area of the opposite diagonal sub rectangle
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-- So each particle contributes a portion of charge to four quadrants
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-- particle position is (i+dx, j+dy)
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-- nw quadrant (1-dx)(1-dy)(charge) is added to rho(i,j)
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-- ne quadrant (dx)(1-dy)(charge) is added to rho(i,j+1)
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-- sw quadrant (1-dx)(dy)(charge) is added to rho(i+1,j)
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-- se quadrant (dx)(dy)(charge) is added to rho(i+1,j+1)
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-- wrap around used for edges and corners
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chargeDensity :: ParticleHeap -> Rho
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chargeDensity (xyPos, xyVel) =
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accumArray (+) 0 ((0,0), (n,n)) (accumCharge xyPos)
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where
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n = nCell-1
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-- for each particle, calculate the distribution of density
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-- based on (x,y), a proportion of the charge goes to each rho
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accumCharge :: [Position] -> [MeshAssoc]
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accumCharge [] = []
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accumCharge ((x,y):xys) =
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[((i ,j ) , charge * (1-dx) * (1-dy))] ++
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[((i',j ) , charge * dx * (1-dy))] ++
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[((i ,j') , charge * (1-dx) * dy)] ++
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[((i',j') , charge * dx * dy)] ++
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accumCharge xys
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where
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i = truncate x
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i' = (i+1) `rem` nCell
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j = truncate y
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j' = (j+1) `rem` nCell
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dx = x - fromIntegral i
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dy = y - fromIntegral j
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