Torch7 Tensor version Laplace solver

laplace_torch.lua

require 'torch'

function calc(N, Niter)
   u = torch.zeros(N,N)
   u[1] = 1
   for i=1,Niter do
      lua_update(u)
   end
   return u
end

function lua_update(u)
   local dx = 0.1
   local dy = 0.1
   local dx2 = dx*dx
   local dy2 = dy*dy

   -- Assume u is square
   nx,ny = u:size(1), u:size(2)
   u[{ {2,nx-1}, {2,ny-1} }] = ((u[{ {3,nx},{2,ny-1} }] + u[{ {1,ny-2},{2,ny-1} }])*dy2 + (u[{ {2,nx-1},{3,nx} }] + u[{ {2,nx-1}, {1,ny-2} }]) * dx2) / (2*(dx2+dy2))

end

timer = torch.Timer()
u = calc(100,8000)
print(timer:time().real)
print(u[2][2])
print(torch.sum(u))