scijs / ndarray-stencil

Stencil operators for ndarrays

ndarray-stencil

Stencil iterators for ndarrays. This code can be used to implement things like cellular automata or various PDE operations on ndarrays.

Example

var zeros = require("zeros")

var points = [[-1, 0], [1, 0], [0,-1], [0, 1]]

var diffuse = require("ndarray-stencil")(points, function(a, b, c, d) {
  return 0.25 * (a + b + c + d)
})

var x = zeros([5,5])
var y = zeros([5,5])

x.set(2,2,1)

diffuse(y, x)

//Now:
//
// y =[ [ 0, 0,    0,    0,    0 ],
//      [ 0, 0,    0.25, 0,    0 ],
//      [ 0, 0.25, 0,    0.25, 0 ],
//      [ 0, 0,    0.25, 0,    0 ],
//      [ 0, 0,    0,    0,    0 ] ]

Install

npm install ndarray-stencil

require("ndarray-stencil")(points, stencil_func[, options])

Creates a stencil operator for an ndarray.

• points is a list of points that the stencil will be evaluated on
• stencil_func(...) is a function that takes in n arguments, where n is the number points to evaluate the stencil on, and returns the new value of the grid on the given point.
• options is an object containing a list of optional properties:
  • useIndex If this flag is set, add an extra index parameter as the last argument to stencil_func. (Default false)
  • sameOutput if set, then the output is not sliced and instead the result of the stencil operation is applied directly to output

Returns A function that applies the stencil to two arrays. The first argument is the output array, and the second is the input.

Credits

(c) 2013 Mikola Lysenko. MIT License

ndarray-stencil's Issues

Mixing ndarray-proxy and ndarray-stencil

I ended up taking the proxy approach for combining ndarrays, but bumped into an issue when applying ndarray-stencil to a proxy. Specifically, I managed to track the problem down to creating new instances of the array in the generated _stencil_wrapper, e.g.:

var out_c = out.constructor
var inp_c = inp.constructor

func(
  new out_c(
    out_d,
    nshape,
    out_s,
    out_o + out_s[0] + out_s[1] | 0
  ),
  new inp_c(
      inp_d
    , nshape
    , inp_s
    , inp_o | 0
  )
)

This works fine with a normal ndarray, but in my case I end up getting an empty proxy. Would you have any ideas on how to work around the issue, either by changing one of the modules or my own code?

Thanks again :)