For a fixed number of input points, the time varies in direct proportion to the number of output points; for a fixed number of output points, the time varies in direct proportion to the number of input points.
In the default case, all input points are used in forming the weighted average used in computing a given interpolated value. Execution time can be improved if you restrict yourself to using the number of input data values points within a fixed distance of the points where interpolated values are desired. The parameter to use to specify this fixed distance is dmx.
For the same number of input and output points, using the Dsgrid entries for interpolation at individual points invokes about a 30% overhead compared to using the Dsgrid entries to interpolate on a grid.