“…In spite of its great cost, this option is widely used with radial basis functions (RBF) because of its simplicity. A much faster procedure is to use a so-called Fast Summation to sum RBF series and a preconditioned iteration, repeatedly calling a Fast Summation routine, for interpolation [98,26]. Because these routines are complicated, they are not yet widely used with RBFs, so Table 7 lists the costs for both direct and iterative RBF interpolation.…”