WIAS Preprint No. 1305, (2008)

Fast, stable and accurate numerical method for the Black--Scholes equation of American options


  • Ehrhardt, Matthias
  • Mickens, Ronald

2010 Mathematics Subject Classification

  • 35A35 65N99 91B26


  • Black-Scholes equation, computational finance, option pricing, finite difference method, artificial boundary condition, free boundary problem, American option




In this work we improve the algorithm of Han and Wu (SIAM J. Numer. Anal. 41 (2003), 2081-2095) for American Options with respect to stability, accuracy and order of computational effort.
We derive an exact discrete artificial boundary condition (ABC) for the Crank-Nicolson scheme for solving the Black-Scholes equation for the valuation of American options. To ensure stability and to avoid any numerical reflections we derive the ABC on a purely discrete level.
Since the exact discrete ABC includes a convolution with respect to time with a weakly decaying kernel, its numerical evaluation becomes very costly for large-time simulations. As a remedy we construct approximate ABCs with a kernel having the form of a finite sum-of-exponentials, which can be evaluated in a very efficient recursion. We prove a simple stability criteria for the approximated artificial boundary conditions.
Finally, we illustrate the efficiency and accuracy of the proposed method on several benchmark examples and compare it to previously obtained discretized ABCs o f Mayfield and Han and Wu.

Appeared in

  • Int. J. Theor. Appl. Finance, 11 (2008) pp. 471--501.

Download Documents