A-Stable Composite Multistep Methods

  • Authors:
  • Harry M. Sloate;Theodore A. Bickart

  • Affiliations:
  • General Electric Electronics Laboratory, Electronics Park 3-120, Syracuse, New York;Department of Electrical and Computer Engineering, 111 Link Hall, Syracuse University, Syracuse, New York

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 1973

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Abstract

Consider the set of multistep formulas ∑l-1jmn-k &agr;ijxmn+j - h ∑l-1jmn-k&bgr;ijxmn+j = 0, i = 1, ···, l, where xmn+j = ymn+j for j= -k, ···, -1 and xn = ƒn = ƒ(xn , tn). These formulas are solved simultaneously for the xmn+j with j = 0, ···, l - 1 in terms of the xmn+j with j = -k, ··· , - 1, which are assumed to be known. Then ymn+j is defined to be xmn+j for j = 0, ··· , m - 1. For j = m, ··· , l - 1, xmn+j is discarded. The set of y's generated in this manner for successive values of n provide an approximate solution of the initial value problem: y = ƒ(y, t), y(t0) = y0. It is conjectured that if the method, which is referred to as the composite multistep method, is A-stable, then its maximum order is 2l. In addition to noting that the conjecture conforms to Dahlquist's bound of 2 for l = 1, the conjecture is verified for k = 1. A third-order A-stable method with m = l = 2 is given as an example, and numerical results established in applying a fourth-order A-stable method with m = 1 and l = 2 are described. A-stable methods with m = l offer the promise of high order and a minimum of function evaluations—evaluation of ƒ(y, t) at solution points. Furthermore, the prospect that such methods might exist with k = 1—only one past point—means that step-size control can be easily implemented