EIKONAL THEORY AND COMPUTER ALGEBRA .2.

The computer routine used in a previous paper [J. Opt. Sec. Am. A 13, 523 (1996)] for the concatenation of eikonals is quite slow in certain demanding cases. This problem can be overcome by using the order doub ling technique developed for this purpose by Forbes [J. Opt. Sec. Am. 72, 1097 (1982); 73, 782 (1983)] and Forbes and Andrews [J. Opt. Sec. Am. 73, 776 (1983)] more than a dozen years ago. Numerical experiments show that this technique speeds up the calculations by two orders of magnitude or more. (C) 1996 Optical Society of America.