🚀 go-pugleaf

In article 199@comp.compilers, dodd@mycenae.cchem.berkeley.edu (Lawrence R. Dodd) writes:
>"Steve" Stevenson <steve@hubcap.clemson.edu> writes:
>> I am trying to make a catalog of folk wisdom in fortran programming.
>
>My personal favorite is the one discussed on page 137 of the 1st edition of
>Numerical Recipes (Fortran edition, of course):
>
>BAD
>
>P = c(1) + c(2)*x + c(3)*x**2 + c(4)*x**3 + c(5)*x**4
>
>GOOD
>
>P = c(1) + x*(c(2) + x*(c(3) + x*(c(4) + x*c(5))))
>
>It is a little harder to read but you won't be `summarily executed'

I hope that you don't mean folk wisdom in the sense of things that are
widely believed without justification: there is a good reason for
preferring the latter version.  The former version requires 4
additions, 4 multipications and 3 applications of the power operator
(should total 15 or 16 fp operations using an efficient algorithm for
raising fp numbers to integer powers.  The latter version does not
require application of the power operator.  Not only will it be
approximately twice as fast but it will accumulate less rounding
error.

	Chris Flatters
	cflatter@nrao.edu