Brian Gough wrote:

> BUG#8 -- inexact coefficients in rk8pd.c

I finally got the reference article from Dormand and Prince (many thanks
again Joonas). In fact, the article itself gives these false
approximations and explicitly says "they were computed using a precision
of about 24 significant digits and the rationals presented in table 2
are continued fractions accurate to 18 significant figures".

I still think there is an error in the first and fourth elements of the
b7 array, but this error was in the original article. I also think the
real coefficients given in rksuite are more accurate, and since they
thank Dormand and Prince for their help, I think they got the original
coefficients from the authors. I don't know if all 30 significant
figures given in rksuite are good or if only the first 24 ones are good.

I will check this as time permit. For the moment, I propose the
following patch, which only add some comments (corected order of the
method, article reference) and correct two coefficients. I have just
written it now to answer this mail, not tried it (and even no compiled
it, so beware of typos ...)

                                                         Luc