[Bug fortran/33698] FAIL: gfortran.dg/gamma_5.f90

[dave at hiauly1 dot hia dot nrc dot ca]

------- Comment #17 from dave at hiauly1 dot hia dot nrc dot ca  2007-11-03 22:49 -------
Subject: Re:  FAIL: gfortran.dg/gamma_5.f90

> > Now, the hard part.  The gfortran.dg/gamma_5.f90 test fails at n = 16.
> 
> This works on my i686-pc-linux-gnu system, and also fails when I use
> -ffloat-store.  Seems like we have a roundoff problem with normal ieee
> double precision.
> 
> I'll continue to work on it...

Looking at Pugh's paper, he shows coefficients for n = 10 and
r = 10.900511.  This is the same as you are using for the double
case.  However, you seem to be missing coefficient d10.  I believe
that Pugh's coefficients and your coefficients should differ by
the factor

     2 * sqrt (e / pi) * exp (r)

due to Toth's rearrangement of the approximation.  This should
provide a check for your coefficient calculation.

Dave


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33698