------- Comment #13 from sgk at troutmask dot apl dot washington dot edu 2009-09-11 20:26 ------- Subject: Re: VOLATILE in Fortran does not take effect
> > What is your hardware? x86 or something else? Opteron. > I have Atlon 2000 MP and Intel Quad and on both of these systems I get > differences in output for "real" and "double precision". > > What I can do to prove that I do have differences and what to do to find out > why? > Have you tried -ffloat-store? This should save/load a FPU register after every operation. There is the -fpmath= option, but I'm not sure which switches are appropriate for your cpu. There is also the -msse set of options. To find out why you have differences, print out intermediate values to 16 and 7 significant figures for real and double precision. It may also be helpful to read Goldberg's paper if you haven't (see the gfortran wiki, manuals section). -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41335
