Hi Andreas, On Sat, Nov 26, 2011 at 6:12 PM, Andreas Schwab <[email protected]> wrote: > The algorithms in cblas (at least) become instable when the compiler is > allowed to contract floating-point expressions. This manifests in the > failure of the ode-initval2 test. Add a configure check to disable fp > contractions.
When you say "instable" do you mean that they fail at some particular tolerance level? Could you give an example? The problem you describe sounds like overly-sensitive unit tests rather than a reason to entirely avoid FMAs. FWIW, I am aware of FMA gives the wrong answer for comparisons like (a*x + b*y) == 0 when x == y and b == -a. The fix is never check strict equality for floats and instead check if |a*x + b*y| < tol. The problem in those cases is not the use of FMAs but rather the code being incorrect in the presence of floating point arithmetic. - Rhys _______________________________________________ Bug-gsl mailing list [email protected] https://lists.gnu.org/mailman/listinfo/bug-gsl
