Hi Tuomo, Can you comment on the problem Andreas is experiencing with some ode-initval2 test cases?
>>> 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. >> 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. > This is the failure I get: > > gsl: msbdf.c:1336: ERROR: msbdf_apply too large order change > -- order change -2 > > This comes from test_extreme_problems, with the "ringmod" problem. > Enabling DEBUG in msbdf.c shows this difference between > -ffp-contract=off and -ffp-contact=fast: > > --- dstep: 9.81743e-17 3.08687e-48 9.07047e-10 -9.07047e-10 -9.07047e-10 > 9.07047e-10 -3.62750e-13 -2.20616e-27 -6.93678e-59 -1.81409e-16 -1.81409e-16 > 1.81409e-16 1.81409e-16 1.57079e-14 4.93899e-46 > +-- dstep: 9.81743e-17 -8.68549e-36 9.07047e-10 -9.07047e-10 -9.07047e-10 > 9.07047e-10 -3.62750e-13 -2.20616e-27 5.60182e-46 -1.81409e-16 -1.81409e-16 > 1.81409e-16 1.81409e-16 1.57079e-14 -1.96797e-42 I don't know that region of GSL well enough to understand the discrepancy between 3.08687e-48 and -8.68549e-36; -6.93678e-59 and 5.60182e-46; or 4.93899e-46 and -1.96797e-42. All of them seem like floating point noise near zero to me... - Rhys _______________________________________________ Bug-gsl mailing list [email protected] https://lists.gnu.org/mailman/listinfo/bug-gsl
