On Tuesday, November 4, 2014 9:58:54 PM UTC+1, Thierry wrote: > > Hi, > > all those numerical noise appearing suddenly, couldn't that mean that > some numerical algorithm became less stable/accurate somewhere in the > code ? > > I think its the way we treat tolerance which changed, so no real problem hidden here .
If it turns out to be the case, we should thank doctests for the > discovery, not asking them to shut up by enlarging the tolerance ! > > Also, in the case where the error is just "going the other way", we > should not enlarge the tolerence, but instead have an exact expected > result in the doctest. For example, (see #17291): > > On Tue, Nov 04, 2014 at 05:15:29PM +0000, John Cremona wrote: > > File "src/sage/tests/french_book/linsolve_doctest.py", line 51, in > > sage.tests.french_book.linsolve_doctest > > Failed example: > > x = A\b; x # rel tol 1e-15 > > Expected: > > (-0.20000000000000018, 0.9000000000000001) > > Got: > > (-0.19999999999999987, 0.8999999999999999) > > Tolerance exceeded in 1 of 2: > > -0.20000000000000018 vs -0.19999999999999987, tolerance 2e-15 > > > 1e-15 > > We should expect (-0.2, 0.9) with the previous tolerance instead of > enlarging the tolerance (therefore weakening the doctest) with an > inexact expected result, since the errors are of the same magnitude but > not the same direction. > > The same holds for, for example (see #17278): > > On 04/11/2014 14:16, John Cremona wrote:> It's a long time since I have > > File "src/sage/matrix/matrix_double_dense.pyx", line 87, in > > sage.matrix.matrix_double_dense. > > Matrix_double_dense > > Failed example: > > m^(-1) > > Expected: > > [-1.9999999999999996 0.9999999999999998] > > [ 1.4999999999999998 -0.4999999999999999] > > Got: > > [-2.0 1.0] > > [ 1.5 -0.5] > > Enlagring the tolerance for catching the correct result instead of > taking this correct result as the centered expectation looks like an odd > fix ! > > Sure putting exact values as the centered ones is the best way to go. -- You received this message because you are subscribed to the Google Groups "sage-release" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-release. For more options, visit https://groups.google.com/d/optout.
