Mon, 29 Sep 2008 12:33:32 +0200, Matthieu Brucher wrote: > 2008/9/29 Pauli Virtanen <[EMAIL PROTECTED]>: >> Mon, 29 Sep 2008 12:07:53 +0200, Matthieu Brucher wrote: >> >>>>>>> np.log(-1 + 0j) >>>> 3.1415926535897931j >>>>>>> np.log(-1 - 1e-99j) >>>> -3.1415926535897931j >>>>>>> np.log(-1 + 1e-99j) >>>> 3.1415926535897931j >>>> >>>> I'd guess this is typically harmless, but may lead to problems if >>>> your code relies on the choice of branch at the branch cut. >>>> >>>> Could you check if this is really the case? If log seems to work OK, >>>> then it's a problem with the test and not the functions. >>> >>> The result is what you expected. >> >> Do you mean that the problem is with the test, or with the branch cut >> of log? > > I don't know, but the results are : > >>>> np.log(-1 + 0j) > 3.1415926535897931j >>>> np.log(-1 - 1e-99j) > -3.1415926535897931j >>>> np.log(-1 + 1e-99j) > 3.1415926535897931j
Ok, then the problem must be that with ICC, numpy's log does not respect the negative zero in the imaginary part. On my platform, it does: >>> import numpy as np >>> x = 1 + 0j >>> np.log(-x) -3.1415926535897931j >>> np.log(-1 - 0j) 3.1415926535897931j So probably also this test should be marked as a known failure (for some platforms). But this is probably harmless anyway. -- Pauli Virtanen _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion