On Wed, Aug 18, 2010 at 11:52 PM, <[email protected]> wrote: > On Wed, Aug 18, 2010 at 10:36 AM, Charles R Harris > <[email protected]> wrote: >> >> >> On Wed, Aug 18, 2010 at 8:25 AM, Colin Macdonald <[email protected]> >> wrote: >>> >>> On 08/18/10 15:14, Charles R Harris wrote: >>> > However, the various constants supplied by numpy, pi and such, are >>> > full precision. >>> >>> no, they are not. My example demonstrated that numpy.pi is only >>> double precision. >>> >> >> Hmm, the full precision values are available internally but it looks like >> they aren't available to the public. I wonder what the easiest way to >> provide them would be? Maybe they should be long double types by default? > > playing with some examples, I don't seem to be able to do anything > with longdouble on win32, py2.5
For all practical purposes, double == long double on windows: although some compilers support the intel long format or even quadd precision, the MSVC runtime does not (so you cannot print, scan, etc... making them useless). cheers, David > >>>> np.array([3141592653589793238L], np.int64).astype(np.longdouble)[0] > 3141592653589793300.0 >>>> np.array([3141592653589793238L], np.int64).astype(float)[0] > 3.1415926535897933e+018 >>>> 1./np.array([np.pi],np.longdouble)[0] - 1/np.pi > 0.0 >>>> 1./np.array([np.pi],np.longdouble)[0] > 0.31830988618379069 > > and it doesn't look like it's the print precision >>>> 1./np.array([np.pi],np.longdouble)[0]*1e18 > 318309886183790720.0 >>>> 1./np.array([np.pi],float)[0]*1e18 > 3.1830988618379072e+017 > > > type conversion and calculations seem to go through float > > Josef > >> >> Chuck >> >> >> _______________________________________________ >> NumPy-Discussion mailing list >> [email protected] >> http://mail.scipy.org/mailman/listinfo/numpy-discussion >> >> > _______________________________________________ > NumPy-Discussion mailing list > [email protected] > http://mail.scipy.org/mailman/listinfo/numpy-discussion > _______________________________________________ NumPy-Discussion mailing list [email protected] http://mail.scipy.org/mailman/listinfo/numpy-discussion
