On Tue, Jul 29, 2008 at 8:38 AM, Pauli Virtanen <[EMAIL PROTECTED]> wrote:
> Tue, 29 Jul 2008 08:13:23 -0600, Charles R Harris wrote: > [clip] > > We also need speed. I think we just say behaviour on the branch cuts is > > undefined, which is numerically true in any case, and try to get the > > nan's and infs sorted out. But only if the costs are reasonable. > > Well, the branch cut tests have succeeded on all platforms so far, which > means the behavior is numerically well-defined. I doubt we can lose any > speed by fixing sqrt in this respect. > Because of the discontinuity, roundoff error makes the behaviour undefined. It's just a fact of computational life. I suspect we mean slightly different things by "numerically" ;) Chuck
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