NaN * 0 = 0

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NaN * 0 = 0

Postby fkluknav » Tue Feb 04, 2014 11:12 am


dgemm and many other functions assume 0 * anything = 0. They explicitly check for 0 and skip computations in that case. The obvious benefit is speed. The downside is when the matrix contains a NaN, this NaN is hidden and ignored. IEEE 754 says 0 * NaN = NaN. Some mathematical programs refuse to compile and install when they discover this during self-tests.
Does LAPACK strive for IEEE 754 compliance? Is this a bug or a feature?

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