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> strip few least significant bits

I'm unconvinced. Doesnt this just replace the need to choose a suitable epsilon with the need to choose the right number of bits to strip? With the latter affording much fewer choices for degree of "roughness" than does the former.

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Not quite. It's basically a combined mantissa and exponent test, so it can be thought of as functionally equivalent to scaling epsilon by a power of two (the shared exponent of the nearly equal floating point values) and then using that epsilon.

I think I'll just use scaled epsilon... though I've gotten lots of performance wins out of direct bitwise trickery with floats (e.g., fast rounding with mantissa normalization and casting).

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