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Roberto Ierusalimschy <roberto@inf.puc-rio.br> writes:
> This result is correct. On many (all?) Intel CPUs, long double uses
> 80-bit floats, which have exactly 64 bits in their mantissas. So, they
> count correctly up to 2^64, but after that they lose precision. (Because
> of alignment, the sizeof of a long double usually is larger than 80
> bits.)

BTW, another issue with long floats on x86-family processors is that
they're not supported by SSE instructions, only by the 387 FPU
instructions, and my understanding is that the latter tend to be
slower...

-miles

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