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-ffast-math

A compiler flag that lets the compiler treat floats as if they were real numbers (regroup, assume no NaN or infinity) for speed, at the cost of exact IEEE results.

GCC/Clang -ffast-math enables reassociation, assumes no NaNs or infinities, allows reciprocal approximations and contraction, and may set flush-to-zero at startup; MSVC's nearest equivalent is /fp:fast.

See also

reassociation Kahan summation NaN
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