colordifference_stdc: use float as in SSE #58
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The SSE implementation of the function uses single-precision float, whereas this one goes for.... double all over the place. Extremely unscientific comparisons on godbolt (https://gcc.godbolt.org/z/oa3hP5ffs) shows that both Clang and GCC do much better generating code when float is used.
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The SSE implementation of the function uses single-precision float, whereas this one goes for.... double all over the place.
Extremely unscientific comparisons on godbolt (https://gcc.godbolt.org/z/oa3hP5ffs) shows that both Clang and GCC do much better generating x64 code when float is used. Other SIMD systems should act similarly, but I can't remember the target names. (For more human-like code in clang, try
-Ofast. I could add an attribute or some assumes there, but ehhhh... sounds unnecessary.)PS: It might be a good idea to review other internal uses of
doubletoo. The two cases left appear to be generally sums and other statistics, which I guess is better withdouble, andgamma, which has an externaldoubleAPI.