Function Order3

src/OpenColorIO/ops/lut1d/Lut1DOpCPU.cpp:727–744

Compute the indices for the smallest, middle, and largest elements of RGB[3]. (Trying to be clever and do this without branching.)

// Compute the indices for the smallest, middle, and largest elements of
// RGB[3]. (Trying to be clever and do this without branching.)
inline void Order3(const float* RGB, int& min, int& mid, int& max)
{
    //                                    0  1  2  3  4  5  6  7  8  (typical val - 3)
    static const int table[] = { 2, 1, 0, 2, 1, 0, 2, 1, 2, 0, 1, 2 };

    int val = (int(RGB[0] > RGB[1]) * 5 + int(RGB[1] > RGB[2]) * 4)
              - int(RGB[0] > RGB[2]) * 3 + 3;

    // A NaN in a logical comparison always results in False.
    // So the case to be careful of here is { A, NaN, B } with A > B.
    // In that case, the first two compares are false but the third is true
    // (something that would never happen with regular numbers).
    // So that is the reason for the +3, to make val 0 in that case.

    max = table[val];
    mid = table[++val];
    min = table[++val];
}
};