switch (bitwidth) {

case 1:

return {-0.7979f, 0.7979f};

case 2:

return {-1.5104f, -0.4528f, 0.4528f, 1.5104f};

case 3:

return {-2.1520f, -1.3439f, -0.7560f, -0.2451f,

0.2451f, 0.7560f, 1.3439f, 2.1520f};

case 4:

return {-2.7326f, -2.0690f, -1.6180f, -1.2562f,

-0.9424f, -0.6568f, -0.3881f, -0.1284f,

0.1284f, 0.3881f, 0.6568f, 0.9424f,

1.2562f, 1.6180f, 2.0690f, 2.7326f};

default:

throw std::invalid_argument("bitwidth must be 1-4, got " + std::to_string(bitwidth));

}

if (bitwidth < 1 || bitwidth > 4)

throw std::invalid_argument("bitwidth must be 1-4");

if (dim < 2)

throw std::invalid_argument("dimension must be >= 2");

auto centroids = normalized_centroids(bitwidth);

float scale = 1.0f / std::sqrt(static_cast<float>(dim));

for (auto& c : centroids)

c *= scale;

std::vector<float> boundaries;

boundaries.reserve(centroids.size() - 1);

for (std::size_t i = 0; i + 1 < centroids.size(); ++i)

boundaries.push_back(0.5f * (centroids[i] + centroids[i + 1]));

return ScalarCodebook{

.bitwidth = bitwidth,

.num_centroids = static_cast<int>(centroids.size()),

.centroids = std::move(centroids),

.boundaries = std::move(boundaries),

};