Function sign_pack

nodedb-codec/src/vector_quant/rabitq.rs:90–99

Pack `dim` signs from `rotated` (negative = 1-bit, non-negative = 0-bit) into ceil(dim/8) bytes, LSB-first.

(rotated: &[f32], dim: usize)

/// Pack `dim` signs from `rotated` (negative = 1-bit, non-negative = 0-bit)
/// into ceil(dim/8) bytes, LSB-first.
fn sign_pack(rotated: &[f32], dim: usize) -> Vec<u8> {
    let nbytes = dim.div_ceil(8);
    let mut out = vec![0u8; nbytes];
    for (i, &v) in rotated.iter().take(dim).enumerate() {
        if v < 0.0 {
            out[i / 8] |= 1 << (i % 8);
        }
    }
    out
}

/// Dequantize sign-packed bits back to ±1 values (for dot_quantized calc).
fn sign_unpack(packed: &[u8], dim: usize) -> Vec<f32> {