big.NewRat((1<<d)*int64(x), q) // (2ᵈ / q) * x == (2ᵈ * x) / q // FloatString rounds halves away from 0, and our result should always be positive, // so it should work as we expect. (There's no direct way to round a Rat.) rounded, err := strconv.ParseInt(precise.FloatString(0), 10, 64) if err != nil { panic(err) } // If we rounded up, `rounded` may be equal to 2ᵈ, so we perform a final reduction. return uint16(rounded % (1 << d)) } func TestCompress(t *testing.T) { for d := 1; d < 12; d++ { for n...