@Override
    public double asDouble() {
        // Hash using the xxh3 algorithm which is also used on content nodes
        byte[] data = value.getBytes(StandardCharsets.UTF_8);
        long h = Hasher.xxh3(data);
        if ((h & 0x7ff0000000000000L) == 0x7ff0000000000000L) {
            // Avoid nan and inf
            h = h & 0xffefffffffffffffL;
        }
        return Double.longBitsToDouble(h);
    }
Returns the XXHash hashcode of this, to enable strings to be encoded (with reasonable safely)
as doubles for optimization.
searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/StringValue.java