private static int getLinearCountingThreshold(int precision) {
        switch (precision) {
            case 4:
                return 10;
            case 5:
                return 20;
            case 6:
                return 40;
            case 7:
                return 80;
            case 8:
                return 220;
            case 9:
                return 400;
            case 10:
                return 900;
            case 11:
                return 1800;
            case 12:
                return 3100;
            case 13:
                return 6500;
            case 14:
                return 11500;
            case 15:
                return 22000;
            case 16:
                return 50000;
            case 17:
                return 120000;
            case 18:
                return 350000;
            default:
                // Unreachable code.
                throw new RuntimeException();
        }
    }
Estimates the number of unique elements.

@param sketch A sketch populated with values from the aggregation phase of HLL.
@return The estimated number of unique elements.
searchlib/src/main/java/com/yahoo/searchlib/aggregation/hll/HyperLogLogEstimator.java