if (StringUtil.isBlank(fessConfig.getIndexReindexRequestsPerSecond())) {
            return null;
        }
        final String value = fessConfig.getIndexReindexRequestsPerSecond();
        if ("adaptive".equalsIgnoreCase(value)) {
            if (fessConfig.availableProcessors() >= 4) {
                return null;
            }

      // Both a and b are odd. Assume a > b; then gcd(a - b, b) = gcd(a, b).
      // But in gcd(a - b, b), a - b is even and b is odd, so we can divide out powers of two.

      // We bend over backwards to avoid branching, adapting a technique from
      // http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax

      long delta = a - b; // can't overflow, since a and b are nonnegative