public static long intersectionCount(DirectBitMap a, DirectBitMap b) {
        return BitUtil.pop_intersect(a.bitsBase, a.bitsAddr, b.bitsBase, b.bitsAddr, 0, Math.min(a.wlen, b.wlen));
    }
@param a The first set
@param b The second set
@return Returns the popcount or cardinality of the intersection of the two sets. Neither
set is modified.
indexr-common/src/main/java/io/indexr/util/DirectBitMap.java