CREATE EXTENSION popcount;
SELECT popcount(15::bit(4));
 popcount 
----------
        4
(1 row)

SELECT popcount(7::bit(4));
 popcount 
----------
        3
(1 row)

SELECT popcount(15::bit(8));
 popcount 
----------
        4
(1 row)

SELECT popcount(7::bit(8));
 popcount 
----------
        3
(1 row)

SELECT popcount(15::bit(12));
 popcount 
----------
        4
(1 row)

SELECT popcount(7::bit(12));
 popcount 
----------
        3
(1 row)

SELECT popcount(15::bit(32));
 popcount 
----------
        4
(1 row)

SELECT popcount(7::bit(32));
 popcount 
----------
        3
(1 row)

SELECT popcount(30::bit(32));
 popcount 
----------
        4
(1 row)

SELECT popcount(127::bit(32));
 popcount 
----------
        7
(1 row)

SELECT popcount(b'10101010101010101010101010101010101101010101010101010101010101010101011010101010101010101010101010101010110101010101010101010101010101010101101010101010101010101010101010101011010101010101010101010101010101010110101010101010101010101010101010101101010101010101010101010101010101011010101010101010101010101010101010110101010101010101010101010101010101101010101010101010101010101010101011010101010101010101010101010101010110101010101010101010101010101010101101010101010101010101010101010101011010101010101010101010');
 popcount 
----------
      263
(1 row)

SELECT sum(popcount(x::bit(512))) from generate_series(1,1000000) x;
   sum   
---------
 9884999
(1 row)

SELECT sum(popcount(x::bit(500))) from generate_series(1,1000000) x;
   sum   
---------
 9884999
(1 row)