Defined in header <ctime>
#define CLOCKS_PER_SEC /*implementation defined*/
Expands to an expression (not necessarily a compile-time constant) of type std::clock_t equal to the number of clock ticks per second, as returned by clock().
POSIX defines CLOCKS_PER_SEC as one million, regardless of the actual precision of std::clock.
 See also
| returns raw processor clock time since the program is started
| process running time