https://svn.boost.org/trac10/ticket/11167 <p> Userspace time exceeds wall time showing &gt;100% CPU utilization on OSX : 0.011577s wall, 0.020000s user + 0.000000s system = 0.020000s CPU (172.8%) </p> <p> I have not seen any fractional values for userspace time, it looks like it can only increase in 0.01s intervals causing the incorrect print out above. </p> <hr /> <p> #include &lt;iostream&gt; #include &lt;vector&gt; #include &lt;boost/timer/timer.hpp&gt; </p> <p> int main(int argc, const char * argv[]) { </p> <blockquote> <p> std::vector&lt;float&gt; hv( 1000*1000 ); { </p> <blockquote> <p> boost::timer::auto_cpu_timer t; std::generate(hv.begin(), hv.end(), rand); </p> </blockquote> <p> } return 0; </p> </blockquote> <p> } </p> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/11167 Trac 1.4.3