[eigen] Why BTL measures CPU time?

[ Thread Index | Date Index | More lists.tuxfamily.org/eigen Archives ]

I was looking into the BTL because I had a problem with the
benchmarks: all the multi-threaded libraries that I tested seemed to
be slower than the respective single-threaded counterparts (e.g. atlas
VS atlas-threads, openblas VS openblas-threads,...).

So I discovered that the BTL, within the Portable_Timer is measuring
the CPU time, not the wall-clock time. This means that in the
multi-threaded case all the CPU times of the threads were summed
together, resulting in no advantage of using many threads, but rather
a disadvantage because of the overhead. Nevertheless, when benchmarked
against the wall-clock time the multi-threaded implementations are
actually faster. Why is the CPU time measured?

Best regards
Andrea Arteaga

Mail converted by MHonArc 2.6.19+ http://listengine.tuxfamily.org/