On 10/04/12 22:41, Liviu Nicoara wrote:
On 10/4/12 10:10 PM, Liviu Nicoara wrote:


On 10/3/12 11:10 AM, Martin Sebor wrote:
On 10/03/2012 07:01 AM, Liviu Nicoara wrote:

   void* thread_func (void*) {
       for (int i = 0; i < N; ++)
           test 1: do some simple stuff inline
           test 2: call a virtual function to do the same stuff
           test 3: lock and unlock a mutex and do the same stuff
   }

Test 1 should be the fastest and test 3 the slowest. This should
hold regardless of what "simple stuff" is (eventually, even when
it's getting numpunct::grouping() data).

That is expected; I attached test case x.cpp and results-x.txt.

I did not find it too interesting in its own, though. The difference
between the
cached and non-cached data is that in the case of the cached data the
copying of
the string involves nothing more than a bump in the reference counter,
whereas
in the non-cached version a string object is constructed anew, and
memory gets
allocated for its body. Yet, in my measurements, the cached version is
the one
which shows the worse performance.

So, I extracted the std::string class and simplified it down and put
it in
another test case. That would be u.cpp and the results are
results-u.txt. The
results show the same performance trends although the absolute values
have
skewed. Will get back to this after I digest the results a bit more.

This discussion has stagnated lately. I hope to allocate some time this week-end to go over the results, re-verify them and analyze the disassembly. In the meantime, any thoughts?

Liviu

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