Re: Why use C++ instead of Java?
On Sep 7, 9:05 am, SG <s.gesem...@gmail.com> wrote:
On 7 Sep., 08:26, "Chris M. Thomasson" wrote:
[...]
For the most part it's a QoI issue (quality of implementation)
and not really related to the programming language. Why should
the C++ version of dynamically allocating many small objects
be slower than the Java version?
Because C++ implementations use a much older allocator, designed
for C, and for allocating fewer, larger objects. Because of
Java's design, Java programs usually do allocate a lot of small
objects with a short lifetime, enough so that allocator
performance becomes a major issue, and the allocators have been
optimized.
If you want to do a real comparison, try simulating some more
typical use: say allocate a 100 objects up front, then randomly
allocate and free (skipping the free in Java, of course), and
don't forget to free at the end of the C++ as well. You might
want to vary the size of the objects as well. And of course,
you'll definitely want to allocate enough so that the garbage
collector will run in Java---otherwise, Java will show up
unrealistically fast.
Also, of course, you'll want to dimension the test so that it
takes something around 5 minutes, to ensure that you aren't
being mislead by the granularity of your timers, and to make the
start up time of Java negligible (since we want to measure
allocation times, and not start-up time).
--
James Kanze