Re: C++ Speed Vs. Java

"James Kanze" <>
Mon, 22 Jan 2007 20:57:09 CST
Peter Dimov wrote:

James Kanze wrote:

Seweryn Habdank-Wojew?dzki wrote:

So why do you spending so much time for advocating JVM's performance?

I don't. I simply correct the mistaken view that C++ is
necessarily faster than Java in all cases, because Java uses a
VM, and C++ doesn't. (Formally, this isn't even a relevant
argument, because the Java specification allows for full static
compilation, and the C++ specification certainly doesn't forbid
the use of a VM.)

Java and C++ should be about equal in performance in a fair benchmark.
Unfortunately, most real C++ code that is performance sensitive is
unfair. It can go outside the C abstract machine by using, for example,
_m_paddusb in a few key places. :-)

I suspect that in a performance sensitive application, where you
invest the man/months necessary to get the maximum performance,
C++ will generally be faster, simply because it offers more
alternatives to experiment with. More importantly, IMHO, the
techniques necessary to get maximum performance from Java (using
arrays of basic types, to avoid the extra allocations and
indirection) break encapsulation.

James Kanze (GABI Software)
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