Tuesday, 26 February 2008

Rentree plus Some Comments on Google-Solvers & Co

Hi everybody! I'm back from my travels and can write some more blog-gobbledegook again (which I'll gladly do). I was away for some serious off-piste skiing in St.Anton, descending some pretty steep, big faces, and taking my first pinwheel tumble on a 40 degrees, Alaska-like, highly exposed, rock-fringed slope. Whow! And then I was back in town, and procuring my next project in just 2 days, taking a head-first plunge here as well ;-).

So let me start my rentree into the blogosphere with something less exciting, i.e. some comments on my previous posts. In fact, I wanted to comment on the Google-Solvers post for quite a long time, so it suits me fine.

Commenting on Java vs. C++

As some of you maybe remember, in a previous post* I compared the perfomance of Python, Perl, Java and C++ (admittedly in a rather ad-hoc manner), and made at first the error of not using the optimization switch of my C++ compiler. Me, a die-hard C++ hacker!!! This resulted in Java and C++ being on par performance-wise. So you can imagine my amazement some time ago when I saw in Uncle Bob's blog these statements**:

You can blame this on the non-optimized gcc compiler I was using (cygwin) but again: Oh boo hoo!. If there are any C++ programmers out there who smirk at the supposed slowness of Java, I think you'd better reconsider.
I'll grant you that the JVM can be large. However, if you assume it's already there, then the size of the bytecodes for the application itself need not be very large at all. And the heap can be constrained to a relatively small size to prevent virtual memory thrashing. So, if _engineered_ a java app should give a C++ app a run for it's money in most cases. -UB

Well, this started me thinkig. When you are looking for information concerning Java performance, you can see some typical quotes like this on the web ***:

John Davies: It is just the main reason why there are still diehards that stick with C/C++ because you can guarantee performance, not necessarily faster, but it just guarantees the performance and we will run something in Java, it will run quite frequently faster on C [he means JVM] than it would have done in C/C++, but every now and then it will just pause and that pause can be extremely expensive.
If you'll allow a small comment (hypothesis?, heresy?) from yours truly: what if all those measurements are done without the -O2 switch? It's an all to easy trap to fall into (see my own sufferings*) and an excellent opportunity for the marketing people to use some techniques from the seminal book "How to Lie with Statistics" ;-). Becuse you really can't explain to me that a language which is: 1. interpreted, 2. relies heavily on dynamic memory allocation, and 3. supports garbage collection, can be faster than one which doesn't do it, no matter how much optimization you throw at it! Or can you? If you've read the "Discipline of Programming" book of E. Dijkstra, you know that the first law he establishes there is the "there-are-no-miracles law" :-). So you may guess my position on this.

BTW, maybe I (or someone else) should email Mr. Stroustrup on this one, and see what he's got to say. It would be interesting, I guess, so maybe I'll do it anyway.

And now more comments

Let's continue in the commenting vein: sometime ago I was looking for web-frameworks in C++, and wanted even reimplement Java's Servlet classes in C++ (well, I didn't...). But in the last DDJ I saw an article**** about a C++ web-framework at last! Fortunately, I didn't implement the C++ servlet classes, because it was a really stupid idea! The Wt-framework ("witty" - http://www.webtoolkit.eu/wt/) seems to be rather like modern Java frameworks - GWT, ThinWire or Wicket - you define your application classes in C++, and the HTML rendering comes from the framework! In contrast to the Servlet specification, which is very low level and which nobody uses directly now! Thank God I was lazy! I'll have to try Wt out, perhaps there is an C++ alternative for web-programming anyway.

* http://ib-krajewski.blogspot.com/2007/07/google-solvers.html
** here he did basically the same but with Ruby in place of Python: http://butunclebob.com/ArticleS.UncleBob.SpeedOfJavaCppRuby
*** "Improving JVM scalability and performance": http://blog.chinaunix.net/u1/45382/showart_356477.html or http://go.techtarget.com/r/1950475/6108168
**** "Wt: A Web Toolkit": http://www.ddj.com/cpp/206401952