> -----Original Message----- > From: Martin Sebor [mailto:[EMAIL PROTECTED] On Behalf Of Martin Sebor > Sent: Monday, June 30, 2008 10:51 PM > To: dev@stdcxx.apache.org > Subject: Re: implementation of Unary Traits > > Travis Vitek wrote: > > > [...] > > If you ask what I prefer, I'm going to tell you I prefer the second > > option (that is essentially what I wrote originally). But, > honestly, for > > me to care either way, I need to know that there actually a > noticeable > > performance difference between the two techniques. > > FYI: I used gcc 4.3 and EDG eccp to measure the difference between > the compilation times of each of the two approaches (i.e., using > specialization vs using remove_cv). > > In a program involving 10,000 invocations of is_void on distinct > types, the specialization approach was 5 and 10 times faster than > the one using remove_cv when using gcc and eccp, respectively. In > the same program using only 1000 types, the specialization solution > compiled 2 and 3 times faster, respectively. > > With gcc, the compiler also required about half the amount of system > memory to compile the specialization-based solution than the other > one. (I didn't measure eccp memory usage). > > This confirms that template metaprogramming is significantly more > costly in terms of system resources than alternative approaches, > at least in the gcc and eccp implementations. We should re-run the > same tests with other compilers to get a complete picture.
That's not unexpected: like everything in computing, it's a tradeoff. To get a really complete picture, you'd have to compare the metaprogramming approach to the run-time alternatives. I would expect to see a corresponding speed increase and storage savings compared to the runtime counterparts. Brad.
