21–30 of 133 posts
The library is the real problem.
code.google.com/p/fridgescript - faster than C in some cases, only because it doesn't use the math library, but uses hardware without indirect calls and without caring for obscure edge cases.
C and C++ are efficient for general-purpose programming, if you know how to use them. C is here to stay because it is lingua franca of the computing world: OS APIs are defined in terms of C functions, and I know of no libraries in wide-spread use that do not offer a C or C++ interface. People otherwise rightfully challenge his conclusions. There's a funny comment there about matlab: "MATLAB struck me as being the wro…
I dare say this is more or less true of C, but following big improvements in the quality of C++ compilers (changes that happened well before 2006), C++ has proven itself as a language for high-performance scientific computing. Todd Veldhuizen provided a survey back in 1997 of the changing case in favour of C++ to accompany his Blitz C++ library: http://www.autistici.org/sens/inf/scientificcomputingcfortra...
Fortran still has considerable advantages, but it's been a long time since Fortran programmers could regard C++ as offering unserious performance.
I would also hesitate to say that C++ is lower level than Fortran. With a suitable coding style, C++ is a quite high-level language. In fact, it is precisely the abstractions that C++ offered (templates) that allow the optimisations to take place that have delivered these improvements in compiler performance. Was the author not aware that templates can be used in this way? The discussion of alias detection suggests so.
The high-level point is right, namely that abstractions make for safer languages and give compilers freedom to make optimisations that apparently more efficient, less safe languages cannot, and so deliver better performance. But it would have been a better article if it had not mentioned C++.
Another conclusion to draw is that benchmarks produced by people who are out to make a point are worthless.
This is old (2006), and seems to base its argument around the problems with unrestricted pointers in C, that cause aliasing. As of C99, of course, C has the "restrict" keyword which allows pointers to explicitly be declared to not alias, thus enabling all these optimizations in C, too.
At first I didn't include the date in the title, because I don't think it matters, the author's position seems even stronger now with many popular alternative languages, fast VMs and effective JIT compilers. Anyway, C99 was, of course, already 6-7 years old in 2006.
This is old (2006), and seems to base its argument around the problems with unrestricted pointers in C, that cause aliasing. As of C99, of course, C has the "restrict" keyword which allows pointers to explicitly be declared to not alias, thus enabling all these optimizations in C, too.
void f(char * restrict p, char * restrict q); char * h() { static char s[10]; return s; } void g() { f(h(), h()); }
(Correctness of a program using restrict is, in general, not decidable.)
The tradeoff here is that while restrict can be used to allow for further aliasing, it is very easy to write code with undefined behavior as a result. Dennis Ritchie argued as much when he (successfully) kept "noalias", the precursor of "restrict", out of the C89 standard: http://www.lysator.liu.se/c/dmr-on-noalias.html (while "restrict" is not quite as dangerous as "noalias", it still has to be used with care).
That suggests that at least circa 2004, if aliasing were a serious problem for C compilers, restrict annotations were not the solution, which calls Chu-Carroll's claim into question. But there might be other explanations. Any thoughts?
[1] http://blog.regehr.org/archives/537
ETA: Just to clarify what the 2004 paper involved: the researcher took the SPEC code and ran it through a dynamic analysis tool that identified every single use of non-restricted pointers that did not alias any other in-scope pointer at the time. He then took all of those pointers and marked them as restricted in the source text. The result was a program with every possible pointer marked as restricted that could be so marked. That's way more than a human annotater will ever do. And all that got him a 1% performance improvement.
A 5minute run-time in Python might be acceptable if it takes you 1 hour to write it and are only going to use it once; whereas you may not even know how to program in OCaml even though it offers the best run-time.
This is old (2006), and seems to base its argument around the problems with unrestricted pointers in C, that cause aliasing. As of C99, of course, C has the "restrict" keyword which allows pointers to explicitly be declared to not alias, thus enabling all these optimizations in C, too.
Thank you. I see some variant of this argument somewhere on the web every few months, and it makes me want to bang my head on the table.
This is old (2006), and seems to base its argument around the problems with unrestricted pointers in C, that cause aliasing. As of C99, of course, C has the "restrict" keyword which allows pointers to explicitly be declared to not alias, thus enabling all these optimizations in C, too.
However the article had been valid if it were published before C99.
Umm, yes C/C++ will not parallelize your code for you, whereas Language XYZ will. Im not sure how this is an argument against C/C++ being effective. C/C++ will not parallelize your code by design. It's was never meant to. I'd never blame my stick-shift car for not changing gears by itself - thats the first reason I didnt buy an automatic in the first place! If your matrix manupuilation code performance becomes an iss…