Java faster than C

http://paulbuchheit.blogspot.com/2007/06/java-is-faster-than-c.html

by Sam_Odio • 19 years ago

23 16 19 years ago

paulbuchheit.blogspot.com

gibsonf1• 19 years ago

It's nice to see SBCL Common Lisp tying for top speed honors with C :)

http://news.ycombinator.com/comments?id=26136

nickb3• 19 years ago

That's my experience with Java as well. Also, Java is much faster tan C++. C++ is slower than C.

Here's an interesting link: http://kano.net/javabench/

"JVM startup time was included in these results. That means even with JVM startup time, Java is still faster than C++ in many of these tests."

tx2• 19 years ago

C++ slower than C? Isn't that the same thing? Most of the time when I hear "C++ is slow" it usually means someone ran into slow STL+compiler combination. And according to my knowledge GCC is the worst performing compiler out there when it comes to optimizations. BY FAR. Intel and MSVC++ 7.1 eat it for breakfast, even with microsoft's profile-guided optimization turned off.

And by the way, why is it always Java guys who's playing with these benchmarks? Looks like an "inferiority syndrome" to me, C++ hackers just don't seem to care. Do you know why? Because good (performance-minded) C++ programmer has very good idea what kind of assembly instructions his code will turn to. This is why performance-critical code is still written in C++.

nickb3• 19 years ago

STL does have a few tarpits and once you know which classes to avid, it's smooth cruising. I recommend Scott Meyer's Effective C++ books if you want to learn how to avoid a lot of C++ performance black holes: http://www.aristeia.com/books_frames.html

Yes, the choice of a C++ compiler does make some difference in algo heavy functions/methods but the art of writing high performance C++ programs has a lot more to do with overall design (which is sometimes C++ specific) and your programming style. I left C++ programming but if that's your cup of tea, look into Meyer's books. They're the best.

Java guys care because of Java's history: it was always slower than compiled languages and Java dev got a lot of crap for not having fast runtime. That's all history but there's still a ton of people out there who refuse to download Java-based programs because of 'slowness' myth.

jey3• 19 years ago

No, C++ is not slower than C. Both C and C++ are effectively macro assembler languages, and if you know what the 'macro' expands to, you can gauge the performance. You could implement everything that's in C++ using just pure C and get the same effect, but I surely do not want to manually lay out my vtables nor do I want to replace my C++ templates with C preprocessor macros. :-)

It should also be no surprise that Java, with its runtime dynamic optimization, is able to more strongly optimize code based on runtime performance characteristics than compile time optimizations performed by traditional C and C++ compilers. This is just a guess, but it's also possible that the Java JIT compiler is able to more aggressively optimize the generated code by having more insight into pointer aliasing, whereas you'd need to do whole program compilation to get the same effect with C++. (Plug: LLVM can do whole program compilation. http://www.llvm.org )

As tx said in a sibling post: Because good (performance-minded) C++ programmer has very good idea what kind of assembly instructions his code will turn to. This is why performance-critical code is still written in C++.

nickb3• 19 years ago

Yes, C++ is unquestionably slower than C when you use it to the full potential and when you program the C++ way! A lot of people still program in C++ using the C style. I've used C++ for 7 yeas and have plenty of experience with it and I've seen its slowness in many instances. Main thing to avoid with C++ is virtual methods. Once you understand how they're implemented, you will understand why (hint: vtables).

ralph• 19 years ago

LLVM is outstanding, but little known. One example, a C program that uses a malloc-per-node linked list implementation might be compiled into an executable that uses an array, saving the space occupied by the pointers, and improving locality, because LLVM can analyse the whole program.

http://llvm.org/pubs/2005-06-12-MSP-PointerComp.html

http://llvm.org/pubs/2005-05-21-PLDI-PoolAlloc.html

nostrademons• 19 years ago

That's been my experience too, for heavy numeric computation. Hotspot can optimize the hell out of plain Java SE.

Something to keep in mind though: architectural considerations matter a whole lot more than the particular programming language you use to implement them. If you keep your programs simple and use tools like Java NIO when appropriate, you can write really fast code in Java. If you pile on framework after framework, of course it's going to be slow, because it's doing a whole lot more work.

It's very easy to write a screamingly-fast Java backend and then lose all your speed gains by sticking it behind Hibernate, JSF, and a half-dozen JavaScript libraries.

snorkel• 19 years ago

Interesting but Mandelbrot is a specific math process. I'd be more impressed if a large application with network I/O, disk I/O, threading, etc was proven to be faster in Java than in C.

henning• 19 years ago

With contrived benchmarks you can prove anything.

Pick something with weird bit twiddling where C is better. I pick some business computing task involving lots of systems integration or some shit where Java is better. And on and on.

Garbage collection is a megawin and you have to be retarded or working on microdevices with 168 bytes of RAM to use C over Java. And that's really where anything on the JVM wins.

Java faster than C

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