What is faster- Java or C# (or good old C)? [closed]

Answer 1

If there is already a significant quantity of legacy C code that will be added to the system then why move to C# and Java?

In response to your latest edit about wanting to take advantage of any improvements in processing speed....then your best bet would be to stick to C as it runs closer to the hardware than C# and Java which have the overhead of a runtime environment to deal with. The closer to the hardware you can get the faster you should be able to run. Higher Level languages such as C# and Java will result in quicker development times...but C...or better yet Assembly will result in quicker processing time...but longer development time.

Answer 2

If much of your code is in C why not keep it? In principal and by design it's obvious that C is faster. They may close the gap over time but they always have more level os indirection and "safety". C is fast because it's "unsafe". Just think about bound checking. Interfacing to C is supported in every langauge. And so I can not see why one would not like to just wrap the C code up if it's still working and use it in whatever language you like

Answer 3

If every percentage will really save you tens of thousands of dollars, then you should bring in a domain expert to help with the project. Well designed and written code with performance considered at the initial stages may be an order of magnitude faster, saving you 90%, or $900,000. I recently found a subtle flaw in some code that sped up a process by over 100 times. A colleague of mine found an algorithm that was running in O(n^3) that he re-wrote to make it O(N log n). This tends to be where the huge performance saving are.

If the problem is so simple that you are certain that a better algorithm cannot be employed giving you significant savings, then C is most likely your best language.

Answer 4

Writing in one language or another will only give you small speed ups for a large amount of work. To really speed things up you might want to look at the following:

1. Buying the latest fastest Hardware.
2. Moving from 32 bit operating system to 64 bit.
3. Grid computing.
4. CUDA / OpenCL.
5. Using compiler optimisation like vectorization.

Answer 5

My preference would be C or C++ because I'm not separated from the machine language by a JIT compiler.

You want to do intense performance tuning, and that means stepping through the hot spots one instruction at a time to see what it is doing, and then tweaking the source code so as to generate optimal assembler.

If you can't get the compiler to generate what you consider good enough assembler code, then by all means write your own assembler for the hot spot(s). You're describing a situation where the need for performance is paramount.

What I would NOT do if I were in your shoes (or ever) is rely on anecdotal generalizations about one language being faster or slower than another. What I WOULD do is multiple passes of intense performance tuning along the lines of THIS and THIS and THIS. I have done this sort of thing numerous times, and the key is to iterate the cycle of diagnosis-and-repair because every slug fixed makes the remaining ones more evident, until you literally can't squeeze another cycle out of that turnip.

Good luck.

Added: Is it the case that there is some seldom-changing configuration information that determines how the bulk of the data is processed? If so, it may be that the program is spending a lot of its time re-interpreting the configuration info to figure out what to do next. If so, it is usually a big win to write a code generator that will read the configuration info and generate an ad-hoc program that can whizz through the data without constantly having to figure out what to do.

Answer 6

Note that for heavy computations there is a great advantage in having tight loops which can fit in the CPU's first level cache as it avoids having to go to slower memory repeatedly to get the instructions.

Even for level two cache a large program like Quake IV gets a 10% performance increase with 4 Mb level 2 cache versus 1 Mb level 2 cache - http://www.tomshardware.com/reviews/cache-size-matter,1709-5.html

For these tight loops C is most likely the best as you have the most control of the generated machine code, but for everything else you should go for the platform with the best libraries for the particular task you need to do. For instance the netlib libraries are reputed to have very good performance for a very large set of problems, and many ports to other languages are available.