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

Answer 1

Ref; "My benchmarks so far show Java and C are about on par with each other"

Then your benchmarks are severely flawed...

C will ALWAYS be orders of magnitudes faster then both C# and Java unless you do something seriously wrong...!

PS! Notice that this is not an attempt to try to bully neither C# nor Java, I like both Java and C#, and there are other reasons why you would for many problems choose either Java or C# instead of C. But neither Java nor C# would in a correct written tests NEVER be able to perform with the same speed as C...

Edited because of the sheer number of comments arguing against my rhetoric

Compare these two buggers...

C#

public class MyClass
{
   public int x;

   public static void Main()
   {
      MyClass[] y = new MyClass[1000000];
      for( int idx=0; idx < 1000000; idx++)
      {
          y[idx] = new MyClass();
          y[idx].x = idx;
      }
   }
}

against this one (C)

struct MyClass
{
   int x;
}

void Main()
{
   MyClass y[1000000];
   for( int idx = 0; idx < 1000000; idx++)
   {
      y[idx].x = idx;
   }
}

The C# version first of all needs to store its array on the heap. The C version stores the array on the stack. To store stuff on the stack is merely changing the value of an integer value while to store stuff on the heap means finding a big enough chunk of memory and potentially means traversing the memory for a pretty long time.

Now mostly C# and Java allocates huge chunks of memory which they keep on spending till it's out which makes this logic execute faster. But even then to compare this against changing the value of an integer is like an F16 against an oil tanker speedwise...

Second of all in the C version since all those objects are already on the stack we don't need to explicitly create new objects within the loop. Yet again for C# this is a "look for available memory operation" while the C version is a ZIP (do nothing operation)

Third of all is the fact that the C version will automatically delete all these objects when they run out of scope. Yet again this is an operation which ONLY CHANGES THE VALUE OF AN INTEGER VALUE. Which would on most CPU architectures take between 1 and 3 CPU cycles. The C# version doesn't do that, but when the Garbage Collector kicks in and needs to collect those items my guess is that we're talking about MILLIONS of CPU cycles...

Also the C version will instantly become x86 code (on an x86 CPU) while the C# version would first become IL code. Then later when executed it would have to be JIT compiled, which probably alone takes orders of magnitudes longer time then only executing the C version.

Now some wise guy could probably execute the above code and measure CPU cycles. However that's basically no point at all in doing because mathematically it's proven that the Managed Version would probably take several million times the number of CPU cycles as the C version. So my guess is that we're now talking about 5-8 orders of magnitudes slower in this example. And sure, this is a "rigged test" in that I "looked for something to prove my point", however I challenge those that commented badly against me on this post to create a sample which does NOT execute faster in C and which also doesn't use constructs which you normally never would use in C due to "better alternatives" existing.

Note that C# and Java are GREAT languages. I prefer them over C ANY TIME OF THE DAY. But NOT because they're FASTER. Because they are NOT. They are ALWAYS slower then C and C++. Unless you've coded blindfolded in C or C++...

Edit;

C# of course have the struct keyword, which would seriously change the speed for the above C# version, if we changed the C# class to a value type by using the keyword struct instead of class. The struct keyword means that C# would store new objects of the given type on the stack - which for the above sample would increase the speed seriously. Still the above sample happens to also feature an array of these objects.

Even though if we went through and optimized the C# version like this, we would still end up with something several orders of magnitudes slower then the C version...

A good written piece of C code will ALWAYS be faster then C#, Java, Python and whatever-managed-language-you-choose...

As I said, I love C# and most of the work I do today is C# and not C. However I don't use C# because it's faster then C. I use C# because I don't need the speed gain C gives me for most of my problems.

Both C# and Java is though ridiculously slower then C, and C++ for that matter...