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Posted 2 Mar 2008


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C# vs C/C++ Performance

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1.54/5 (33 votes)
2 Mar 2008CC (ASA 2.5)5 min read
Comparison of Performance of C++ and C#


Well, this is my first post in this technology series. In fact, the title of this post, forced me to start of a technology focused blog. Well said about all these, let's now jump into the issue.

There has been a lot of heated discussion on different forums, newsgroups, and various other threads about the above topic. Now why should I discuss about the same again here?

Well, though there are many discussion groups that claim C++ to be faster and efficient, a small group of people still claim C# to be more efficient.
How the hell can a language that is not compiled to a native code be faster that a C++ binary?

Though the above statement is perfectly valid from the point of C++ programmers, I would like to highlight a few points that could state why some (not all) C# programs are *really faster* than it's equivalent C++ programs.

Point 1: C# is compiled twice. Once while the program is written and second when the program is executed at the user's site. The first compilation is done by your C# builder and the second by the .NET Framework on the user's machine. The reason why C# compiled applications could be faster is that, during the second compilation, the compiler knows the actual run-time environment and processor type and could generate instructions that targets a specific processor. Classical C++ compilers generate native code that is usually the Lowest Common Denominator of all the available processors which means, a C++ program will not be able to take the advantages of the "Hyper Threading" instruction set of the Pentium 4 HT processor. (Of course HT is outdated now...) It will also not be able to take advantages of the Core 2 duo or Core 2 Quad's "true multi-threaded" instruction set as the compiler generated native code does not even know about these instruction sets.
In the earlier days, not much changes were introduced to the instruction set with every processor release. The advancement in the processor was only in the speed and very few additional instruction sets with every release. Intel or AMD normally expects game developers to use these additional instruction sets. But with the advent of PIV and then on, with every release, PIV, PIV HT, Core, Core 2, Core 2 Quad, Extreme, and the latest Penryn, there are additional instruction sets that could be utilized if your application needs performance. There are C++ compilers that generate code that targets specific processors. But the disadvantage is the application has to be tagged as "This application's minimum system requirements are atleast a Core 2 Quad processor" which means a lot of customers will start to run away.
This is precisely where the C#'s framework compiler comes into picture. Because the application is compiled the second time at the user's site, the Framework knows about the actual running platform and is able to generate code that runs the best on the given platform.

Point 2: So, then why doesn't *all* C# programs run faster?

C# or for that matter any .NET based application runs in a sand-boxed environment and hence many instructions have to be checked for safety. Because additional safety is not free, C# comes with a performance overhead, which means a program like,

for(int i=0;i<100000000;i++)
// pig function

where Pig_Function() is a really time consuming operation, C++ is faster by a order of magnitude. Nearly all the threads I've seen that claims C++ is faster writes a small application like this a prove that C++ is atleast n times faster than an equivalent c++ program and yes it's true. Microsoft does not recommend using C# for time-critical applications.

Point 3: So when is C# really faster?
A well designed C# program is more than 90% as fast as an equivalent "well-designed" C++ program. But the catch is "well-designing" a C++ program. How many of us can manage memory efficiently in a C++ application that's so huge say a million lines of code? It's extremely difficult to "well-design" a C++ program especially when the program grows larger. The problem with "not-freeing" the memory at the right time is that the working set of the application increases which increases the number of "page faults". Everyone knows that page fault is one of the most time-consuming operation as it requires a hard disk access. One page fault and you are dead. Any optimization that you did spending your hours of time is wasted in this page fault because you did not "free" memory that you no longer needed. A lot of classical applications including Google Picasa suffers from memory management problems. After about two or three days, you can notice that these applications become slower necessitating a Windows Restart. This problem is completely alleviated in C#. the Framework comes with a broom behind you and sweeps your drop during the course of the execution and as a result your working set never grows (unless you really use it) which means lesser page faults. This means that "well-designing" a C++ program is far complicated than a equivalent C# program which is responsible for its sluggish performance.

So now I can hear you asking me,
So to conclude what should I do?
That's a nice question. Except for writing time-critical blocks of code, prefer C#. Write all your algorithmic code in C++ (not VC++ .NET), compile it into a dll and call that using a Dll Interop through C#. This should balance the performance. This technique is not new or not invented by me or anyone. It's similar the old age C programming vs Assembly, where people on one camp fight assembly programming is faster and the other camp stating C is easier to develop and then people started using assembly embedded within a C program for time-critical applications using an asm block.

History repeats...!


Originally Posted at my blog


Nothing much here.


This article, along with any associated source code and files, is licensed under The Creative Commons Attribution-ShareAlike 2.5 License


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Comments and Discussions

GeneralMy vote of 5 Pin
VHGN19-Apr-12 12:03
MemberVHGN19-Apr-12 12:03 
GeneralMy vote of 2 Pin
dmihailescu11-Apr-12 10:13
Memberdmihailescu11-Apr-12 10:13 
Question....One page fault and you are dead. Pin
Member 1700648-Oct-11 9:10
MemberMember 1700648-Oct-11 9:10 
GeneralMy vote of 1 Pin
Allen C. Copeland Jr.13-Oct-10 10:30
MemberAllen C. Copeland Jr.13-Oct-10 10:30 
General[My vote of 1] I don't think you know what you're talking about Pin
MatrixDud26-Mar-09 8:14
MemberMatrixDud26-Mar-09 8:14 
GeneralRe: [My vote of 1] I don't think you know what you're talking about Pin
Chaz Zeromus29-Sep-09 10:28
MemberChaz Zeromus29-Sep-09 10:28 
Generalbut I like C# more than C++ Pin
Xmen Real 26-Feb-09 16:28
professional Xmen Real 26-Feb-09 16:28 
GeneralRe: but I like C# more than C++ Pin
Mohammad Dayyan13-May-09 12:25
MemberMohammad Dayyan13-May-09 12:25 
GeneralRe: but I like C# more than C++ Pin
rjklindsay12-Apr-10 14:47
Memberrjklindsay12-Apr-10 14:47 
GeneralRe: but I like C# more than C++ Pin
ben.Kloosterman5-Jul-10 4:05
Memberben.Kloosterman5-Jul-10 4:05 
QuestionD is the solution? Pin
Herr Lucifer2-Jul-08 8:10
MemberHerr Lucifer2-Jul-08 8:10 
GeneralOther performance considerations Pin
Ralph Walden4-Mar-08 4:55
MemberRalph Walden4-Mar-08 4:55 
GeneralRe: Other performance considerations Pin
Blaisorblade15-Jan-09 18:14
MemberBlaisorblade15-Jan-09 18:14 
GeneralSo, the choice is.... Pin
Hernan Saez3-Mar-08 10:05
MemberHernan Saez3-Mar-08 10:05 
GeneralRe: So, the choice is.... Pin
User 15562333-Mar-08 16:05
MemberUser 15562333-Mar-08 16:05 
GeneralRe: So, the choice is.... Pin
leonej_dt31-Mar-11 5:40
Memberleonej_dt31-Mar-11 5:40 
QuestionWhy Memory management ? Pin
yassir hannoun2-Mar-08 7:52
Memberyassir hannoun2-Mar-08 7:52 
AnswerRe: Why Memory management ? Pin
Alexandre GRANVAUD2-Mar-08 21:52
MemberAlexandre GRANVAUD2-Mar-08 21:52 
GeneralRe: Why Memory management ? Pin
yassir hannoun3-Mar-08 2:35
Memberyassir hannoun3-Mar-08 2:35 
GeneralRe: Why Memory management ? Pin
Alexandre GRANVAUD3-Mar-08 3:00
MemberAlexandre GRANVAUD3-Mar-08 3:00 
AnswerRe: Why Memory management ? Pin
John M. Drescher3-Mar-08 9:09
MemberJohn M. Drescher3-Mar-08 9:09 
GeneralRe: Why Memory management ? Pin
Blaisorblade15-Jan-09 18:16
MemberBlaisorblade15-Jan-09 18:16 
Question??? Pin
HumanOsc2-Mar-08 7:09
MemberHumanOsc2-Mar-08 7:09 
GeneralNice Article But ... Pin
codeprojecter_2-Mar-08 4:28
Membercodeprojecter_2-Mar-08 4:28 
GeneralRe: Nice Article But ... Pin
User 15562332-Mar-08 5:19
MemberUser 15562332-Mar-08 5:19 

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