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performance puzzle

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questionc++performancecsharpcss
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  • L Lost User

    Are you sure you got the optimized version of the C# code? I mean, yea it's supposed to be lame, but it's worse than I expected

    S Offline
    S Offline
    Super Lloyd
    wrote on last edited by
    #46

    Yes it! :( Is it that bad? I'm not that conversant in ASM, so I couldn't tell... But in a way that's good news, they have room for improvement! Now, what are they waiting for!?! :rolleyes:

    A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

    1 Reply Last reply
    0
    • D Daniel Grunwald

      Yes but where did you get the disassembled C# code from? It looks like all locals are on the stack (never in registers), which the JIT normally does only when a debugger is attached.

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      Super Lloyd
      wrote on last edited by
      #47

      Ha, the disassembly I got it from VS! Not sure how to get it otherwise... Because on the disk it's not compiled, it's just MSIL, and even if I NGen I dunno where they store the compiled version! (BTW I just tried NGen and it was not faster!?!)

      A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

      D 1 Reply Last reply
      0
      • M Mechanical

        Aamir Butt wrote:

        In some cases, C# can outperform C/C++

        How about ALL cases ? People who talk about C# (or any other retards' language) performance are talking about void while engaged with other C# (or any other retards' language) performance addicts in group masturbation. The link in your post points to another post by a C# guru (read as: VB guru). It says: "Remember : Engineers are expensive and servers are not!". Look at that! I mean just look at how pathetic that retard is.

        Aamir Butt wrote:

        However, if you like to follow the sheep, go ahead.

        I'll bet you are one of those that believe Java is the future of 3D.

        NULL

        A Offline
        A Offline
        Aamir Butt
        wrote on last edited by
        #48

        Mechanical wrote:

        I'll bet you are one of those that believe Java is the future of 3D.

        Java... Hahahaha... well I can't stop laughing. I haven't worked in Java since school. And I bet you are the one who writes all his linked list, hashtable, search and sorting algorithm from scratch because he believes that he can do better than those retards.

        Mechanical wrote:

        How about ALL cases ?

        Well, give me a case you are talking about but before that, give me the name of a NON-RETARD language as per your understanding.

        1 Reply Last reply
        0
        • D DaveAuld

          Nothing to do with the optimisation, but what about using the StopWatch class instead of datetime? Start the stop watch immediately before you enter the loop, and then stop it as soon as the loop exists.

          Dave Find Me On: Web|Facebook|Twitter|LinkedIn CPRepWatcher now available as Packaged Chrome Extension, visit my articles for link.

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          Super Lloyd
          wrote on last edited by
          #49

          well, I run 10000 thousand iteration to compare them, so DateTime seems precise enough! :) I did use StopWatch in the past but, I dunno, was never converted to it, I guess I never needed to make measurement precise enough!

          A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

          1 Reply Last reply
          0
          • S Super Lloyd

            Ha, the disassembly I got it from VS! Not sure how to get it otherwise... Because on the disk it's not compiled, it's just MSIL, and even if I NGen I dunno where they store the compiled version! (BTW I just tried NGen and it was not faster!?!)

            A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

            D Offline
            D Offline
            Daniel Grunwald
            wrote on last edited by
            #50

            Super Lloyd wrote:

            Ha, the disassembly I got it from VS! Not sure how to get it otherwise...

            To get the optimized JITted assembly code, you need to run your program from the command line, then attach the debugger to the running process, and click Break. Because your Main function was already running before you attached the debugger, it will still have the real native code. .NET doesn't re-jit anything when attaching a debugger.

            S 1 Reply Last reply
            0
            • D Dan Neely

              Aamir Butt wrote:

              See here for a performance comparison between different languages[^]

              The comments on that post were staggeringly stupid. :((

              3x12=36 2x12=24 1x12=12 0x12=18

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              A Offline
              Aamir Butt
              wrote on last edited by
              #51

              Dan Neely wrote:

              The comments on that post were staggeringly stupid.

              Yes, unfortunately. There are other performance comparisons as well but there is no point in posting the links here. As i said earlier, following the sheep..... :)

              1 Reply Last reply
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              • S Simon P Stevens

                Well I've written a C# version that runs 15-20% faster that your original on my PC. It doesn't use unsafe either. But I don't think you'll like it.

                private static void SafeTest_Improved1(string[] args)
                {
                int NUM = int.Parse(args[0]);
                int end = 8193;
                var primes = new byte[8193]{
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,

                    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
                
                S Offline
                S Offline
                Super Lloyd
                wrote on last edited by
                #52

                :laugh: you could have moved the "for(...) prims[i] = 1" statement out of the loop for the same (and more condensed) result! But this is an unfair comparison with C++, you removed a whole set a "required" operation for the algorithm! Although... I wonder if an array copy from an initialized array would speed up things....

                A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

                1 Reply Last reply
                0
                • D Derek Viljoen

                  Mechanical, I checked your profile. You've never authored an article, posted a snippet, entered a blog post, or otherwise shared any original thought, except to snipe at other people's comments on the message boards. In other words, you have yet to provide any empirical evidence for your worth to this site. No be a good boy and go away, please.

                  M Offline
                  M Offline
                  Mechanical
                  wrote on last edited by
                  #53

                  Derek Viljoen wrote:

                  In other words, you have yet to provide any empirical evidence for your worth to this site. No be a good boy and go away, please.

                  You have much to learn, little one.

                  NULL

                  R 1 Reply Last reply
                  0
                  • L Lost User

                    Post it?

                    S Offline
                    S Offline
                    Super Lloyd
                    wrote on last edited by
                    #54

                    okay, I ran it from the command line and attached a debugger, here is the release version, run and optimized at its best I guess. what do you think? (well, if you can read that! :~ ) (no inline C# comment this time!) ===============================================

                    00000000 push ebp
                    00000001 mov ebp,esp
                    00000003 push edi
                    00000004 push esi
                    00000005 push ebx
                    00000006 sub esp,48h
                    00000009 mov esi,ecx
                    0000000b lea edi,[ebp-54h]
                    0000000e mov ecx,12h
                    00000013 xor eax,eax
                    00000015 rep stos dword ptr es:[edi]
                    00000017 mov ecx,esi
                    00000019 mov dword ptr [ebp-10h],esp
                    0000001c mov dword ptr [ebp-54h],496CC9B0h
                    00000023 cmp dword ptr [ecx+4],1
                    00000027 je 00000043
                    00000029 call 620CD310
                    0000002e mov ecx,eax
                    00000030 mov edx,dword ptr ds:[03522030h]
                    00000036 mov eax,dword ptr [ecx]
                    00000038 call dword ptr [eax+000000D8h]
                    0000003e jmp 0000017B
                    00000043 cmp dword ptr [ecx+4],0
                    00000047 jbe 00000191
                    0000004d mov esi,dword ptr [ecx+0Ch]
                    00000050 call 620C0CC0
                    00000055 push eax
                    00000056 mov ecx,esi
                    00000058 mov edx,7
                    0000005d call 620CF2F0
                    00000062 mov ebx,eax
                    00000064 lea edi,[ebp-30h]
                    00000067 xor eax,eax
                    00000069 stos dword ptr es:[edi]
                    0000006a stos dword ptr es:[edi]
                    0000006b lea ecx,[ebp-30h]
                    0000006e call 62069650
                    00000073 call 62069730
                    00000078 mov ecx,eax
                    0000007a lea eax,[ebp-30h]
                    0000007d push dword ptr [eax+4]
                    00000080 push dword ptr [eax]
                    00000082 lea edx,[ebp-18h]
                    00000085 mov eax,dword ptr [ecx]
                    00000087 call dword ptr [eax+48h]
                    0000008a mov ecx,801h
                    0000008f push 0
                    00000091 dec ecx
                    00000092 jne 0000008F
                    00000094 mov ecx,esp
                    00000096 mov dword ptr [ebp-10h],esp
                    00000099 mov esi,ecx
                    0000009b jmp 000000DA
                    0000009d xor edx,edx
                    0000009f mov byte ptr [esi+edx],1
                    000000a3 inc edx
                    000000a4 cmp edx,2001h
                    000000aa jl 0000009F
                    000000ac mov ecx,2
                    000000b1 cmp byte ptr [esi+ecx],0
                    000000b5 je 000000D1
                    000000b7 mov edx,ecx
                    000000b9 add edx,edx
                    0000

                    L D 2 Replies Last reply
                    0
                    • D Daniel Grunwald

                      Super Lloyd wrote:

                      Ha, the disassembly I got it from VS! Not sure how to get it otherwise...

                      To get the optimized JITted assembly code, you need to run your program from the command line, then attach the debugger to the running process, and click Break. Because your Main function was already running before you attached the debugger, it will still have the real native code. .NET doesn't re-jit anything when attaching a debugger.

                      S Offline
                      S Offline
                      Super Lloyd
                      wrote on last edited by
                      #55

                      Thanks, done! Posted there: http://www.codeproject.com/Lounge.aspx?msg=3657593#xx3657593xx[^] However, I'm not conversant in ASM, so I can't tell much from it...

                      A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

                      1 Reply Last reply
                      0
                      • S Super Lloyd

                        okay, I ran it from the command line and attached a debugger, here is the release version, run and optimized at its best I guess. what do you think? (well, if you can read that! :~ ) (no inline C# comment this time!) ===============================================

                        00000000 push ebp
                        00000001 mov ebp,esp
                        00000003 push edi
                        00000004 push esi
                        00000005 push ebx
                        00000006 sub esp,48h
                        00000009 mov esi,ecx
                        0000000b lea edi,[ebp-54h]
                        0000000e mov ecx,12h
                        00000013 xor eax,eax
                        00000015 rep stos dword ptr es:[edi]
                        00000017 mov ecx,esi
                        00000019 mov dword ptr [ebp-10h],esp
                        0000001c mov dword ptr [ebp-54h],496CC9B0h
                        00000023 cmp dword ptr [ecx+4],1
                        00000027 je 00000043
                        00000029 call 620CD310
                        0000002e mov ecx,eax
                        00000030 mov edx,dword ptr ds:[03522030h]
                        00000036 mov eax,dword ptr [ecx]
                        00000038 call dword ptr [eax+000000D8h]
                        0000003e jmp 0000017B
                        00000043 cmp dword ptr [ecx+4],0
                        00000047 jbe 00000191
                        0000004d mov esi,dword ptr [ecx+0Ch]
                        00000050 call 620C0CC0
                        00000055 push eax
                        00000056 mov ecx,esi
                        00000058 mov edx,7
                        0000005d call 620CF2F0
                        00000062 mov ebx,eax
                        00000064 lea edi,[ebp-30h]
                        00000067 xor eax,eax
                        00000069 stos dword ptr es:[edi]
                        0000006a stos dword ptr es:[edi]
                        0000006b lea ecx,[ebp-30h]
                        0000006e call 62069650
                        00000073 call 62069730
                        00000078 mov ecx,eax
                        0000007a lea eax,[ebp-30h]
                        0000007d push dword ptr [eax+4]
                        00000080 push dword ptr [eax]
                        00000082 lea edx,[ebp-18h]
                        00000085 mov eax,dword ptr [ecx]
                        00000087 call dword ptr [eax+48h]
                        0000008a mov ecx,801h
                        0000008f push 0
                        00000091 dec ecx
                        00000092 jne 0000008F
                        00000094 mov ecx,esp
                        00000096 mov dword ptr [ebp-10h],esp
                        00000099 mov esi,ecx
                        0000009b jmp 000000DA
                        0000009d xor edx,edx
                        0000009f mov byte ptr [esi+edx],1
                        000000a3 inc edx
                        000000a4 cmp edx,2001h
                        000000aa jl 0000009F
                        000000ac mov ecx,2
                        000000b1 cmp byte ptr [esi+ecx],0
                        000000b5 je 000000D1
                        000000b7 mov edx,ecx
                        000000b9 add edx,edx
                        0000

                        L Offline
                        L Offline
                        Lost User
                        wrote on last edited by
                        #56

                        Is it a Debug build?

                        S 1 Reply Last reply
                        0
                        • S Super Lloyd

                          okay, I ran it from the command line and attached a debugger, here is the release version, run and optimized at its best I guess. what do you think? (well, if you can read that! :~ ) (no inline C# comment this time!) ===============================================

                          00000000 push ebp
                          00000001 mov ebp,esp
                          00000003 push edi
                          00000004 push esi
                          00000005 push ebx
                          00000006 sub esp,48h
                          00000009 mov esi,ecx
                          0000000b lea edi,[ebp-54h]
                          0000000e mov ecx,12h
                          00000013 xor eax,eax
                          00000015 rep stos dword ptr es:[edi]
                          00000017 mov ecx,esi
                          00000019 mov dword ptr [ebp-10h],esp
                          0000001c mov dword ptr [ebp-54h],496CC9B0h
                          00000023 cmp dword ptr [ecx+4],1
                          00000027 je 00000043
                          00000029 call 620CD310
                          0000002e mov ecx,eax
                          00000030 mov edx,dword ptr ds:[03522030h]
                          00000036 mov eax,dword ptr [ecx]
                          00000038 call dword ptr [eax+000000D8h]
                          0000003e jmp 0000017B
                          00000043 cmp dword ptr [ecx+4],0
                          00000047 jbe 00000191
                          0000004d mov esi,dword ptr [ecx+0Ch]
                          00000050 call 620C0CC0
                          00000055 push eax
                          00000056 mov ecx,esi
                          00000058 mov edx,7
                          0000005d call 620CF2F0
                          00000062 mov ebx,eax
                          00000064 lea edi,[ebp-30h]
                          00000067 xor eax,eax
                          00000069 stos dword ptr es:[edi]
                          0000006a stos dword ptr es:[edi]
                          0000006b lea ecx,[ebp-30h]
                          0000006e call 62069650
                          00000073 call 62069730
                          00000078 mov ecx,eax
                          0000007a lea eax,[ebp-30h]
                          0000007d push dword ptr [eax+4]
                          00000080 push dword ptr [eax]
                          00000082 lea edx,[ebp-18h]
                          00000085 mov eax,dword ptr [ecx]
                          00000087 call dword ptr [eax+48h]
                          0000008a mov ecx,801h
                          0000008f push 0
                          00000091 dec ecx
                          00000092 jne 0000008F
                          00000094 mov ecx,esp
                          00000096 mov dword ptr [ebp-10h],esp
                          00000099 mov esi,ecx
                          0000009b jmp 000000DA
                          0000009d xor edx,edx
                          0000009f mov byte ptr [esi+edx],1
                          000000a3 inc edx
                          000000a4 cmp edx,2001h
                          000000aa jl 0000009F
                          000000ac mov ecx,2
                          000000b1 cmp byte ptr [esi+ecx],0
                          000000b5 je 000000D1
                          000000b7 mov edx,ecx
                          000000b9 add edx,edx
                          0000

                          D Offline
                          D Offline
                          Daniel Grunwald
                          wrote on last edited by
                          #57

                          That looks quite similar to the C++ assembler code! Here, compare the main loop bodies. I've added annotations to the C# assembler code. C#:

                          000000b1 cmp byte ptr [esi+ecx],0 // primes[i] != 0
                          000000b5 je 000000D1
                          // if (primes[i] != 0) {
                          000000b7 mov edx,ecx
                          000000b9 add edx,edx // int k = 2 * i
                          000000bb cmp edx,2001h // k < end
                          000000c1 jge 000000D1
                          // for {
                          000000c3 mov byte ptr [esi+edx],0 // primes[k] = 0;
                          000000c7 add edx,ecx // k += i
                          000000c9 cmp edx,2001h // k < end
                          000000cf jl 000000C3
                          // }
                          // }
                          000000d1 inc ecx // ++i
                          000000d2 cmp ecx,2001h // i < end
                          000000d8 jl 000000B1

                          C++:

                                              if (primes\[i\] != 0)
                          

                          002610A0 cmp byte ptr [esp+ecx+10h],bl
                          002610A4 je wmain+0BDh (2610BDh)
                          {
                          int p = i; // using this extra variable speeds up C++!!! (and slow down C# if I do it)
                          for (int k = i + p; k < end; k += p)
                          002610A6 lea eax,[ecx+ecx]
                          002610A9 cmp eax,2001h
                          002610AE jge wmain+0BDh (2610BDh)
                          primes[k] = 0;
                          002610B0 mov byte ptr [esp+eax+10h],bl
                          002610B4 add eax,ecx
                          002610B6 cmp eax,2001h
                          002610BB jl wmain+0B0h (2610B0h)

                          	for (int i = begin; i < end; ++i)
                          

                          002610BD inc ecx
                          002610BE cmp ecx,2001h
                          002610C4 jl wmain+0A0h (2610A0h)

                          The C++ compiler was a bit more clever in combining mov+add into lea, but other than that, the instructions are identical. C++ also lifted the 0 literal into a register (bl), but I'm not sure if that gives you a performance advantage over immediates. (this optimization does give you a code size advantage though, at least for data types larger than 1 byte) So I'm not sure if this small optimization (lea) is causing the difference in performance, or if the reason for the difference is outside this loop. Because there's a major difference in the 'reset to 1' loop: C# resets each byte individually, whereas C++ calls the much faster memset. You could try rewriting that C# loop to:

                                      int\* primesInt = (int\*)primes;
                          	for (int i = 0; i < ((end-1)/sizeof(int))+1; i++)
                          		primesInt\[i\] = 0x01010101;
                          

                          Maybe even try if long is faster on your machine. In fact, I have the suspicion that the C++ memset might use SSE registers to set 16 ele

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                          • S Super Lloyd

                            Well it's only tip #237, so I guess it's not the 1st thing I should rush to do! :)

                            A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

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                            D Offline
                            Dan Neely
                            wrote on last edited by
                            #58

                            Super Lloyd wrote:

                            Well it's only tip #237, so I guess it's not the 1st thing I should rush to do! Smile

                            Yeah, but not for that reason. John's higher tips aren't in sequential order. A lot of the high priority ones are probably within this set: 9, 22, 32, 38, 44, 45, 50, 306, 308, 357, 454, 556, 762. :cool:

                            3x12=36 2x12=24 1x12=12 0x12=18

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                            • M Mechanical

                              Derek Viljoen wrote:

                              In other words, you have yet to provide any empirical evidence for your worth to this site. No be a good boy and go away, please.

                              You have much to learn, little one.

                              NULL

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                              Richard A Dalton
                              wrote on last edited by
                              #59

                              Mechanical wrote:

                              You have much to learn, little one.

                              Ain't it grand....that whole internet anonymity thang?!? Helping people work out their inner troll issues. Go read 'Richter' and stop bothering the grown ups. -Richard

                              Hit any user to continue.

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                              • D Daniel Grunwald

                                That looks quite similar to the C++ assembler code! Here, compare the main loop bodies. I've added annotations to the C# assembler code. C#:

                                000000b1 cmp byte ptr [esi+ecx],0 // primes[i] != 0
                                000000b5 je 000000D1
                                // if (primes[i] != 0) {
                                000000b7 mov edx,ecx
                                000000b9 add edx,edx // int k = 2 * i
                                000000bb cmp edx,2001h // k < end
                                000000c1 jge 000000D1
                                // for {
                                000000c3 mov byte ptr [esi+edx],0 // primes[k] = 0;
                                000000c7 add edx,ecx // k += i
                                000000c9 cmp edx,2001h // k < end
                                000000cf jl 000000C3
                                // }
                                // }
                                000000d1 inc ecx // ++i
                                000000d2 cmp ecx,2001h // i < end
                                000000d8 jl 000000B1

                                C++:

                                                    if (primes\[i\] != 0)
                                

                                002610A0 cmp byte ptr [esp+ecx+10h],bl
                                002610A4 je wmain+0BDh (2610BDh)
                                {
                                int p = i; // using this extra variable speeds up C++!!! (and slow down C# if I do it)
                                for (int k = i + p; k < end; k += p)
                                002610A6 lea eax,[ecx+ecx]
                                002610A9 cmp eax,2001h
                                002610AE jge wmain+0BDh (2610BDh)
                                primes[k] = 0;
                                002610B0 mov byte ptr [esp+eax+10h],bl
                                002610B4 add eax,ecx
                                002610B6 cmp eax,2001h
                                002610BB jl wmain+0B0h (2610B0h)

                                	for (int i = begin; i < end; ++i)
                                

                                002610BD inc ecx
                                002610BE cmp ecx,2001h
                                002610C4 jl wmain+0A0h (2610A0h)

                                The C++ compiler was a bit more clever in combining mov+add into lea, but other than that, the instructions are identical. C++ also lifted the 0 literal into a register (bl), but I'm not sure if that gives you a performance advantage over immediates. (this optimization does give you a code size advantage though, at least for data types larger than 1 byte) So I'm not sure if this small optimization (lea) is causing the difference in performance, or if the reason for the difference is outside this loop. Because there's a major difference in the 'reset to 1' loop: C# resets each byte individually, whereas C++ calls the much faster memset. You could try rewriting that C# loop to:

                                            int\* primesInt = (int\*)primes;
                                	for (int i = 0; i < ((end-1)/sizeof(int))+1; i++)
                                		primesInt\[i\] = 0x01010101;
                                

                                Maybe even try if long is faster on your machine. In fact, I have the suspicion that the C++ memset might use SSE registers to set 16 ele

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                                Super Lloyd
                                wrote on last edited by
                                #60

                                Thanks Daniel, this is all very enligthening comments! :-D Further I tried your suggestion and changed the setting to 1 as follow (remember prime is a stackalloc in C# so it's already a pointer)

                                var lprim = (long*)primes;
                                for (int i = 0; i < (end / 8); i++)
                                lprim[i] = 0x0101010101010101L;

                                and the speed is now very close to C++ (5% slower) overall it's quite good for C# after reflection hey! :)

                                A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

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                                0
                                • D Dan Neely

                                  Super Lloyd wrote:

                                  Well it's only tip #237, so I guess it's not the 1st thing I should rush to do! Smile

                                  Yeah, but not for that reason. John's higher tips aren't in sequential order. A lot of the high priority ones are probably within this set: 9, 22, 32, 38, 44, 45, 50, 306, 308, 357, 454, 556, 762. :cool:

                                  3x12=36 2x12=24 1x12=12 0x12=18

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                                  Super Lloyd
                                  wrote on last edited by
                                  #61

                                  It's all clear now! :-D

                                  A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

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                                  • L Lost User

                                    Is it a Debug build?

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                                    Super Lloyd
                                    wrote on last edited by
                                    #62

                                    Hey, it's not so bad! Look at the latest comment from Daniel from the assembly code which has been found by attaching to a running process: http://www.codeproject.com/Lounge.aspx?msg=3657636#xx3657636xx[^] Further I managed to get quite close to C++ (5% slower) by changing the loop which sets the bytes to 1, by writing something close to what the C++ compiler did, thanks to Daniel's comment!

                                    A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

                                    L 1 Reply Last reply
                                    0
                                    • S Super Lloyd

                                      Hey, it's not so bad! Look at the latest comment from Daniel from the assembly code which has been found by attaching to a running process: http://www.codeproject.com/Lounge.aspx?msg=3657636#xx3657636xx[^] Further I managed to get quite close to C++ (5% slower) by changing the loop which sets the bytes to 1, by writing something close to what the C++ compiler did, thanks to Daniel's comment!

                                      A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

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                                      L Offline
                                      Lost User
                                      wrote on last edited by
                                      #63

                                      It's not too bad, but it has an int3 in it

                                      S 1 Reply Last reply
                                      0
                                      • L Lost User

                                        It's not too bad, but it has an int3 in it

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                                        Super Lloyd
                                        wrote on last edited by
                                        #64

                                        int3!?! I don't speak assembly :sigh: , please explain! ;)

                                        A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

                                        L 1 Reply Last reply
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                                        • S Super Lloyd

                                          int3!?! I don't speak assembly :sigh: , please explain! ;)

                                          A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

                                          L Offline
                                          L Offline
                                          Lost User
                                          wrote on last edited by
                                          #65

                                          int3 is "debug break", on windows, if there is no debugger attached it causes the program to be halted and you will get a dialog asking you whether you want to debug the program.

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