Back to General and Gameplay Programming

assembly is slower ?! (source included)

nosajghoul · 2004-03-25T11:56:30

Ok, newbie to assem, just probing the territory. I made 2 functions that do exactly the same thing. (Add a number together) but one uses assembly, the other not. (Im coding in MSVC++ 6.0 on a P3450 this evening, so your numbers will prolly b better ) I got the start time and finish time for each before I made it loop a million times (literally). I then output the total times, which should (shouldnt it?) be a benchmark of sorts for which is faster. I thought assembly would beat straight c, but nope. My results were : Assembly function = 1702, normal function = 1562. Normal was about .15 seconds faster. Why? And now for the code : #include <iostream.h> #include <windows.h> //for GetTickCount() int x = 0xFFFF; int y = 0xFFFF; int r = 0; void __fastcall AssemAdd() { _asm { mov eax, x mov ebx, y add eax, ebx mov r, eax } } void NormAdd() { r=x+y; } const int loops = 10000000; //10 million void main() { DWORD StartAssem = 0.0f; DWORD FinishAssem = 0.0f; DWORD TotalAssem = 0.0f; DWORD StartNorm = 0.0f; DWORD FinishNorm = 0.0f; DWORD TotalNorm = 0.0f; int x = 0; //log starttime StartAssem = GetTickCount(); for(x=0; x < loops; x++) AssemAdd(); //log finishtime FinishAssem = GetTickCount(); //calculate totaltime TotalAssem = FinishAssem - StartAssem; //now for not assembly //log starttime StartNorm = GetTickCount(); for(x=0; x < loops; x++) NormAdd(); //log finishtime FinishNorm = GetTickCount(); //calculate totaltime TotalNorm = FinishNorm - StartNorm; //output the times cout << endl << "Assem = " << TotalAssem; cout << endl << "Norm = " << TotalNorm; cout << endl; } Should work fine as is, in MSVC++ 6.0 at least. Its a console app, and when ran (on my comp anyway) it seems to hang for a second (its just doing 20 million things, thats all) and then outputs the time in milliseconds it took for the functions. Oh and could someone tell me what __fastcall is? Whats the technical term for those double underscored commands so I can look it up? -Jason

General and Gameplay Programming Programming

Started by nosajghoul March 21, 2004 05:12 PM

39 comments, last by nosajghoul 20 years ago

antareus

576

March 25, 2004 11:56 AM

quote:Original post by DevLiquidKnight
Depends on what deadlines, you have to meet, what if you were told your suppose to optimize something?

What if what you had to optimize was already ''optimized'' such that the original logic was obscured?

Everytime I see an assembly block in an application that doesn''t need it (e.g. Miranda''s event core) I roll my eyes and skip it. Meanwhile the comment proudly proclaims it only takes 10 cycles to hash the name of the event. Congrats, the code is unreadable because of optimization.

--God has paid us the intolerable compliment of loving us, in the deepest, most tragic, most inexorable sense.- C.S. Lewis

assembly is slower ?! (source included)

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

assembly is slower ?! (source included)

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Reticulating splines