Re: How to profile a VC++ program?
fastgo@gmail.com wrote:
Well, they are really simple getter methods. The two biggest hit
methods are
class A
{
public:
....
unsigned char getColor() const {return color;}
private:
unsigned char color;
};
class B
{
public:
.....
inline A * & getObject(unsigned int index) const
{
return objects[index];
}
private:
A ** objects;
};
These two methods under gcc only contribute 1% each by the gnu profile
tools. While under .NET 2003 VC++, each contributes 4%-5% with the
intel VTune analyzer.
Interesting. I'm suspicious that what you're seeing is some kind of
measurement artifact and not representative of the execution times of these
functions. These are returning built-in types and will definitely be
inlined, unless there's something important that you haven't shown - for
example, are these functions virtual? That's about the only reason I can
think of that the compiler wouldn't inline them.
The exact compiler command line is
/O2 /GL /I "C:\Documents and Settings\All
Users\Documents\Projects\include" /D "WIN32" /D "NDEBUG" /D "_CONSOLE"
/D "_MBCS" /FD /EHsc /ML /GS /Fo"Release/" /Fd"Release/vc70.pdb" /W3
/nologo /c /Wp64 /Zi /TP
That all looks fine. In your original post you indicated that your program
runs 2x slower under VC, but these functions, even if we accept the strange
numbers, only account for a few percent. Where is the rest of the time
difference?
One thing I notice - you're linking with the multi-threaded static CRT. Is
your gcc build linking with a multi-threaded runtime library? Usually that
doesn't make a large difference in overall program execution time, but there
certainly are pathological cases where using the MT version is quite a lot
slower.
Overall, how much execution time are we talking about here? - i.e. are you
talking about a second of execution time or a minute? If the former, it may
just be a difference in startup time. What's the overall texture of the
code - does it use STL? boost? Other libraries? Is it I/O heavy or CPU
bound? Does the code make extensive use of try/catch blocks?
Yes, I'm fishing for ideas - typically, VC produces faster code than gcc, so
there's got to be some reason for this particular code to be slower.
-cd