Block/Loop Benchmarking

notes
Requires CPU with RDTSC support
code
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// Block-Process Benchmarking Code using rdtsc
// useful for measure DSP block stuff
// (based on Intel papers)
// 64-bit precission
// VeryUglyCode(tm) by Arguru

// globals
UINT time,time_low,time_high;

// call this just before enter your loop or whatever
void bpb_start()
{
    // read time stamp to EAX
    __asm rdtsc;
    __asm mov time_low,eax;
    __asm mov time_high,edx;
}

// call the following function just after your loop
// returns average cycles wasted per sample
UINT bpb_finish(UINT const num_samples)
{
    __asm rdtsc
    __asm sub eax,time_low;
    __asm sub edx,time_high;
    __asm div num_samples;
    __asm mov time,eax;
    return time;
}

Comments

If running windows on a mutliprocessor system, apparently it is worth calling:

SetThreadAffinityMask(GetCurrentThread(), 1);

to reduce artefacts.

(see http://msdn.microsoft.com/visualc/vctoolkit2003/default.aspx?pull=/library/en-us/dv_vstechart/html/optimization.asp)

__asm sub eax,time_low;
__asm sub edx,time_high;

should be

__asm sub eax,time_low
__asm SBB edx,time_high // substract with borrow