Re: [LAD] vectorization

On Wed, 2008-04-16 at 17:37 +0200, Remon wrote: Not a gcc developer, but 'man clock' says that clock is supposed to measure the time used by the application thus excluding the time spend by system and other applications, whereas gettimeofday is the wall clock including everything (as well as using a different unit of measurement.) To get the real clock-count for running one fragment - as opposed to the pseudo GHz return from 'clock' - you could use something like this: /* high resolution processor clock count */ static inline unsigned long long rdtsc() { unsigned long long int x; __asm__ volatile (".byte 0x0f, 0x31" : "=A" (x)); return x; } ... and then: long long clck= rdtsc(); for (int i = 0; i < RUNS; i++) { cpp_mix(pSampleInputBuf, pOutput, FRAGMENTSIZE, coeff); } printf ("pure C fragment\t\t: %d clck\n",(int)((rdtsc()-clck)/RUNS)); This could reveal something about how well you are utilizing the added execution units in later Intel hardware compared to a simple PIII celeron: Benchmarking mixdown (WITH coeff): pure C fragment : 1493 clck For your C2D, compile with -mssse3 rather than -sse --