[Ffmpeg-devel] int vs. float profiler, take 2
Mike Melanson
mike
Sat May 21 01:05:30 CEST 2005
Hi,
Since the first version of my little profiler generated a reasonable
amount of activity, attached is a slightly improved version. This one
does the following:
* runs all 4 of the functions n times as a cache warmup (n=1000 in the
code); this actually does help with cycle count consistency
* fetches an overhead cycle count as a baseline
* C code can fetch iteration count
The ASM code has ITERATIONS set to 1 right now. I would be interested to
know the results from varying CPUs using 1, 10, and 100 iterations.
Results from my VIA P3-class CPU:
warming up with 1000 cycles...
integer_adder(), 1 adds, 27 cycles used (overhead = 26)
float_adder(), 1 adds, 27 cycles used (overhead = 26)
integer_mult(), 1 mults, 34 cycles used (overhead = 28)
float_mult(), 1 mults, 27 cycles used (overhead = 26)
warming up with 1000 cycles...
integer_adder(), 10 adds, 36 cycles used (overhead = 26)
float_adder(), 10 adds, 36 cycles used (overhead = 26)
integer_mult(), 10 mults, 115 cycles used (overhead = 28)
float_mult(), 10 mults, 36 cycles used (overhead = 26)
warming up with 1000 cycles...
integer_adder(), 100 adds, 156 cycles used (overhead = 26)
float_adder(), 100 adds, 576 cycles used (overhead = 26)
integer_mult(), 100 mults, 925 cycles used (overhead = 28)
float_mult(), 100 mults, 578 cycles used (overhead = 26)
The benchmark still suffers from the result dependency problem. But the
same problem comes up in the multimedia decoding algorithms, right? If
the multiplications were parallelizable, wouldn't we be using
SSE/SSE2/AltiVec instructions to parallelize them?
Thanks...
--
-Mike Melanson
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