Daniël Mantione wrote:
Op Sun, 8 Oct 2006, schreef Vincent Snijders:
Daniël Mantione wrote:
Op Sat, 7 Oct 2006, schreef Florian Klaempfl:
Vincent Snijders schrieb:
I started to add vector pascal like support, currently only
i386/x86_64 are
supported (no generic support). The whole (currently implemented)
functionality is demonstrated by the following example. Please give
some
feedback if it allows benchmark speedups.
To get a large speedup, I think you should instead of making pairs of
doubles, do the pixels in parallel. I.e. in this benchmark, a row is 3000
pixels wide, so, make an array of 3000 doubles, and do the operation with
arrays. With proper compiler optimization, it should be possible to
achieve speeds close to 2 flops a clock cycle.
The 'problem' in this benchmark is that the number of iterations of the inner
loop isn't fixed, but can vary between 1 and 50. If you pair two doubles, the
change you can break the loop for all elements of the vector before iteration
50 is bigger than when you combine 3000 elements.
You are right. How about doing it in blocks of 8x8 pixels? The
high iteration loops are concentrated close to the borders of
the set, so for most blocks the iteration can then be ended early.
For starters I was thinking about blocks of 1x2 pixels ;-). The current
hardware doesn't allow any more parallelism anyway. Or am I making a
mistake in my thinking now?
Vincent
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