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Re: SMS scheduling


Canqun Yang <canqun@nudt.edu.cn> wrote on 28/09/2004 11:06:29:

> Hi, all
>
> I tested the Swing Modulo Scheduling of GCC. For
> simple program, the numerical caculation of PI, it
> achieves significant speedup on IA64. But, for little
> bit complex programs, the SMS can hardly work out a
> successful schedule.
>
> The algorithms implemented by Ayal and Mostafa are
> correct. It seems that the SMS itself is wrong. The
> schedule priority order calculated by SMS is much
> different from normal MinDist algorithm.

SMS prioritizes the nodes using critical patch based
heuristic - the main idea is that instructions that are
on the critical path are less flexible in means of
scheduling.
Why do you think that the priority order should be
according to MinDist algorithm (what is the minimum
distance in this case)? Can you provide an example
that supports this?

> Besides this,
> SMS is not sensitive to II. Is SMS really wrong?

The node ordering step in SMS is not sensitive to II
(as mentioned before it is based on critical path
heuristic).  However, the scheduling step is sensitive
to II - failing to schedule the nodes of a loop within
II cycles will lead to try scheduling the nodes again
within II + 1 cycles.


Mostafa.






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