[Beowulf] PCPro: AMD: what went wrong?

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Mon Feb 20 20:14:06 PST 2012



On 2/20/12 12:48 PM, "Vincent Diepeveen" <diep at xs4all.nl> wrote:

>
>On Feb 20, 2012, at 9:29 PM, Lux, Jim (337C) wrote:
>
>> Comments below about automated vs manual design..
>>
>> Granted modern place and route is very sophisticated, but
>> ultimately, it's
>> a heuristic process (Xilinx had simulated annealing back in the
>> 80s, for
>> instance) which is trying to capture routine guidelines and rules (as
>> opposed to trying guided random strategies like GA, etc.)
>
>Actually for hand optimization of yields at modern CPU's stuff like
>simulated annealing is less popular.

I don't know that anyone still uses simulated annealing..it was an example
of what kinds of strategies were used in the early days.  Back in the late
70s, early 80s, I was looking into automated layout of PCBs.  It was
pretty grim.. 80% routing, then it would die.   The computational
challenge is substantial.



>
>You can actually also use lineair solvers for that, in order to
>recalculate entire design and under the right
>constraints it gives an optimal solution, which is not garantueed for
>the non-lineair solving methods as
>those also easily can pick a local maximum.


I don't think a linear solver would work.
>
>Stuff like simulated annealing is more popular at the non-lineair
>problems such as in artificial intelligence.

The place and route problem is highly nonlinear with a lot of weird
interactions.

I'll be the first to confess that I am pretty bad at PCB or ASIC layout,
but there's a lot of tricky constraints that aren't a linear function of
position in some form.   Imagine having a data bus with 32 lines that you
need to have minimal skew between, so it can be latched.


I suppose this is a kind of game playing application so move tree search
strategies might work.  Certainly it has EP aspects (or nearly EP), so a
big parallel machine might help.  For all we know, Intel and AMD have big
clusters helping the designers out, running 1000 copies of timing
simulators.  Does Cadence, Synopsis, etc. have parallel versions?



>>



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