Am 14.07.20 um 20:54 schrieb Phil Hobbs:
> On 2020-07-14 12:14, Gerhard Hoffmann wrote:
>> Am 14.07.20 um 17:50 schrieb bitrex:
>>
>>>> I suggested to Mike E that LT Spice should use a graphic card for
>>>> computation, but I guess that's not going to happen now.
>>>>
>>>> A modest Windows PC can spin Solidworks 3D images around just fine.
>>>>
>>>>
>>>>
>>>
>>> Is SPICE trivially parallelize-able in that way?
>>
>> No. Inverting the conductivity matrix is hard because you
>> cannot do the pivoting in advance. The necessity shows
>> up during work.
>>
>> For transient analysis, every time step builds on the previous one(s)
>> and you cannot parallelize a lot of them because you don't know
>> the starting condition of the future ones.
>>
>> It has been tried often, a working solution would have been worth gold.
>> I remember the Weitek array coprocessor back in 80386 times and
>> a try with the NS16032. They never got a factor of more than 2 or 3.
>>
>> Everything really interesting is np-complete. :-(
>>
>> Cheers, Gerhard
>>
>
> It probably could be, if you changed the scheme so as to impose a
> speed-of-light propagation limit. That way you could divide the
> schematic up into chunks, do time steps locally, and then propagate the
> changes to adjacent chunks.
This was my proposal at Z80 / AM9511/AM9512 times, just one node
per square mm of DUT chip. I also tried to port Spice 2G6
to Interactive Unix on my 80286/287 Bullet board. What a fiasco.
64K segments conspiring with f2c as a Fortran compiler. Never could
have worked.
But this computer had 2 MB and a 70 MB Fujitsu disk. That was pure
hubris in the hands of a EE & CS student. Our VAX11 at the semiconductor
institute had 2 300 MB Fujitsu Eagles for all people together. :-)
And we made real chip designs on it.
Later I had a T800 transputer cluster, that would have mapped nicely
to this problem. But I never could find a customer for any T800
solution I proposed. All went X86.
The only exception was smuggling a Parsytec cluster to east Berlin.
But little Gerhard did not dare to. Few did I know. Some weeks
later, all the sudden, was the German re-unification and nobody would
have cared anymore about smuggling technology to an east-German
railway company that went belly-up anyway. Sigh.
> That gets rid of every node having to know about every other node on
> every time step, and makes FDTD codes such as my POEMS facility
> parallelize well. (It works that way.)
>
> Linear algebra also can be made to vectorize well on the right hardware.
>
> Cheers
Gerhard