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spectre oceaneval function documentation

StevenMikes

The oceaneval capability in spectre seems to be very poorly documented. It is mentioned indirectly in a couple places in the manual, but that's all I can find.

I would like to know if it is possible to declare and make use of intermediate variables when constructing these expressions, like one can do in OCEAN. For example,

vclip = clip(vtime('tran "VOUT") 3n 4n)

vmax = ymax(vclip)

Is there a way to do something like this with oceaneval? Thanks in advance!

  • Andrew Beckett

    What are you using it for (I assume the export statement, but is this for Monte Carlo, or for normal spectre)? Which version are you using?

    The export statement is deprecated in spectre and the help has now been removed. Current flows do not use it, so I'm wondering why you're using it and what you're using it for?

    Regards,

    Andrew.

  • StevenMikes
    in reply to Andrew Beckett

    Andrew, I'm running Monte Carlo yes. The Spectre version is Version 16.1.0.567.isr12 64bit -- 12 Dec 2017 which is quite up-to-date.

    The manual for this version still includes references to oceaneval, mostly in the montecarlo statement section. It doesn't mention it being deprecated.

    I'm using it for the use shown in the manual, which is to save measurements to a .dat file when running montecarlo. 

    If this method is deprecated, what is the official replacement method?

    I should also mention that the reason for doing this is I believe it allows measurements to be printed out without having to save the nodes and process them in ocean afterwards.

  • Andrew Beckett
    in reply to StevenMikes

    If you use it, spectre does report:

    Warning from spectre during hierarchy flattening.
    WARNING (SPECTRE-18036): Support for export statement vdc will be deprecated in the next release.

    (this is in SPECTRE16.1 and SPECTRE17.1 - hasn't actually been removed yet).

    I believe that the supported command-line flow is to use SpectreMDL, or to save the waveforms and do the calculations after simulation. I'll ask R&D this when I contact them about the fact that the documentation still includes references to export and oceanEval.

    Regards,

    Andrew.

  • StevenMikes
    in reply to Andrew Beckett

    Hi Andrew, any word from R&D on this yet?


    I also have another reason for running this way: The Spectre montecarlo statement has a 'distributed' option that supports parallel processing to LSF pretty well. I don't think there is an equivalent in spectre MDL.

    Another point also: apparently spectre MDL montecarlo uses a different algorithm than the plain spectre montecarlo. The MDL version had a bug when used with our models that was giving erroneous results (we have an issue open on this already).  

  • Andrew Beckett
    in reply to StevenMikes

    I thought I'd replied to this already - but don't see it (perhaps I forgot to hit Reply). Anyway, I've not heard from R&D but have reiterated what you said about distributed (I'd given similar arguments in the past when discussing the proposed removal of the export statement support).

    If MDL is giving erroneous results, that's a bug. Not sure it's a different algorithm - it may just be a bug in that particular flow (I'm not aware of the specific issue you're referring to though).

    Regards,

    Andrew.

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