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assert warning indicating discontinuation of MDL assert evaluator

Zol

Hi everybody,

I have defined an assert checking the voltage on a given node as shown below:

sla1 assert expr="V(DUT.node\<1\>)" min=-0.25 max=0.25 check_windows=[80u 9999] level=error anal_types=[tran]

Spectre gave me the following warning:

WARNING (SPECTRE-17003): Assert `sla1' contains an expression that needs to be evaluated by MDL. Using this assert frequently may lead to performance issues because the MDL evaluator is slower than the native assert evaluator. Support for evaluating assert expressions using MDL will be discontinued in future releases.

I was not able to find anything about the native assert evaluator in the Spectre User Guide or in the Spectre Reference. Could somebody give me a few keywords and the name of the doc, where it is described? I would future proof the assert implementation and I would be happy if the simulation time would not increase for a voltage range check.

I use Spectre Version 20.1.0.348.isr10.

Best,
Zoltan

  • Zoltan,

    I don't see that message when I use your assert in an example I just tried (with the same version of Spectre). The idea is that we are gradually replacing the evaluation of various expressions in MDL with a native handler that doesn't require MDL to be used, and this is faster. There's no change of syntax as we do this - it's just a note to indicate that slower assertions may be in use (particularly helpful when we're looking at performance issues).

    In this case because it's a simple V() check, I think it should also work (from my tests too) if you change to:

    sla1 assert param=V(DUT.node\<1\>) min=-0.25 max=0.25 check_windows=[80u 9999] level=error anal_types=[tran]

    Regards,

    Andrew

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