I am using 6.1.5 environment and I have ran a monte-carlo simulation over 100 runs yesterday and I load back my results. Some runs have failed and I wish to see more data on these particulars seeds. I went to the monte-carlo options and choose the specific seed number and re-run only this one with monte-carlo.
As a result, I do not have the correct seed environment and so the same results.
How could I re-run a specific seed number from a monte-carlo run with all data such dc voltage, dc operating point, waveforms specified, ...?
Thanks in advance for your help,
The best way is not to mess around with the "seed". If the seed was not set, it defaults to 12345. It's the start run number that you'd want to use, rather than the seed. The seed alters the sequence of random numbers that are generated, and the start run number tells you how far that sequence you are.
The easiest way is take your full 100 run monte carlo results, switch to Detailed view (rather than Yield), and then over the particular run numbers that failed, do a right-mouse-button->Create Statistical Corner. This will then add into the corners the specific runs which you're interested in.
Then if you run in Single Run, Sweeps and Corners mode, and have the corners enabled, it will re-run the specific monte carlo points that you're interested in - making it easier to debug them.
Thanks for your quick reply.
I select the run number of interest and create a statistical run after reloaded the monte-carlo run from yesterday (reload results). Then run only this new run as a Single Run, ...
The outcome results are not the same as the specific one selected. How could I make sure this new run created is the one which failed in the monte-carlo run?
They should be the same. If they're not, you should log a service request with us to take a look. Potentially there are some situations where the circuit has multiple operating points and it might converge due to subtle differences in starting conditions to one or the other - but it's hard to tell without seeing the data.
I use statistical corners and I can re-produce the same montecarlo run number result when re-run as single statistical corner run on the same cct. What concerns me however is har far can you change your cct before that worst case statistical corner is no longer valid? I understand your flow suggests using statitstical corners to parametric optimize a cct but is that as long as the letlist doesn't change? Is the seed also related to the netlist? I end up with loads of worst case statistical corners when developing a circuit as the previous worst case statistical corners no longer produce the worst result in a later MC run if the cct has changed. Also grabbing the worst case statistical conrers for a schematic run then extracting the layout and running just the statistical corner extremes gives better results which I am aprehensive about. I still feel I need to run a full MC again as I don't believe the worst case statistical corners are still the worst case.
Statistical corners are fine if you're using process variation. If using mismatch, then they're also fine if you only change the parameters (or global variables) in the design - if you modify the circuit itself, then the mismatch won't be identical any more - because the sequence of random numbers will be affected by the differences in the circuit.