PSF format output and read the results

[anh1007]

Hi @AugustUnderground, I have a question regarding the capabilities of PySpectre. Does PySpectre support reading simulation results in PSF format, or is it limited to the nutbin format output that I am currently seeing?
Additionally, can PySpectre directly extract performance metrics such as Gain and Phase Margin similar to the Cadence Calculator, or does it only provide access to the raw waveform data?

[AugustUnderground]

Hello @anh1007. Currently pyspectre only supports the nutbin format. As such, you only get the raw waveform data. Spectre itself has no functionality for any computations with simulation results. In Virtuoso you would do this with OCEAN or the calculator in ADE, as you mentioned.

The intended scope and purpose of pyspectre is to only interface with spectre and only run simulations, nothing more. It is intentionally kept minimal like this. We do not wish to interface with Virtuoso, or re-invent waveform computations. The latter are easily implemented with native python libraries.

For reading the results there is pynut, which gives you the waveforms of the nutbin raw file as pandas dataframes in a dictionary for each simulation analyses in your netlist.

If you need to extract waveform intersection etc., you can take a look at serafin where I use pyspectre + pynut + pandas/numpy to compute almost 30 different performance parameters for single ended OpAmps based on 9 different simulation analyses in a netlist.

If you only want to read results, then there are other options for you like libpsf, psf_utils, or psf-parser.
pyspectre itself does not read files, it just calls spectre to run a simulation.

If you need to write PSF files for a singleshot simulation, then I would encourage you to contribute this functionality. Currently nutbin is hardcoded into the spectre command that will be called:

pyspectre/pyspectre/functional.py

Line 170 in 8bc990c

cmd = ['spectre', '-64', '-format', 'nutbin', '-raw', f'{raw}'

Here, you would need to parameterize the output format. If you do so, please maintain the default as nutbin to ensure backward compatibility if it is not specified otherwise.

For an interactive session, you should be able to overwrite the format in the config.yaml:

pyspectre/config.yaml

Line 5 in 8bc990c

- "-format nutbin"

Changing this from nutbin to psfbin or psfascii should have the desired effect, but I have not tested it.

[anh1007]

Hi @AugustUnderground, thank you for your respond. I did try to change the command to have format of psfbin but in the
args = ['-64', '-format nutbin', '+interactive'] line 273 in functional.py file.
I think with +interactive, it does not support psf format at all. I just wonder if you know if it supports.

Thank you!