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<@U01819B63HP> Is there any setting in xschem-ngspice to increase `TRAN` simulation runtime by using more CPU cores or multi threading ?

Any option to reduce `.raw` file output size? For certain simulation it is forming into GB which takes time to load waveforms.

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raw size is reduced by saving a selected set of variables. This means:
• do not use `.options savecurrents`
• do not use `save all` (or `.save all`) 
• explicitly tell what you want to save, by adding `save v(xxx) i(xxx) .....` lines
To indicate voltage nodes you want to save you can use the `spice_probe.sym` component. This will automatically add the .save ... instruction for you.

You should have a `.spiceinit` file in the directory where ngspice runs simulations. this line:
`set num_threads=4`
tells ngspice to use more threads.
Don't be too optimistic, the solver is not parallel, increasing threads will give no benefit for the solver. More threads are used to evaluate device equations that usualy takes 50% of total simulation time. Above 4 threads there are no significant advantages in my tests.