Checkpoint - Restart (checkpoint)

Description

Spectre has the ability to save the checkpoint files generated during analyses, and to restart an analysis from its checkpoint file. Checkpoint files can be generated in the following ways:

• Periodically, based on real time (wall clock time).
• Asynchronous UNIX signals.
• By other methods unique to the analyses.

To generate checkpoint files periodically based on real time, set the Spectre option ckptclock to the time interval, in seconds. This option is turned on by default with a value of 1800 seconds (30 minutes). Spectre deletes the checkpoint file if the simulation completes normally. If the simulation terminates abnormally, the checkpoint file is not deleted.

If Spectre receives the UNIX signal USR2, Spectre immediately writes a checkpoint file. If Spectre receives interrupt signals, such as QUIT, TERM, INT, or HUP, Spectre attempts to write a checkpoint file and then exits. For other fatal signals, Spectre may not write a checkpoint file.

The name of the checkpoint file is a combination of the circuit name and the analysis name with the extension.ckpt. For example, if the circuit is named test1 and the transient analysis is named timeSweep, the checkpoint file is named test1.timeSweep.tran.ckpt.

Spectre keeps only the latest checkpoint file. It creates a new checkpoint file with a temporary name. After the file is successfully written, Spectre deletes the previous checkpoint file created earlier and renames the new file.

Currently, only transient analysis supports checkpoint files and restart.

Checkpoint

Transient analysis can generate checkpoint files periodically based on the transient simulation time. This is done by using a transient analysis parameter named ckptperiod, which is turned off by default. To enable the checkpoint feature, the argument +checkpoint must be added to the spectre command.

Restart

To restart an analysis from a checkpoint file, use the +recover option with the spectre command. Spectre searches the analyses log for the checkpoint file. If the checkpoint file for the analysis exists, Spectre skips over any previous analyses, and restarts the analysis by using the information from the file.

For more information, see Recovering From Transient Analysis Terminations section in the Spectre Classic Simulator, Spectre APS, Spectre X, and Spectre XPS User Guide.

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