Time on Your Side: Launching PSS Perspec Composer

We all agree that time is precious. As PSS (Portable Stimuli Standard) models get larger, the time it takes for the whole model to be loaded in Cadence Perspec Composer might become meaningful. In this blog, we will look into two practices that help you reduce this time.

Save/Restore (or the Grocery List Approach)

Most grocery shopping apps have an option to save a shopping list. This saved shopping list usually serves as a common starting point for all future shopping, including the items you usually buy. Saving the first shopping list after you spent time on it eliminates the need to look again for the same items every time. This allows users to quickly access their commonly purchased items and continue from there.

Perspec Save/Restore uses the same principle (as many other Cadence products): It saves the output of a time-consuming process to use as input for the next time. In the Perspec context, Save/Restore allows you to save the output of the model loading process (parsing the files, etc.) into a snapshot (psv file).

This snapshot file can be loaded later and serves as a starting point (just like the shopping list). In general, it is recommended to save into a snapshot the part of the model that is usually stable and is not submitted to changes often, as maintaining the versioning of the snapshots should be part of the workflow and is not handled by Perspec Composer. Note that this practice is not unique to Perspec Composer and can also be used in batch mode. This is composed of two stages:

1. Launch Perspec Composer with the Save command in batch mode. The loaded model will be saved into a snapshot (psv file). For example:
   perspec save -pss model.pss -snapshot my_snapshot.psv

2. Launch Perspec Composer with this saved snapshot using the restore command line flag. Note you can add additional parts of the model on top of it:
   perspec compose -restore my_snapshot.psv -pss my_scanrio.pss

Perspec Composer Reload (or the GTA Checkpoint System Approach)

If you have ever played the game GTA (or had your children play it), most likely you are familiar with GTA checkpoints. This gives you the possibility to save different checkpoints along your mission. Then, if you fail in your mission, you can go back to the latest relevant checkpoint and continue from there (instead of starting from scratch). Perspec Composer follows the same principle when launching. You can define a few points where you would like it to save a snapshot of the loaded files.

Let us assume you work in Perspec Composer and then you have the need to reload the model because of some changes done to the model source files. When you click on the Reload button, it will reload from the latest valid snapshot possible. Note that a Restore button is added where you can also select the checkpoint to be restored manually.

If you have not defined any checkpoints when launching Perspec Composer, clicking Reload will reload all files, and the Restore button will not be available.

For example, consider you have a small model with three PSS files: myfile_1.PSS, my_file2.PSS and my_file3.PSS. You can then launch Perspec Composer with two checkpoints (assuming the loading of each file is meaningful):
perspec compose -pss my_file1.pss -save cp1 -pss my_file2.pss -save cp2 -pss my_file3.pss

Now assume you have edited the file my_file3.pss. When you click the Reload button, Perspec Composer will detect that the most recent valid snapshot is cp2. It will then load the cp2 snapshot and load my_file3.pss on top.

You are recommended to examine the applicability of each practice to your environment to make the best of the Perspec Composer. Happy composing!