Custom IC Design Blogs

Virtuoso ADE Assembler has always been a trusted tool to run simulations for analog or mixed-signal designs, but in scenarios that involve a large number of simulations, you must have seen situations where you need to:

• Run simulations that continue for days and you wonder what is the ICRP process doing while simulations are running
• Avoid display/IO and other random errors that are shown when the number of jobs increase
• Run thousands of sweeps or corners or Monte Carlo samples for design verification and you wonder if you could launch thousands of netlisting and simulation jobs
• Flexibly distribute netlisting and simulation jobs separately on separate machine networks
• Set up a better resource management with lighter processes to monitor simulation processes or to evaluate expressions

In Virtuoso IC6.1.8 ISR14 and ICADVM20.1 base releases, a new job control mode, Large-Scale Cloud Simulation (LSCS), has been introduced. This job control mode is highly scalable and can handle thousands of netlisting and simulation jobs in parallel. LSCS supports all job distribution methods available in the Virtuoso ADE Explorer and Virtuoso ADE Assembler environments and also enables future scalability requirements, mainly for cloud simulations.

Features of LSCS

LSCS is a next-generation job control architecture specifically geared towards:

• Increasing simulation throughput with large simulation point handling
• Increasing software robustness
• Smarter debugging capability

All of these can be achieved through the following set of features of this new architecture:

Architecture of LSCS

So what enables all these great features in LSCS? It is the robust architecture that comprises many components that coordinate with each other to control different parts of a simulation run. These systems work independently and concurrently with a set of shared queues of messages.

Let's take a closer look at the architecture of LSCS job control mode in detail.

It contains the following components:

• Netlist Service: Runs dedicated jobs to create netlists for data points.
• Spectre Monitor: Runs dedicated jobs to run simulations.
• Expression Evaluator: Runs jobs to evaluate expressions based on the simulation results.
• Message Queues: Enable communication between the three components mentioned above. These queues work on producer-consumer model where a producer process places a task in a message queue. The consumer process processes the tasks in the message queue whenever it is free from its existing tasks. No process is left waiting for the other process to complete the communication.
• Logging Service: Drives message exchanges between message queues.

Setting Up and Running Simulations Using LSCS

As different processes handle netlisting and simulation in this mode, you have the control to set up different job policies for netlisting and simulation. That means, you have separate tabs in the Job Policy Setup form to set up netlisting and simulation jobs. You also have a separate set of environment variables to control the settings for LSCS and to set up default job policies for each type of jobs.

SKILL functions are also available to identify the netlisting and evaluator process, to customize the startup file, and to load only the required files for the respective processes. 

Debugging LSCS Job Control Mode

LSCS provides advanced debugging capabilities. A new and advanced Log Viewer interface is available to view the consolidated logs for the run. It provides filtering capabilities based on the message type: info, warning, or error. You can also filter messages based on a search string. The log entries that meet the filtering criteria are highlighted and filtered. Enhanced messages are displayed to identify the stages of the run and identification of the issues.

The checkSysConf utility can be enabled to run automatically on the simulation host and the report is made available in the job log file. 

Hope this interests you to learn more about LSCS. Watch the videos listed in the Related Resources section below. 

Related Resources

For more information on Cadence circuit design products and services, visit www.cadence.com.

Contact Us

For any questions, general feedback, or even if you want to suggest a future blog topic, write to custom_ic_blogs@cadence.com.

Happy reading!

Amit Bajaj and Amit Sanadhya

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