Monday, October 14, 2013

Trishool for verification

It’s the time of the year when I try to correlate Mythology with Verification. Yes, festive season is back in India and this is the time when we celebrate the fact that good prevails over evil. Given the diversity of Indian culture, there are a variety of mythological stories about demigods taking over evil. Well for us in the verification domain, it is the BUG that plays the evil preventing us from achieving first silicon success. While consumerism of electronic devices worked wonders in increasing the size of business, it actually forced the ASIC teams to gear up for developing better products in shrinking schedules. Given that verification is the long pole in achieving this goal, verification teams need a solution that ensures the functionality on chip is intact in a time bound fashion. The rising nature of design complexity has further transformed verification into a diverse problem where a single tool or methodology is unable to solve it. Clearly a multi pronged approach.... a TRISHOOL is required!
TRISHOOL is a Sanskrit word meaning 'three spears'. The symbol is polyvalent and is wielded by the Hindu God Shiva and Goddess Durga. Even the Greek God of sea Poseidon and Neptune  the Roman God of the sea, are known to carry it. The three points have various meanings and significance. One of the common explanations being that Lord Shiva uses the Trishool to destroy the three worlds: the physical world, the world of culture drawn from the past and the world of the mind representing the processes of sensing and acting. In physical sense, the three spears would actually be fatal as compared to a single one. 
So basically we need a verification strategy equivalent to a Trishool to confirm that the efforts converge in rendering a fatal blow to the hidden bugs. The verification tools available today correlate well with the spears of Trishool and if put together would weed out bugs in a staged manner moving from IP to SoC verification. So which are the 3 main tools that should be part of this strategy to nail down the complex problem we are dealing with today?
Constrained RandomVerification (CRV) is the workhorse for IP verification & reuse of the efforts at SoC level makes it as the main spear or the central spear of the verification Trishool strategy. CRV is further complimented by the other two spears on either side i.e. Formal Verification and Graph based Verification. The focus of CRV is more at the IP level wherein the design is stressed under constraints to attack the thought through features (verification plan & coverage) and also hit corner cases or areas not comprehended. As we move from IP to SoC level, we face two major challenges. One is repetitive code typically combinational in nature where Formal techniques can prove the functionality comprehensively and in limited simulation cycles. Second is developing SoC level scenarios that cover all aspects of SoC and not just integration of IPs. The third spear or graph based verification comes to rescue at this level where multi processor integration, use cases, low power scenarios and performance simulations are enabled with much ease. 
Hope this festive season while we enjoy the food & sweets, the stories and enacts that we experience around will also given enough food for thought towards a Trishool strategy for verification.
Happy Dussehra!!!
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  1. Jitesh Shah, Sr. Manager, Logic VerificationDecember 4, 2013 at 6:08 AM

    Nice correlation. "Graph based verification" caught my attention and wondering how realistic it is in today's UVM based TB environment. I am paying attention to what Mentor is presenting over last couple years and it's pretty interesting technology but key question is how real and practical it is..? Anyone who has evaluated this can share their experiences here. Thanks. Jitesh

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