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 The Breker Trekker

Posts Tagged ‘SystemVerilog’

Path Constraints for Graphs and Portable Stimulus

Thursday, May 19th, 2016

As engineers, we take great pride in defining our terms carefully and using them precisely to try to avoid ambiguity or confusion. Many engineering specifications start with a glossary of terms and sometimes even a taxonomy showing how they are related. Sometimes though, natural language being inherently ambiguous, we find that we have overloaded the meaning of certain words in a way that can lead to precisely the confusion we seek to avoid.

One such word is “constraint” because it is used in several different contexts in chip design and verification. In today’s post we would like to discuss path constraints on a graph-based scenario model. We will explain how they differ from other forms of constraints and why path constraints are essential for any portable stimulus solution, including the Trek family of products from Breker.

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The Report of Simulation’s Death Was an Exaggeration

Thursday, May 5th, 2016

With a nod to Mark Twain, this week I’d like to comment on a recent threepart series with the provocative title “Are Simulation’s Days Numbered?” The articles were transcribed from one of the “experts at the table” events that SemiconductorEngineering does so well. Breker wasn’t involved in this particular roundtable, but I enjoyed reading the series and found that it stirred up some thoughts. As a blogger, of course I’m going to share them with you and I hope you enjoy them in turn.

Let’s get this out of the way immediately: in three parts and more than 5,000 words, there was no mention of portable stimulus. That might not seem too surprising given the title, but in fact verification portability both from IP to system and from simulation to hardware arose during the discussion. So I’ll comment on that but, given my background as a vendor of formal EDA tools and reusable IP blocks, there are a few other topics that also piqued my interest.

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Catching Up with Portable Stimulus

Tuesday, April 26th, 2016

Ever since Accellera started the Portable Stimulus Working Group (PSWG), this emerging technology has generated a lot of buzz both within the EDA industry and among our semiconductor and systems customers. As the pioneer in this technology we get a lot of questions about what portable stimulus is, why it is different from the Universal Verification Methodology (UVM) and other established approaches, and why anyone would need it.

We’ve devoted quite a few posts to this topic in The Brekker Treker blog, stretching back two years to when Accellera first set up a proposed working group (PWG) to survey the industry and decided whether standardization of portable stimulus was feasible and desirable. Given the many posts scattered throughout the past two years, we thought that we would take this opportunity to give readers new to this topic a guided tour of the information that we have available.

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A Portable Stimulus Standard Will Take Time, but the Technology is Here Today

Thursday, March 24th, 2016

Last week, we used an update on the Accellera Portable Stimulus Working Group (PSWG) presented at the Design and Verification Conference and Exhibition (DVCon) as a jumping-off point to discuss the status of this standardization effort and some key aspects of the three proposals currently under consideration. We were not the only blog to cover portable stimulus topics from DVCon; Brian Bailey of SemiconductorEngineering and Bernard Murphy from SemiWiki also posted their observations.

Earlier this week, EDACafe blogger colleague Peggy Aycinena posted a thought-provoking look at PSWG and the portable stimulus challenge. In regards to the scope of the proposed standard, she noted “a distinct wow factor in all of this, it’s so comprehensive” and said “this whole effort seems massive to me.” Today we’d like to respond to Peggy’s comments and questions, noting both the challenges of a portable stimulus standard and the availability of a working solution today.

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A Snapshot Update on the Accellera Portable Stimulus Effort

Wednesday, March 16th, 2016

As all of our regular readers are aware, the software-driven SoC verification space pioneered by Breker is becoming more of a mainstream approach every day. One good barometer for the industry shift now underway is the standardization effort in progress within the Accellera Portable Stimulus Working Group (PSWG). The amount of interest in this standard has skyrocketed recently, and portable stimulus was a hot topic at the Design and Verification Conference and Exhibition (DVCon) two weeks ago.

As we promised when we first began discussing the PSWG, we don’t believe in sharing internal details of standardization work in a public blog. However, the group was offered a slot to present an update at an Accellera-sponsored lunch during DVCon. So the PSWG put together a set of slides with information to share publicly and Vice-Chair Tom Fitzpatrick of Mentor did a nice job of presenting them. For those of you who could not attend, we’ll summarize the current status in today’s blog post.

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Why C/C++ Is the Lingua Franca for Verification

Tuesday, November 17th, 2015

In last week’s post, we dissected the results for verification languages and methodologies from a recent survey by Mentor Graphics and Wilson Research Group. The main result was that SystemVerilog is growing in popularity on all fronts, but we observed that C/C++ has a significant presence. We also argued that the survey’s focus on simulation likely resulted in C/C++ being under-represented since these languages are widely used for verification with hardware platforms and for silicon validation in the lab.

We see C/C++ as the common link for many types of programming activities, and so widely known that many consider it the lingua franca of software. Just type “lingua franca C/C++” into your favorite search engine and scan the results for some interesting arguments and a few counter-arguments. To be fair, some observers consider C the lingua franca and downplay C++. We tend to group them together since object-oriented programming is now widespread and so moving from C to C++ should be a natural transition.

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Verification Languages: Tower of Babel?

Wednesday, November 11th, 2015

One of the cliches we hear from time to time in the industry is “designers want to stick with a single language, but verification engineers love learning new things.” The implication seems to be that because verification engineers have diverse jobs that require them to juggle lots of different tools and models, they necessarily have to learn new languages and methodologies on a regular basis. Of course, they may not actually love learning new languages; doing so may just be in the nature of their work.

Regardless of whether or not they “love” new languages, it is clear that most verification projects involve multiple languages and multiple approaches. One way to gauge the current situation is to turn to the excellent survey that Mentor Graphics performs with Wilson Research Group every couple of years. Harry Foster wrote a series of posts on the Mentor verification blog that give considerable insight into what verification (and design) engineers are doing on real projects.

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Riding the Portable Stimulus Wave

Wednesday, September 16th, 2015

Last week, we discussed the details of a noteworthy press release that we issued with Cadence and Mentor Graphics announcing a joint contribution to the Portable Stimulus Working Group (PSWG) of Accellera Systems Initiative. As we expected, this release stirred up a lot of interest in portable stimulus. The timing was perfect, both because of today’s deadline for contributions to the PSWG and because of last week’s DVCon India conference. I’d like to provide some updates on both activities.

First of all, the three companies did upload our joint contribution document to the PSWG internal Web site today in time for the deadline. Please note that, as per the rules for Accellera and most other standards groups, working documents are not available to the general public. If you’d like to see the contribution and follow the evolution of the standard, please consider joining the PSWG. If your company is not yet a member of Accellera, then please alert your standards manager to the benefits of participation.

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Breker, Cadence, and Mentor Accelerate Portable Stimulus Standard

Tuesday, September 8th, 2015

This morning, Breker issued a press release with Cadence and Mentor Graphics announcing a joint contribution to the Portable Stimulus Working Group (PSWG) of Accellera Systems Initiative. We expect that this news may be surprising to much of the EDA world, so we’d like to take today’s post on The Breker Trekker to fill in some background and offer you the opportunity to ask questions. Please note that we are speaking only for Breker in this post although we doubtless share many opinions with our co-contributors.

Let’s start with a quick summary of how Accellera works so that all readers understand the context for this major contribution. The portable stimulus effort started with a Proposed Working Group last year that assessed the interest in a standard and defined a set of more than 100 requirements that such a standard would have to satisfy. Accellera approved the formation of the PSWG and we began meeting in March of this year. We have refined the requirements list and also developed a set of “use cases” showing the sort of real-world verification problems that a standard would have to address.

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Portable Stimulus Layer 3: Test Randomization

Thursday, May 28th, 2015

Over the lifetime of this blog, we’ve covered a lot of diverse topics regarding Breker’s products and technology, trends in SoC verification, and the EDA industry in general. For the last month, we’ve offered our longest series of posts ever on a single topic: portable stimulus. There’s a very good reason for this: Accellera’s Portable Stimulus Working Group (PSWG) is making good progress on defining a standard in this area. As one of the group’s leaders, Breker has been leveraging our many years of experience in SoC verification to develop the best possible industry solution. We’ve been using The Breker Trekker blog to share our thoughts and to encourage your feedback.

We begin the fifth, and perhaps most important, post in our series by reminding you that we split portable stimulus into three layers: defining the tests using abstract primitive operations, scheduling the tests across multiple threads and multiple processors, and randomizing the control flow to verify the full range of realistic use-case scenarios. We have shown over the last two posts that both the first and second layers can be defined easily by a simple application programming interface (API) providing access to a base-class library. This library includes the basic building blocks needed for a directed or automated test as well as scheduling control for processors, threads, and resources. It is natural to wonder whether the randomization layer can be handled in a similar way.

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