Open Source EDAs
11 posts
PyVSC Meets Dataclasses
The last post ended with a number that a solver can't explain. Switching PyVSC to dv-solve took riscv-dv's Python generator from 128 to 474 instructions a second, without changing pygen. Porting pygen's instruction classes to a new front-end took it to 6,553, …
DV-Solve: A Random-First Solver
len 8 -- feeds two front-ends, PyVSC 1.0 (Python, in-process) and Verilator 5.054 (SV randomize()). Both lead to a dark card: dv-solve, same packet both ways: about 140 times the draws per second of Boolector in PyVSC, about 6 times the bundled Bitwuzla in Ve…
Revisiting PyVSC: Where we Stand
PyVSC started in 2019 with a simple goal: make SystemVerilog-style constrained-random stimulus and functional coverage feel as natural in Python as they do in SystemVerilog. I wrote about it in early 2020, in a series that started with [Modeling Random Stimulu…
Open Source PSS: Checking Beyond the LRM
Compilers check whether source code is legal according to the language reference manual (LRM). But legal isn't the same as right. A model can be perfectly legal PSS and still use a library in a way that can't work, or ignore conventions that the rest of your t…
Open Source PSS: Formatting
It's no surprise that well-formatted text is easier to read, and that's as true of code as it is of prose. But keeping code well formatted by hand is tedious, and it costs more than it would seems. Whitespace diffs obscures legitimate changes, and review comm…
Open Source PSS: PSSParser
We've spent the last few posts looking at some of the new features in the public review draft of PSS 3.1. We'll spend the next few looking at some open-source tools that can help as you adopt PSS. First up is a parser that forms the foundation of several othe…
PSS 3.1: Target Runtime
The two ways a PSS description connects to a platform have very different tradeoffs. Target-code generation -- last post's subject -- gives you fine-grained control over the syntax of the code that implements a test; it treats PSS as a language for generatin…
PSS 3.1: Target Code
A PSS description has two fundamental ways of interfacing with a platform: by specifying the APIs to call, or the code to generate. We'll talk more about the API-based approach in the next post, but for now we focus on what's new with target-code generation in…
PSS 3.1: Simplifying Composition
A PSS description is structure, in much the same way that hardware is structural. Even PSS activities are visualized as UML diagrams -- which have a certain structure to them. The next category of features to look at in PSS 3.1 are features that help to simpli…
PSS 3.1: Simplifying Constraint Modeling
PSS language constructs fall into two main categories: declarative and procedural. When you see 'declarative', think 'rules' and 'constraints'. A declarative description is captured in terms of boundaries and relationships that must hold for the description …
PSS 3.1 Is Out for Public Review -- Here's What Changed
After roughly two years of work, the Accellera Portable Stimulus Working Group (PSWG) released PSS 3.1 for public review. PSS 3.1 is a so-called 'minor' release, which is always a bit subjective. PSS 3.1 doesn't introduce major new features, the way that PSS …