( ESNUG 477 Item 10 ) ------------------------------------------- [11/20/08]
Subject: ( ESNUG 475 #10 ) Bluespec is the "biggest lie in ESL space"
> "(optional) -- What were the WORST tool[s] or the biggest LIE[s]
> you heard at DAC? You can be anon here, but please be specific."
From: Sandeep Shukla <shukla=user domain=vt.edu>
I will just say what is the biggest lie in ESL space. It is Bluespec and
their entourage.
First of all, they are not ESL, because they specify design at the level
of register transfer, with the exact register/state elements already
specified by the designer. The only thing they provide are rules that are
atomic (each rule is an @always block in Verilog except that in Verilog you
are not guaranteed atomicity during simulation, but in real hardware the
atomicity is not even relevant because there is no interleaving when real
hardware executes).
The examples Bluespec shows to designers are contrived. Consider their
2x2 switch example, where they model the design by making rules for each
input rather than what is natural -- make rules on each output variable.
Also, Bluespec requires that the designers think differently (not so
different than a good Verilog designer) but if a company's internal DA
wants to make templates for Verilog design style and make lint tools so
that if a designer violates the design style guides, it will not be
passed to compiler, then the effect will be the same.
Bluespec does not have a formal semantics contrary to their claim. There
has been multiple attempts inside the company and at MIT to provide formal
semantics, but they failed due to various features such as "regwires"
added to Bluespec by the company making the language less clean for a
suitably formal semantics.
Bluespec is actually a rip off on existing ideas such as UNITY language for
Parallel Programming by Chandy and Mishra, and Abstract State Machine (ASM)
by Gurevich who is now at Microsoft. Bluespec people know this, but almost
never acknowledge that, and call their technology "big deal from MIT" to
attract investors.
So in summary, I think the Bluespec will never make it, but the company is
in denial mode.
- Sandeep Shukla
Virginia Tech Blacksburg, VA
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