Is Unladen Swallow dead?

BartC bc at
Thu Nov 18 13:24:22 CET 2010

"John Nagle" <nagle at> wrote in message 
news:4ce37e01$0$1666$742ec2ed at
> On 11/16/2010 10:24 PM, swapnil wrote:

>> AFAIK, the merging plan was approved by Guido early this year. I guess
>> Google is expecting the community to drive the project from here on.
>> That was the whole idea for merging it to mainline. From my last
>> conversation with Collin, they are targeting Python 3.3
>     I think it's dead.  They're a year behind on quarterly releases.
> The last release was Q3 2009.  The project failed to achieve its
> stated goal of a 5x speedup. Not even close.  More like 1.5x
> (

There must have been good reasons to predict a 5x increase. But why did it 
take so long to find out the approach wasn't going anywhere?

Assuming the 5x speedup was shown to be viable (ie. performing the same 
benchmarks, on the same data, can be done that quickly in any other 
language, and allowing for the overheads associated with Python's dynamic 
nature), then what went wrong?

(I've had a look at the benchmarks, with a view to trying some on other 
languages, and they seem an extraordinarily difficult bunch to work with.)

>     The Google blog at
> "" 
> says, as of November 8, 2010:

>     So Google has pulled the plug on Unladen Swallow.  It looks
> like they underestimated the difficulty of speeding up the CPython
> model.  The performance improvement achieved was so low
> that cluttering up CPython with a JIT system and LLVM probably is
> a lose.

LLVM. Ok, that explains a lot. (LLVM is a huge, complex system).


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