extradoc / sprintinfo / mallorca / mallorca-sprintreport.txt

Hi all!

This is the first report of the challenging Mallorca sprint. On the one 
hand getting here proved to be quite an ordeal for some of the sprinters 
due to bad weather at airports and uncooperative ferry companies. On the 
other hand it seems that we have finally run out of even vaguely easy 
tasks to do and are thus involved in serious head-scratching and the 
making of strange noises as we contemplate what we have to do.

The sprint is hosted in the GNU/Linux lab of the Universitat de les 
Illes Balears in Palma de Mallorca. We are very thankful to them for 
letting us disturb their undergraduates in their attempts to use the 

On the first day some of the strangest noises were produced by Samuele 
who started together with Gerald and Stephan to work on a static version 
of ctypes for rpython. On Tuesday evening, after lots of tedious work on 
all levels of the translation toolchain, they managed (with some 
cheating) to got an example calling atoi to run.

Michael and Arre started extending the l3interpreter to support 
operations involving heap-structures in a way that could be run on top 
of the llinterpreter and after translation to C. After some argument 
with Samuele, who, as usual, turned out to be right, they were 
successful in their goals. This means that the l3intepreter can now 
perform reasonably complex operations involving pointers but not 
subtract two integers.

Carl Friedrich and Richard started refactoring the gc framework to use 
the new facilities Michael and Arre had written. Progress there was 
extreeeemely slow, so that in the evening of the first day only marginal 
progress was achieved.

Christian, Eric and later Jacob started exposing PyPy's stackless 
features to application level. While doing this they found a few 
problems in the interp-level code and refactored it a bit. On the second 
and third day Christian and Jacob continued with this. They managed to 
expose simple coroutines on Wednesday and are now continuing to create 
nicer interfaces following the stackless module of stackless Python. One 
of the problems there turned out to be testing turnaround time, since 
the functionality can only be tested after a full translation has been 
run. There might be some ways around this involving slimy hacks.

On the second day most pairs continued as before. Armin and Carl 
Friedrich worked on the JIT. They started defining an interface to 
generate code at runtime (see 
and then using this same interface in the low level abstract 
interpreter. This turned out to be quite difficult in the sense that 
most of the time was spent re-redesigning the interface yet another time.

On the third day Armin swapped with Samuele and continued with Gerald 
and Stephan to work on rctypes, with slow but steady progress. They are 
now able to annotate simple cases that use structures.

Arre and Samuele tied themselves to the JIT treadmill and continued the 
work of Armin and Carl. A lot of "wuah!"'s and "arrgh!"'s can be heared 
from their direction -- we assume they are having fun.

Carl Friedrich and Michael thought about how to integrate the currently 
only simulated GC framework with the backends. This looked and still 
looks like it will be *a lot of* work but they were able to at least 
clarify some issues and get somewhat started.

Eric and Richard tried to finally remove the dependency on pyrex (!) in 
genllvm which is a relict from the old days of the first LLVM backend 
(which was pre-rtyper!). They are also working on removing some 
hand-written C code from genllvm.

So while we're not seeing super-rapid progress there are still 
interesting changes continuously arriving. Tomorrow is a day off, but 
given the bunch of obsessives we are there might still be some checkins. 
There will still be three full days of sprinting afterwards.

Cheers from sunny Palma,

Michael & Carl Friedrich

We greet you once again from the Aula Linux lab of the UIB in Palma de
Mallorca.  There is one more day of sprinting, but as many people have
had to leave slightly early, it's probably safe to attempt some kind
of summary.

Thursday was the break day, which didn't stop some mad people from
doing a little work on rctypes and the JIT.  The sane ones among us
went hiking or to artists' studios instead :)

Friday was not the most productive of days, partly becase we gave a
talk to some people from the university and the local free software
user group in the afternoon.  Also contributing to the lack of results
were the general difficulty of the tasks and some amazing getting-lost
skills ("getting lost" here refers to the physical world for a change).

Armin, Arre and Samuele worked on the JIT, the idea being to write an
"abstract abstract interpreter", which would specialize an abstract
interpreter of low-level graphs for a particular set of low-level
graphs.  At lunch they told a hilarious joke that they weren't going
to do this at all and would instead re-use the annotator to extract
the needed information.  This then turned out to not be a joke at all,
and is exactly what they did for the next two days (apparently they
plan to re-use the rtyper as well, but this is just preposterous).

Christian worked on coroutines and other stackless-like functionality,
with good results: you can now build a version of pypy that can use
and freely intermingle raw coroutines, tasklets and greenlets all at
once.  Apparently this is all fairly natural in the implementation,
but must allow for the possibility of some *deeply* obscure user
code... (obfuscated pypy contests, anyone?)

Michael and Carl repeatedly bashed their heads onto the topic of gc
integration, the desk, reference counting details, walls, genc and so
on.  The basic goal was to express the logic behind placing incref and
decref operations as a nice and fairly clear transformation of the
flow graphs, as opposed to backend-specific incomprehensible hacks.
This task was made considerably harder by exceptions (who uses them,
anyway?) but hopefully by the time we've finished writing this report
we'll have built a pypy-c in the new style.  This work should allow
(finally) the integration of the GC framework Carl wrote as his Summer
of Code project, and mere mortals to understand genc.

Gerald and Stephan continued to work on "rctypes" -- a static version
of ctypes for RPython.  Reasonably complex ctypes declarations can now
be annotated.

Eric and Richard worked on a transformation to replace some of the
operation that can raise exceptions with direct_call operations --
something that will be very useful for the GC work mentioned above,
because operations that can raise an exception need special treatment
-- so the fewer the better!

And finally, some really interesting news: Armin plans to release
Bub-n-Bros 1.5, the play testing of which delayed this morning's
status meeting considerably :)

To sum up, this sprint has seen a fair amount of work on very
challenging tasks.  As usual we all need to sleep for a week, so it's
time to leave this wonderful island (also, it's raining).

mwh and Carl Friedrich