wingo
Joined 18 years ago
Karma
1,533
Submissions
381
Member since
May 12
http://wingolog.org/
View on Hacker NewsRecent submissions
Comment · 12 years ago
Igalia, http://www.igalia.com/ -- 40+ people, 11 or 12 years old (I forget!).
A few articles I wrote on working at Igalia last year:
http://wingolog.org/archives/2013/06/05/no-master
http://wingolog.org/archives/2013/06/13/but-that-would-be-an...
Comment · 12 years ago
GC needs to know about all references in the program. If the mutator (the program) is running concurrently with the collector, it's difficult (though not impossible) for the collector to construct this consistent view.
Here is a good introductory talk: http://www.infoq.com/presentations/Understanding-Java-Garbag...
Comment · 12 years ago
That's certainly the case for full CPS, but using a CPS intermediate language does not imply call/cc. Indeed Kennedy targeted the .Net CIL; a direct-style VM. The important thing to note is that continuations and functions can be statically distinguished. The article conflates the two, which is why I don't find it very useful.
Comment · 12 years ago
I recommend Andrew Kennedy's "Compiling with Continuations, Continued" article if you are actually interested in using continuations in a production compiler. Might's formulation of CPS is good for analysis but not actually that great for code generation in my opinion. My take on the topic is here: http://wingolog.org/archives/2014/01/12/a-continuation-passi...
Comment · 13 years ago
They play this video while you wait for the train to take you up to that glacier (the mer de glace). I stared at it gapemouthed for some time!
Comment · 13 years ago
I'm pretty impressed, and especially by the apachebench test -- to serve a spike of 30K reqs/s while having 600K idle connections is quite good.
Comment · 13 years ago
You already have a programming language in your makefiles.
Comment · 13 years ago
AFAIUI libc is in the initrd, but it's a statically linked libc. Guile's dynamic FFI uses dlopen/dlsym to get its function pointers, so it can't do that in a statically linked libc. (Or could it? I suppose there's no reason why a statically linked library wouldn't expose symbol tables, whether via dlsym or some other means.)
Your point about size is well-taken though. Besides libc in this case, Guile's build products are much larger (and slower) than LuaJIT's images because we've been trying to write the compiler in Scheme from the very beginning. We can't even think about doing a nice JIT until we have a good AOT compiler, because otherwise the JIT written in Scheme would be too slow.
Comment · 13 years ago
You can redirect the control-flow of the program by overwriting a return address or a vtable. Once you've done that, it's easiest if you can redirect control to code you've written, in executable heap; but if that's not possible, you can still use return-to-libc, or potentially "return-oriented programming" strategies.
Comment · 13 years ago
Sure, it's possible. The sequence of multiplications chosen to reach the exponent is different, so these expressions take different paths through scm_integer_expt.
Comment · 13 years ago
http://git.savannah.gnu.org/gitweb/?p=guile.git;a=commit;h=2...
Fixed by Mark H Weaver, on Fri, 7 Dec 2012.
Avoid signed integer overflow in scm_product
* libguile/numbers.c (scm_product): Avoid signed integer overflow, which modern C compilers are allowed to assume will never happen, thus allowing them to optimize out our overflow checks.
* test-suite/tests/numbers.test (*): Add tests.
Comment · 14 years ago
Sounds like your problem is more that Scheme is too small for the programs you'd like to write. Implementations that are adequate to your needs being incompatible with each other is a natural side effect.
The new standard will help marginally, but there will be no grand unification of Schemes. R6RS was big enough for your needs but did not achieve wide adoption. There is no fundamental reason why this would be different for the larger R7RS report (on which work has not yet begun). Indeed, some implementations have already forked with an explicit intention of going on their own paths (Racket).
In short, for serious work, you might be able to share modules between implementations if that matters to you, but your overall application will be implementation-specific.
FWIW, IMHO, etc...
Comment · 14 years ago
An interesting perspective here:
"MCNP is written in the style of Dr. Thomas N. K. Godfrey, the principal MCNP programmer from 1975-1989 ... All variables local to a routine are no more than two characters in length, and all COMMON variables are between three and six characters in length ... The principal characteristic of Tom Godfrey's style is its terseness. Everything is accomplished in as few lines of code as possible. Thus MCNP does more than some other codes that are more than ten times larger. It was Godfrey's philosophy that anyone can understand code at the highest level by making a flow chart and anyone can understand code at the lowest level (one FORTRAN line); it is the intermediate level that is most difficult. Consequently, by using a terse programming style, subroutines could fit within a few pages and be most easily understood. Tom Godfrey's style is clearly counter to modern computer science programming philosophies, but it has served MCNP well and is preserved to provide stylistic consistency throughout."
This from MCNP4c chapter 2, section B, quoted here: http://wingolog.org/archives/2005/04/09/101. Alas, the link in that article is dead.
FWIW, I neither agree nor disagree with Godfrey's style.