Christopher Wright wrote:
Jeremie Pelletier wrote:
language_fan wrote:
Wed, 23 Sep 2009 10:43:53 -0400, Jeremie Pelletier thusly wrote:
You're right about concurrency being a different concept than
threading,
but I wouldn't give threading away for a pure concurrent model
either.
I believe D is aiming at giving programmers a choice of the tools they
wish to use. I could see uses of both a concurrent model with message
passing and a threading model with shared data used at once in a
program.
The danger in too large a flexibility is that concurrency is not easy
and it is getting incresingly complex. You need to be extraordinary
good at manually managing all concurrent use of data. If I may
predict something that is going to happen, it is that there will be
high level models that avoid many low level pitfalls. These models
will not provide 100% efficiency, but they are getting faster and
faster, without compromizing the safety aspect. This already happened
with memory allocation (manual vs garbage collection - in common
applications, but not in special cases). Before that we gave some of
the error detection capabilities to the compiler (e.g. we do not
write array bounds checks ourselves anymore). And optimizations (e.g.
register allocation). You may disagree, but I find it much more
pleasant to find that the application does never crash even though it
works 15% slower than an optimal C++ code would.
15% slower is an extreme performance hit. I agree that code safety is
useful and I use this model all the time for initialization and other
code which isn't real time, but 15% takes away a lot of the
application's responsiveness, if you have 50 such applications running
on your system you just spent $1000 more in hardware to get the
performance of entry level hardware with faster code.
What are most applications these days? MS Office, a web browser, maybe
an email client, some odds and ends, and a whole bunch of web sites
running on servers somewhere (with associated database servers and some
other odds and ends).
How much does it cost to get a slightly better machine? Fully hosted?
Maybe $100/month.
How much does it cost to develop it in a faster but more error-prone
language? Maybe months more time to market, time you're not making money
but are still paying developers. Those developers will need to be more
skilled than the ones using a safer language, and thus will cost you
more. New features will take more time to develop.
It's a competitive advantage to use a slower, safer language on the web.
Desktop applications are not quite so straightforward.
I agree with you about web applications, scripting languages are fast
enough to serve web pages in most cases. However I did see some pretty
ugly code which took over a minute to generate a page from a 1.5Gb
database using only string fields without any indexes and PHP was
throwing more notices and warnings than actual html.
I was referring to desktop applications, where you can't just buy a
second server to host your database and serve static content like images
and whatnot. From the 2 years I worked in tech support the problem I saw
the most often was computers slowed down to a crawl, many of them
without viruses or spywares. There are so many people who upgrade their
computer just so they can run new software that really doesn't have many
new features, but just is written in a safer language. That 15%
performance hit over all the programs they ran at once was just too much
for their old processor, when 2 months ago before they upgraded the
software it was working just fine. Live messenger should not take half a
minute to load and perform poorly when the old msn messenger was running
perfectly fine.
If you wrote a real time renderer for example with that 15% hit, you
get a very noticeable difference in framerate. Not to mention standard
GUIs to be laggy on slower machines (just MSN messenger runs to a
crawl on my old computer, yet it can run the first UT which does way
more operations per second, because there's no performance hit by
safer code bloat).
Games are not interesting in this regard. They require performance, and
they're hideously expensive. A studio can throw developers at the
problems and make them go away.
Not all games are like this, of course. But most are.
<rant>
What happened to one man armies like John Carmack and Tim Sweeney? These
were the guys who inspired me to get into coding in the first place. I
just loved how they could put together entire engines on their own and
carefully optimize them. What about Walter who wrote the first C++
compiler and optlink as well as dmd from which I learned so much about
compiler internals, or Andrei and his extensive work on meta programming
and generic programming, from which I also learned so much.
There's also that one guy developing the game LOVE all on his own using
only C, he wrote his tools, his engine, his model format, does his
artwork, *everything*. And he is making some quick progress that would
make teams of 50+ jealous.
Point is, only companies have the resources to throw more people at the
problem and forget about it. At the end of the day, if you multiply the
number of people involved by the development time, the one man army
still is winning by far, both in time and resources spent.
Games were only an example, what about programs like flash, photoshop,
autocad, 3dsm, and others. No matter what domain you're interested in
you're gonna come across program that require every bit of performance
they can get. Be it developed by teams of 50+ programmers or a single one.
I'm not saying safer languages are bad, far from that, I'm just saying
there's a way to get the productivity of these languages and the
optimization power of unsafe languages together, and there's a target
audience for that.
Having a single language which provides enough features to allow either
safe development or unsafe development will also get everything in
between. This is what got me hooked on D in the first place, even when I
first read about it this is what was going through my head, and I
haven't looked back since.
</rant>
Jeremie.
