On Wednesday, 31 July 2013 at 22:23:54 UTC, bearophile wrote:
Justin Whear:
If anything, component programming is just functional
programming + templates and some nice syntactic sugar.
And a healthy dose of pure awesome.
What D calls "component programming" is very nice and good, but
in D it's almost a joke.
Currently this code inlines nothing (the allocations, the
difference and the product):
import std.numeric: dotProduct;
int main() {
enum N = 50;
auto a = new int[N];
auto b = new int[N];
auto c = new int[N];
c[] = a[] - b[];
int result = dotProduct(c, c);
return result;
}
If you write it in component-style (using doubles here):
import std.math;
import std.algorithm, std.range;
int main() {
enum N = 50;
alias T = double;
auto a = new T[N];
auto b = new T[N];
return cast(int)zip(a, b)
.map!(p => (p[0] - p[1]) ^^ 2)
.reduce!q{a + b};
}
The situation gets much worse, you see many functions in the
binary, that even LDC2 often not able to inline. The GHC
Haskell compiler turns similar "components" code in efficient
SIMD asm (that uses packed doubles, like double2), it inlines
everything, merges the loops, produces a small amount of asm
output, and there is no "c" intermediate array. In GHC
"component programming" is mature (and Intel is developing an
Haskell compiler that is even more optimizing), while in
D/dmd/Phobos this stuff is just started. GHC has twenty+ years
of head start on this and it shows.
The situation should be improved for D/dmd/Phobos, otherwise
such D component programming remains partially a dream, or a
toy.
Bye,
bearophile
I was honestly thinking whether I should reply to this rant or
not... Obviously I picked the first. - Component programming, as
you probably know yourself already, is not about making
super-fast, super-optimized applications, but about making it
easy both to write the code and to understand the code, as well
as making it easy to combine components (algorithms mostly) and
get the result quickly, where by "quickly" I think about time I
need to write the code.
If you really want a super-optimized solution you will in most
cases write the piece in question in C. Well, that is at least
what my experience tells me. Luckily, I do business applications
most of the time, so performance is rarely an issue. CONVENIENCE
is! In other words, I shamelessly admit, I only care about the
time I have to spend coding in order to implement something that
is of value to the business.
