08-Dec-2014 00:36, John Colvin пишет:
On Sunday, 7 December 2014 at 19:56:49 UTC, Dmitry Olshansky wrote:
06-Dec-2014 18:33, H. S. Teoh via Digitalmars-d пишет:
On Sat, Dec 06, 2014 at 03:26:08PM +0000, Russel Winder via
Digitalmars-d wrote:
[...]
primitive are passed by value; arrays and user defined types are
passed by reference only (killing memory usage)
Primitive types are scheduled for removal, leaving only reference
types.
[...]
Whoa. So they're basically going to rely on JIT to convert those boxed
Integers into hardware ints for performance?
With great success.
Sounds like I will never
consider Java for computation-heavy tasks then...
Interestingly working with JVM for the last 2 years the only problem
I've found is memory usage overhead of collections and non-trivial
objects. In my tests performance of simple numeric code was actually
better with Scala (not even plain Java) then with D (LDC), for instance.
Got an example? I'd be interested to see a numerical-code example where
the JVM can beat the llvm/gcc backends on a real calculation (even if
it's a small one).
It was trivial Gaussian integration.
http://en.wikipedia.org/wiki/Gaussian_quadrature
I do not claim code is optimal or anything, but it's line for line.
// D version
import std.algorithm, std.stdio, std.datetime;
auto integrate(double function(double) f, double a, double b, int n){
auto step = (b-a)/n;
auto sum = 0.0;
auto x = a;
while(x<b)
{
sum += (f(x) + f(x+step))*step/2;
x += step;
}
return sum;
}
long timeIt(){
StopWatch sw;
sw.start();
auto r = integrate(x => x*x*x, 0.0, 1.0, 1000000);
sw.stop();
return sw.peek().usecs;
}
void main(){
auto estimate = timeIt;
foreach(_; 0..1000)
estimate = min(estimate, timeIt);
writef("%s sec\n", estimate/1e6);
}
// Scala version
def integrate(f: Double => Double, a: Double, b: Double, n : Int):
Double = {
val step = (b-a)/n;
var sum = 0.0;
var x = a;
while(x<b)
{
sum += (f(x) + f(x+step))*step/2;
x += step;
}
sum
}
def timeIt() = {
val start = System.nanoTime();
val r = integrate(x => x*x*x, 0.0, 1.0, 1000000);
val end = System.nanoTime();
end - start
}
var estimate = timeIt;
for ( _ <- 1 to 1000 )
estimate = Math.min(estimate, timeIt)
printf("%s sec\n", estimate/1e9);
--
Dmitry Olshansky
