Denis Koroskin wrote:
On Sat, 14 Feb 2009 21:38:19 +0300, Andrei Alexandrescu
<seewebsiteforem...@erdani.org> wrote:
For 20000 evaluations over a 100000-integers array, reduce!(min),
reduce!("b > a ? b : a"), and handMax all finished within 3.4 to 3.5
seconds on my machine. The "normal" version took 11.6 seconds to
complete. Trials with various sizes reveal a similar pattern
throughout: pass-by-delegate is way behind the others, which work
about as fast.
This means that, had std.algorithm taken the "normal" route, it would
have been plenty useless for any serious needs. Not taking the
"normal" route means that its abstractions rival hand-tuned code so I
can use them without worrying they will come unglued when shown a real
challenge.
So, to paraphrase the ugly guy in "The Good, The Bad, and The Ugly":
If you want to shoot, shoot, don't troll.
Andrei
Did you try passing a comparator (C++ way to do things)? It should be
pretty fast, to.
Is this what you meant?
struct StructMax
{
static uint opCall(uint a, uint b)
{
return b > a ? b : a;
}
}
uint reduceStruct(uint[] x, StructMax s)
{
invariant n = x.length;
uint m = x[0];
for (uint i = 1; i < n; ++i) {
m = s(m, x[i]);
}
return m;
}
I did, and as expected the running time is similar to the other fast
approaches. Removing "static" does not affect the timings sensibly.
Andrei
