safety0ff:
I modified the Hamming numbers code in a personal exercise.
It now uses considerably less memory but is slower.
I've posted the code here in case it is of use:
http://dpaste.dzfl.pl/3990023e5577
For a single n, n = 350_000_000:
Alternative version 2: 13.4s and ~5480 MB of ram
My code: 21s and ~74 MB of ram
I have added your version, with small changes and improvements.
I suggest to not put attributes like this:
static struct Candidate
{
typeof(Hamming.ln) ln;
typeof(Hamming.e) e;
pure nothrow:
void increment(size_t n)
{
e[n] += 1;
ln += lnprimes[n];
}
const:
bool opEquals(T)(in ref T y) {
// return this.e == y.e; // slow
return !((this.e[0] ^ y.e[0]) | (this.e[1] ^ y.e[1])
| (this.e[2] ^ y.e[2]));
}
int opCmp(T)(in ref T y) {
return ln > y.ln ? 1 : (ln < y.ln ? -1 : 0);
}
}
Bye,
bearophile
