Re: Voting For std.experimental.ndslice

[Jack Stouffer via Digitalmars-d]

On Wednesday, 30 December 2015 at 00:24:38 UTC, Ilya Yaroshenko 
wrote:
Awesome!

Please find my notes below.

Thanks for the feedback. Good thing I posted this here before 
releasing it.

Funny thing, when I made the D example use the mean lambda 
function, it got way faster. Even with the larger array size, the 
D code went from 138 ns with the small array and the function to 
58 ns with the large array and the lambda. And, the Python code 
expectantly got slower, even when I made sure to only test the 
np.mean function, the time taking the mean of the large array was 
145 µs up from 10.5 µs with allocation and taking the mean with 
the smaller array.

So now the D version is 2474x faster.

Also, I was unable to get LDC numbers, as when I compiled my test 
program with all of the optimization flags, LDC returns 0 hnsecs

the code:

===============

import std.range;
import std.algorithm.iteration;
import std.experimental.ndslice;
import std.stdio;
import std.datetime;
import std.conv : to;

void f0() {
    auto means = 100_000.iota.sliced(100, 1000).transposed.map!(r 
=> sum(r) / r.length);
}

void main() {
    auto r = benchmark!(f0)(10_000);
    auto f0Result = to!Duration(r[0]);
    f0Result.writeln;
}

I'm assuming that LLVM realizes that the variable means is never 
used, so it removes it from the final version.