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1 | /** | |
2 | * Demo: scalar.d | |
3 | * Purpose: Slightly modified source from question on [Stack Overflow](http://stackoverflow.com/questions/5142366/how-fast-is-d-compared-to-c) | |
4 | * Original code posted wasn't portable because of dynamic array length type (ulong on Linux, uint on Windows from testing) | |
5 | * Replaced platform-dependent types (array.length) with typeof and auto statements. | |
6 | * | |
7 | * Source was compiled with `rdmd --compiler=ldc2 -O3 -boundscheck=off scalar.d`. | |
8 | * Authors: @lars, Erich Gubler (@erichdongubler) | |
9 | * Date: 3/30/2015 | |
10 | */ | |
11 | import std.stdio; | |
12 | import std.datetime; | |
13 | import std.random; | |
14 | ||
15 | const long N = 20000; | |
16 | const int size = 10; | |
17 | ||
18 | alias int value_type; | |
19 | alias long result_type; | |
20 | alias value_type[] vector_t; | |
21 | alias typeof(vector_t.init.length) size_type;// Changed this to make portable - Linux is ulong, Win8.1 is uint | |
22 | ||
23 | value_type scalar_product(const ref vector_t x, const ref vector_t y) { | |
24 | value_type res = 0; | |
25 | size_type siz = x.length; | |
26 | for (size_type i = 0; i < siz; ++i) | |
27 | res += x[i] * y[i]; | |
28 | return res; | |
29 | } | |
30 | ||
31 | int main() { | |
32 | auto tm_before = Clock.currTime(); | |
33 | ||
34 | // 1. allocate and fill randomly many short vectors | |
35 | vector_t[] xs; | |
36 | xs.length = N; | |
37 | for (int i = 0; i < N; ++i) { | |
38 | xs[i].length = size; | |
39 | } | |
40 | writefln("allocation: %s ", (Clock.currTime() - tm_before)); | |
41 | tm_before = Clock.currTime(); | |
42 | ||
43 | for (int i = 0; i < N; ++i) | |
44 | for (int j = 0; j < size; ++j) | |
45 | xs[i][j] = uniform(-1000, 1000); | |
46 | writefln("random: %s ", (Clock.currTime() - tm_before)); | |
47 | tm_before = Clock.currTime(); | |
48 | ||
49 | // 2. compute all pairwise scalar products: | |
50 | result_type avg = cast(result_type) 0; | |
51 | for (int i = 0; i < N; ++i) | |
52 | for (int j = 0; j < N; ++j) | |
53 | avg += scalar_product(xs[i], xs[j]); | |
54 | avg = avg / N*N; | |
55 | writefln("result: %d", avg); | |
56 | auto time = Clock.currTime() - tm_before; | |
57 | writefln("scalar products: %s ", time); | |
58 | ||
59 | return 0; | |
60 | } |