[英]Why is my Rust program running more that twice as slow as the Java equivalent?
我有一個程序,對於小於或等於輸入的所有整數,找到可以表示為兩個立方體之和的數字,兩次,即拉馬努金數問題。
我已經在ZD523878880EE1EA22817A72D3759213819Z和ZF5E265D607CB720058FC166E00083FEE8Z中寫下了這一點,但是它在ZF5E265E2607CB722582FEEB712582FEEB1B722582FE AS BINCT ATSB782FFE ATS BTEN26582FFE ATSB.BB720058FC721008FC721008FC721008FC721008。
我能做些什么來讓它表現得更好,或者以其他方式改進它? 謝謝!
Rust 代碼:
use num_integer::Roots;
fn main() {
let v = 984067;
// let v = 87539319;
for i in 1..=v {
ramanujan(i)
}
}
fn ramanujan(m: i32) {
let maxcube = m.cbrt();
let mut res1 = 0;
let mut res2 = 0;
let mut _res3 = 0;
let mut _res4 = 0;
for i in 1..=maxcube {
for j in 1..=maxcube {
if i * i * i + j * j * j == m {
res1 = i;
res2 = j;
break;
}
}
}
for k in 1..=maxcube {
for l in 1..=maxcube {
if k == res1 || k == res2 || l == res1 || l == res2 {
continue;
}
if k * k * k + l * l * l == m {
_res3 = k;
_res4 = l;
break;
}
}
}
// if ((res1 * res1 * res1) + (res2 * res2 * res2) == m) && ((res3 * res3 * res3) + (res4 * res4 * res4) == m) {
// println!("{} is representable as the sums of two different sets of two cubes!\nThese values are {}, {}, and {}, {}.", m, res1, res2, res3, res4);
// }
}
Java代碼:
public class Ramun {
public static void main(String[] args) {
int v = 984067;
// int v = 87539319;
for (int i = 1; i <= v; i++) {
ramanujan(i);
}
}
public static void ramanujan(int m) {
int maxcube = (int) Math.round(Math.cbrt(m));
int res1 = 0, res2 = 0, res3 = 0, res4 = 0;
for (int i = 1; i <= maxcube; i++) {
for (int j = 1; j <= maxcube; j++) {
if (((i * i * i) + (j * j * j)) == m) {
res1 = i;
res2 = j;
break;
}
}
}
for (int k = 1; k <= maxcube; k++) {
for (int l = 1; l <= maxcube; l++) {
if (k == res1 || k == res2 || l == res1 || l == res2)
continue;
if (((k * k * k) + (l * l * l)) == m) {
res3 = k;
res4 = l;
break;
}
}
}
// if (((res1 * res1 * res1) + (res2 * res2 * res2) == m) && ((res3 * res3 * res3) + (res4 * res4 * res4) == m)) {
// System.out.printf("%d is representable as the sums of two different sets of two cubes!%nThese values are %d, %d, and %d, %d.%n", m, res1, res2, res3, res4);
// }
}
}
問題在於RangeInclusive
。 它可能很昂貴:
use num_integer::Roots;
fn main() {
let v = 984067;
for i in 1..=v {
ramanujan(i)
}
}
fn ramanujan(m: i32) {
let maxcube = m.cbrt() + 1; // we know it can't overflow
let mut res1 = 0;
let mut res2 = 0;
let mut res3 = 0;
let mut res4 = 0;
for i in 1..maxcube {
for j in 1..maxcube {
if i * i * i + j * j * j == m {
res1 = i;
res2 = j;
break;
}
}
}
for k in 1..maxcube {
for l in 1..maxcube {
if k == res1 || k == res2 || l == res1 || l == res2 {
continue;
}
if k * k * k + l * l * l == m {
res3 = k;
res4 = l;
break;
}
}
}
}
結果:
From: 0.01s user 0.00s system 0% cpu 17.993 total
To: 0.00s user 0.01s system 0% cpu 3.494 total
向#45222添加評論以引起對該問題的關注。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.