Hemos discutido el desenrollado de bucles . La idea es aumentar el rendimiento agrupando sentencias de bucle para que haya menos instrucciones de control de bucle e instrucciones de prueba de bucle.
C++
// CPP program to compare normal loops and
// loops with unrolling technique
#include <iostream>
#include <time.h>
using namespace std;
int main() {
// n is 8 lakhs
int n = 800000;
// t to note start time
clock_t t = clock();
// to store the sum
long long int sum = 0;
// Normal loop
for (int i = 1; i <= n; i++)
sum += i;
// to mark end time
t = clock() - t;
cout << "sum is: " << sum << endl;
cout << "time taken by normal loops:"
"(float)t / CLOCKS_PER_SEC << " seconds"
<< endl;
// to mark start time of unrolling
t = clock();
// Unrolling technique (assuming that
// n is a multiple of 8).
sum = 0;
for (int i = 1; i <= n; i += 8) {
sum += i sum += (i + 1);
sum += (i + 2);
sum += (i + 3);
sum += (i + 4);
sum += (i + 5);
sum += (i + 6);
sum += (i + 7);
}
// to mark the end of loop
t = clock() - t;
cout << "Sum is: " << sum << endl;
cout << "Time taken by unrolling: "
"(float)t / CLOCKS_PER_SEC << " seconds";
return 0;
}
Java
// Java program to compare
// normal loops and loops
// with unrolling technique
class GFG
{
public static void main(String[] args)
{
// n is 8 lakhs
int n = 800000;
// t to note start time
double t = (double)System.nanoTime();
// to store the sum
long sum = 0;
// Normal loop
for (int i = 1; i <= n; i++)
sum += i;
// to mark end time
t = (double)System.nanoTime() - t;
System.out.println("sum is: "+
Double.toString(sum));
System.out.println("time taken by normal loops:" +
Double.toString(t / Math.pow(10.0, 9.0)));
// to mark start time
// of unrolling
t = (double)System.nanoTime();
// Unrolling technique
// (assuming that n is
// a multiple of 8).
sum = 0;
for (int i = 1; i <= n; i += 8)
{
sum += i ;
sum += (i + 1);
sum += (i + 2);
sum += (i + 3);
sum += (i + 4);
sum += (i + 5);
sum += (i + 6);
sum += (i + 7);
}
// to mark the end of loop
t = (double)System.nanoTime() - t;
System.out.println("sum is: " +
Double.toString(sum));
System.out.println("time taken by normal loops:" +
Double.toString(t / Math.pow(10.0, 9.0)));
}
}
// This code is contributed
// by Harshit Saini
Python3
# Python program to compare
# normal loops and loops
# with unrolling technique
from timeit import default_timer as clock
if __name__ == "__main__":
# n is 8 lakhs
n = 800000;
#t to note start time
t = clock()
# to store the sum
sum = 0
# Normal loop
for i in range(1, n + 1):
sum += i
# to mark end time
t = clock() - t
print("sum is: " + str(sum))
print("time taken by normal " +
"loops:" + str(t))
# to mark start
# time of unrolling
t = clock()
# Unrolling technique
# (assuming that n is
# a multiple of 8).
sum = 0
for i in range(1, n + 1, 8):
sum += i
sum += (i + 1)
sum += (i + 2)
sum += (i + 3)
sum += (i + 4)
sum += (i + 5)
sum += (i + 6)
sum += (i + 7)
# to mark the
# end of loop
t = clock() - t
print("Sum is: " + str(sum))
print("Time taken by unrolling: " +
str(t))
# This code is contributed
# by Harshit Saini
C#
// C# program to compare
// normal loops and loops
// with unrolling technique
using System;
using System.Diagnostics;
class GFG
{
private static double nanoTime()
{
long nano = 10000L * Stopwatch.GetTimestamp();
nano /= TimeSpan.TicksPerMillisecond;
nano *= 100L;
return nano;
}
public static void Main(String[] args)
{
// n is 8 lakhs
int n = 800000;
// t to note start time
double t = nanoTime();
// to store the sum
long sum = 0;
// Normal loop
for (int i = 1; i <= n; i++)
sum += i;
// to mark end time
t = nanoTime() - t;
Console.WriteLine("sum is: "+ sum);
Console.WriteLine("time taken by normal loops:" +
(t / Math.Pow(10.0, 9.0)));
// to mark start time
// of unrolling
t = nanoTime();
// Unrolling technique
// (assuming that n is
// a multiple of 8).
sum = 0;
for (int i = 1; i <= n; i += 8)
{
sum += i ;
sum += (i + 1);
sum += (i + 2);
sum += (i + 3);
sum += (i + 4);
sum += (i + 5);
sum += (i + 6);
sum += (i + 7);
}
// to mark the end of loop
t = nanoTime() - t;
Console.WriteLine("sum is: " + (sum));
Console.WriteLine("time taken by normal loops:" +
(t / Math.Pow(10.0, 9.0)));
}
}
// This code is contributed by 29AjayKumar
Javascript
<script>
// javascript program to compare
// normal loops and loops
// with unrolling technique
// n is 8 lakhs
var n = 800000;
// t to note start time
var t = new Date();
// to store the sum
var sum = 0;
// Normal loop
for (let i = 1; i <= n; i++)
sum += i;
// to mark end time
t = new Date() - t;
document.write("sum is: " +(sum));
document.write("<br/>time taken by normal loops:" +
(t / Math.pow(10.0, 9.0)).toFixed(10));
// to mark start time
// of unrolling
t = new Date();
// Unrolling technique
// (assuming that n is
// a multiple of 8).
sum = 0;
for (i = 1; i <= n; i += 8) {
sum += i;
sum += (i + 1);
sum += (i + 2);
sum += (i + 3);
sum += (i + 4);
sum += (i + 5);
sum += (i + 6);
sum += (i + 7);
}
// to mark the end of loop
t = new Date() - t;
document.write("<br/>sum is: " + (sum));
document.write("<br/>time taken by normal loops:" + (t / Math.pow(10.0, 9.0)).toFixed(10));
// This code is contributed by Rajput-Ji
</script>
Producción:
Sum is: 320000400000 Time taken: 0.002645 seconds Sum is: 320000400000 Time taken: 0.001799 seconds
Consulte el desenrollado de bucles para comparar los bucles normales y el desenrollado de bucles.
Publicación traducida automáticamente
Artículo escrito por shubham_rana_77 y traducido por Barcelona Geeks. The original can be accessed here. Licence: CCBY-SA