Program for Picard’s iterative method | Computational Mathematics

Last Updated : 10 Feb, 2023

The Picard’s method is an iterative method and is primarily used for approximating solutions to differential equations. This method of solving a differential equation approximately is one of successive approximation; that is, it is an iterative method in which the numerical results become more and more accurate, the more times it is used. The Picard’s iterative method gives a sequence of approximations Y1(x), Y2(x), …Yk(x) to the solution of differential equations such that the nth approximation is obtained from one or more previous approximations. The Picard’s iterative series is relatively easy to implement and the solutions obtained through this numerical analysis are generally power series. Picard’s iteration method formula:

Picard’s iteration formula.

Steps involved:

Step 1: An approximate value of y (taken, at first, to be a constant) is substituted into the right hand side of the differential equation: dy/dx= f(x, y).
Step 2: The equation is then integrated with respect to x giving y in terms of x as a second approximation, into which given numerical values are substituted and the result rounded off to an assigned number of decimal places or significant figures.
Step 3: The iterative process is continued until two consecutive numerical solutions are the same when rounded off to the required number of decimal places.

Picard’s iteration example: Given that: and that y = 0 when x = 0, determine the value of y when x = 0.3, correct to four places of decimals. Solution: We may proceed as follows: where x0 = 0. Hence: where y0 = 0. which becomes:

First Iteration: We do not know y in terms of x yet, so we replace y by the constant value y0 in the function to be integrated. The result of the first iteration is thus given, at x = 0.3, by:
Second Iteration: Now, we use: Therefore, which gives: The result of the second iteration is thus given by: at x=0.3.
Third Iteration: Now we use: Therefore, which gives: The result of the third iteration is thus given by: at x = 0.3.
Hence, y = 0.0451, correct upto four decimal places, at x = 0.3.

Program for Picard’s iterative method:

C++

#include <cmath>
#include <iomanip>
#include <iostream>
using namespace std;
 
// required macros defined below:
double Y1(double x) { return (1 + (x) + pow(x, 2) / 2); }
double Y2(double x)
{
    return (1 + (x) + pow(x, 2) / 2 + pow(x, 3) / 3
            + pow(x, 4) / 8);
}
double Y3(double x)
{
    return 1 + (x) + pow(x, 2) / 2 + pow(x, 3) / 3
           + pow(x, 4) / 8 + pow(x, 5) / 15
           + pow(x, 6) / 48;
}
 
int main()
{
    double start_value = 0, end_value = 3,
           allowed_error = 0.4, temp;
    double y1[30];
    double y2[30];
    double y3[30];
    int count;
 
    for (temp = start_value, count = 0; temp <= end_value;
         temp = temp + allowed_error, count++) {
        y1[count] = Y1(temp);
        y2[count] = Y2(temp);
        y3[count] = Y3(temp);
    }
 
    cout << "\nX\n";
    for (temp = start_value; temp <= end_value;
         temp = temp + allowed_error) {
        cout << fixed << setprecision(4) << temp << " ";
    }
 
    cout << "\n\nY(1)\n";
    for (temp = start_value, count = 0; temp <= end_value;
         temp = temp + allowed_error, count++) {
        cout << fixed << setprecision(4) << y1[count]
             << " ";
    }
 
    cout << "\n\nY(2)\n";
    for (temp = start_value, count = 0; temp <= end_value;
         temp = temp + allowed_error, count++) {
        cout << fixed << setprecision(4) << y2[count]
             << " ";
    }
 
    cout << "\n\nY(3)\n";
    for (temp = start_value, count = 0; temp <= end_value;
         temp = temp + allowed_error, count++) {
        cout << fixed << setprecision(4) << y3[count]
             << " ";
    }
    return 0;
}
 
// This code is contributed by abn95knd1.

C

// C program for Picard's iterative method
   
#include <math.h>
#include <stdio.h>
   
// required macros defined below:
#define Y1(x) (1 + (x) + pow(x, 2) / 2)
#define Y2(x) (1 + (x) + pow(x, 2) / 2 + pow(x, 3) / 3 + pow(x, 4) / 8)
#define Y3(x) (1 + (x) + pow(x, 2) / 2 + pow(x, 3) / 3 + pow(x, 4) / 8 + pow(x, 5) / 15 + pow(x, 6) / 48)
   
int main()
{
    double start_value = 0, end_value = 3,
           allowed_error = 0.4, temp;
    double y1[30], y2[30], y3[30];
    int count;
   
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
   
        y1[count] = Y1(temp);
        y2[count] = Y2(temp);
        y3[count] = Y3(temp);
    }
   
    printf("\nX\n");
    for (temp = start_value;
         temp <= end_value;
         temp = temp + allowed_error) {
   
        // considering all values
        // upto 4 decimal places.
        printf("%.4lf ", temp);
    }
   
    printf("\n\nY(1)\n");
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
   
        printf("%.4lf ", y1[count]);
    }
   
    printf("\n\nY(2)\n");
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
   
        printf("%.4lf ", y2[count]);
    }
   
    printf("\n\nY(3)\n");
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
   
        printf("%.4lf ", y3[count]);
    }
    return 0;
}

Java

// Java program for Picard's iterative method
import java.util.*;
class GFG {
 
  // required macros defined below:
  static double Y1(double x)
  {
    return (1 + (x) + Math.pow(x, 2) / 2);
  }
  static double Y2(double x)
  {
    return (1 + (x) + Math.pow(x, 2) / 2
            + Math.pow(x, 3) / 3 + Math.pow(x, 4) / 8);
  }
  static double Y3(double x)
  {
    return 1 + (x) + Math.pow(x, 2) / 2
      + Math.pow(x, 3) / 3 + Math.pow(x, 4) / 8
      + Math.pow(x, 5) / 15 + Math.pow(x, 6) / 48;
  }
 
  public static void main(String[] args)
  {
    double start_value = 0, end_value = 3,
    allowed_error = 0.4, temp;
    double y1[] = new double[30];
    double y2[] = new double[30];
    double y3[] = new double[30];
    int count;
 
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
 
      y1[count] = Y1(temp);
      y2[count] = Y2(temp);
      y3[count] = Y3(temp);
    }
 
    System.out.printf("\nX\n");
    for (temp = start_value; temp <= end_value;
         temp = temp + allowed_error) {
 
      // considering all values
      // upto 4 decimal places.
      System.out.printf("%.4f ", temp);
    }
 
    System.out.printf("\n\nY(1)\n");
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
 
      System.out.printf("%.4f ", y1[count]);
    }
 
    System.out.printf("\n\nY(2)\n");
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
 
      System.out.printf("%.4f ", y2[count]);
    }
 
    System.out.printf("\n\nY(3)\n");
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
 
      System.out.printf("%.4f ", y3[count]);
    }
  }
}
 
// This code is contributed by phasing17

Python3

# Python3 program for Picard's iterative method
 
import math
   
# required macros defined below:
def Y1(x): 
     return (1 + (x) + pow(x, 2) / 2) 
def Y2(x):
     return (1 + (x) + pow(x, 2) / 2 + pow(x, 3) / 3 + pow(x, 4) / 8) 
def Y3(x) :
     return (1 + (x) + pow(x, 2) / 2 + pow(x, 3) / 3 + pow(x, 4) / 8 + pow(x, 5) / 15 + pow(x, 6) / 48)
   
start_value = 0
end_value = 3
allowed_error = 0.4
y1 = [0 for _ in range(30)]
y2 = [0 for _ in range(30)]
y3 = [0 for _ in range(30)]
 
temp = start_value
count = 0
while temp <= end_value:
 
    y1[count] = Y1(temp);
    y2[count] = Y2(temp);
    y3[count] = Y3(temp);
     
    temp = temp + allowed_error
    count += 1
   
print("\nX");
temp = start_value
while temp <= end_value:
     
    # considering all values
    # upto 4 decimal places.
    print(round(temp, 4), end = " ")
    temp = temp + allowed_error
         
print("\n\nY(1)");
temp = start_value
count = 0
while temp <= end_value:
    print(round(y1[count], 4), end = " ")
 
    temp = temp + allowed_error
    count += 1
   
print("\n\nY(2)");
temp = start_value
count = 0
while temp <= end_value:
    print(round(y2[count], 4), end = " ")
 
    temp = temp + allowed_error
    count += 1
 
print("\n\nY(3)");
temp = start_value
count = 0
while temp <= end_value:
    print(round(y3[count], 4), end = " ")
 
    temp = temp + allowed_error
    count += 1
     
 
# This code is contributed by phasing17

C#

// C# program for Picard's iterative method
 
using System;
using System.Collections.Generic;
 
class GFG {
 
    // required macros defined below:
    static double Y1(double x)
    {
        return (1 + (x) + Math.Pow(x, 2) / 2);
    }
    static double Y2(double x)
    {
        return (1 + (x) + Math.Pow(x, 2) / 2
                + Math.Pow(x, 3) / 3 + Math.Pow(x, 4) / 8);
    }
    static double Y3(double x)
    {
        return 1 + (x) + Math.Pow(x, 2) / 2
            + Math.Pow(x, 3) / 3 + Math.Pow(x, 4) / 8
            + Math.Pow(x, 5) / 15 + Math.Pow(x, 6) / 48;
    }
 
    public static void Main(string[] args)
    {
        double start_value = 0, end_value = 3,
               allowed_error = 0.4, temp;
        double[] y1 = new double[30];
        double[] y2 = new double[30];
        double[] y3 = new double[30];
        int count;
 
        for (temp = start_value, count = 0;
             temp <= end_value;
             temp = temp + allowed_error, count++) {
 
            y1[count] = Y1(temp);
            y2[count] = Y2(temp);
            y3[count] = Y3(temp);
        }
 
        Console.Write("\nX\n");
        for (temp = start_value; temp <= end_value;
             temp = temp + allowed_error) {
 
            // considering all values
            // upto 4 decimal places.
            Console.Write(Math.Round(temp, 4) + " ");
        }
 
        Console.Write("\n\nY(1)\n");
        for (temp = start_value, count = 0;
             temp <= end_value;
             temp = temp + allowed_error, count++) {
 
            Console.Write(y1[count] + " ");
        }
 
        Console.Write("\n\nY(2)\n");
        for (temp = start_value, count = 0;
             temp <= end_value;
             temp = temp + allowed_error, count++) {
 
            Console.Write(Math.Round(y2[count], 4) + " ");
        }
 
        Console.Write("\n\nY(3)\n");
        for (temp = start_value, count = 0;
             temp <= end_value;
             temp = temp + allowed_error, count++) {
 
            Console.Write(Math.Round(y3[count], 4) + " ");
        }
    }
}
 
// This code is contributed by phasing17

Javascript

// JavaScript program for Picard's iterative method
 
   
// required macros defined below:
function Y1(x) 
    { return (1 + (x) + Math.pow(x, 2) / 2) }
function Y2(x) 
    { return (1 + (x) + Math.pow(x, 2) / 2 + Math.pow(x, 3) / 3 + Math.pow(x, 4) / 8) }
function Y3(x) 
    { return (1 + (x) + Math.pow(x, 2) / 2 + Math.pow(x, 3) / 3 + Math.pow(x, 4) / 8 + Math.pow(x, 5) / 15 + Math.pow(x, 6) / 48)}
   
let start_value = 0, end_value = 3,
           allowed_error = 0.4, temp;
let y1 = new Array(30);
let y2 = new Array(30);
let y3 = new Array(30);
let count;
   
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
   
        y1[count] = Y1(temp);
        y2[count] = Y2(temp);
        y3[count] = Y3(temp);
    }
   
    console.log("\nX");
    for (temp = start_value;
         temp <= end_value;
         temp = temp + allowed_error) {
   
        // considering all values
        // upto 4 decimal places.
        console.log(temp.toFixed(4));
    }
   
    console.log("\n\nY(1)");
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
        console.log((y1[count]).toFixed(4));
    }
   
    console.log("\n\nY(2)");
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
         
        console.log((y2[count]).toFixed(4));
    }
   
    console.log("\n\nY(3)");
    for (temp = start_value, count = 0;
         temp <= end_value;
         temp = temp + allowed_error, count++) {
     
        console.log((y3[count]).toFixed(4));
    }
 
// This code is contributed by phasing17

Output:

X
0.0000 0.4000 0.8000 1.2000 1.6000 2.0000 2.4000 2.8000 

Y(1)
1.0000 1.4800 2.1200 2.9200 3.8800 5.0000 6.2800 7.7200 

Y(2)
1.0000 1.5045 2.3419 3.7552 6.0645 9.6667 15.0352 22.7205 

Y(3)
1.0000 1.5053 2.3692 3.9833 7.1131 13.1333 24.3249 44.2335

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