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Home  >  Article  >  Web Front-end  >  How to solve JavaScript heap out of memory problem to find prime numbers?

How to solve JavaScript heap out of memory problem to find prime numbers?

王林
王林forward
2023-08-27 18:01:021256browse

How to solve JavaScript heap out of memory problem to find prime numbers?

As the "Out of Heap" error message indicates, this error occurs when any JavaScript code takes up more memory than allocated. When we run any JavaScript program, the computer allocates specific memory for the JavaScript program.

When we run code in JavaScript or any programming language, the computer creates a process and allocates a fixed amount of memory. When a program needs more memory space, it throws an error such as out of heap memory. For example, if we create an array of size 1020 and try to initialize each array index with a certain value, the heap will run out of memory and throw an error.

In this tutorial, we will learn how to solve JavaScript heap memory exhaustion problem when finding prime factors of a very large set of values.

Users can follow the following examples to visualize heap memory overflow errors.

Example (visualization error)

In the example below, we create the getPrimeFactors() function, which returns the prime factors of any number. When we pass a small number (close to 103) it works perfectly, but when we pass a large number (close to 109) as argument to find the prime factor, it gives an error and the browser window turns black.

In this example, since we use two nested loops to traverse the array, a memory error will occur and the time complexity of the program becomes O(N2), which is faster than the allocated More memory. 

<html>
<body>
   <h2>Visualizing the <i>Process out of memory</i> while finding all prime factors of a number in JavaScript </h2>
</body>
<script>
   try {
      function getPrimeFactors(num) {
         var factor = []; 
         let primes = [];
         for (let m = 2; m <= num; m++) {
            if (!factor[m]) {
               primes.push(m);
               for (let n = m << 1; n <= num; n += m) {
                  factor[n] = true;
               }
            }
         }
         return primes;
      }
      getPrimeFactors(1212121212323)
   } catch (err) {
      console.log(err.message)
   }
</script>
</html>

In the above example output, the user can observe a heap memory overflow error. To get rid of this problem, we need to optimize the time and space complexity of the code.

Below, we will optimize the time complexity of the code in Example 1 to find all unique prime factors of a given number.

grammar

Users can write optimization code according to the following syntax to find the unique prime factor of a given value. 

for (let m = 2; m * m <= value; m++) {
   if (value % m === 0) {
      
      // store factor to array
      while (value % m === 0) {
         value /= m;
      }
   }
}
if (value > 2) {
   
   // store factor to array
}

In the above syntax, we use a for loop to iterate until m*m is less than the value. This means we iterate until the square root of the value is greater than m.

Steps

Step 1 − Use a for loop to iterate until the square root of the value is greater than m, where m is the initialization variable of the for loop.

Step 2 - In the for loop, if the value is divisible by m, then it means that m is a prime factor of the value and stores it in the factors array.

Step 3 − After this, divide the value by m and use a while loop to divide by m multiple times if it can be divided multiple times. Here, we need to store unique prime factors, so we only store the value of m once in the array.

Step 4 - Once all iterations of the for loop are complete, check if the value is greater than 2. If it is, it means that the value is the largest prime factor and stores it in the array.

Example (resolving errors)

The following example uses an array to store prime factors. Furthermore, we have implemented the above algorithm to find prime factors.

Users can try to find the unique prime factor of a large value (such as 1020) and see if the code can output without any errors. 

<html>
<body>
   <h2>Solving the <i> Process out of memory </i> while finding all prime factors of a number in JavaScript</h2>
   <div id = "output"> </div>
</body>
<script>
   let output = document.getElementById('output');
   function getPrimeFactors(value) {
      let initial = value;
      var factors = [];
      for (let m = 2; m * m <= value; m++) {

         // if the value is divisible by m, it is a prime factor
         if (value % m === 0) {
            factors.push(m);

            // divide value by m until it is divisible
            while (value % m === 0) {
               value /= m;
            }
         }
      }

      // push largest prime factor at last
      if (value > 2) {
         factors.push(value); 
      }
      output.innerHTML += "The prime factors of " + initial + " are : " + factors + "<br/>";
   }
   getPrimeFactors(100000000002);
   getPrimeFactors(65416841658746141122);
</script>
</html>
The Chinese translation of

Example

is:

Example

In the following example, we use set to store prime factors instead of using arrays, because we need to obtain unique prime factors. Additionally, we used a for-of loop to print all the prime factors stored in the set. 

<html>
<body>
   <h2>Solving the <i> Process out of memory </i> while finding all prime factors of a number in JavaScript</h2>
   <div id = "output"> </div>
</body>
<script>
   let output = document.getElementById('output');
   function getPrimeFactors(value) {
      let initial = value;
      var factors = new Set();
      for (let m = 2; m * m <= value; m++) {
         if (value % m === 0) {
            factors.add(m);
            while (value % m === 0) {
               value /= m;
            }
         }
      }
      if (value > 2) {
         factors.add(value);
      }
      output.innerHTML += "The prime factors of " + initial + " are : <br/>";

      // print values of a set
      for (let fac of factors) {
         output.innerHTML += fac + "<br/>";
      }
   }
   getPrimeFactors(44352747207453165);
</script>
</html>

We learned to resolve heap overflow errors when finding prime factors of a number. Whenever we encounter errors like heap overflow, we need to optimize our code just like we have done in this tutorial.

The above is the detailed content of How to solve JavaScript heap out of memory problem to find prime numbers?. For more information, please follow other related articles on the PHP Chinese website!

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