Fast Prime Sieve (Python Implementation)












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A modified version of the prime sieve. I actually doubt it could be implemented any faster, but I might be wrong:



from math import sqrt

def sieve(n):
"""
* A fast implementation of the prime sieve algorithm. Finds all prime numbers up to a given upper bound.

* Params:
* n: The upper bound.
* Return:
* A list of all prime numbers in [0, n].
* Implementation:
* Implements the sieve of Erasthotenes with a few optimisations for speed.
* We only delete multiples of numbers up to `int(sqrt(n))`. This suffices to find all prime numbers.
* We manipulate a list of boolean values, indexed by the number itself with the values denoting its primality. This is much faster than deleting elements in the list.
"""
if n < 2: return
prime = [True]*(n + 1) #Initialise the list.
rt = int(sqrt(n))+1
for x in range(2, rt): #We only need to seive multiples of numbers <= to `n`.
if prime[x]:
for c in range(x*x, n + 1, x): prime[c] = False
return [idx for idx, p in enumerate(prime) if p][2:]








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    $begingroup$


    A modified version of the prime sieve. I actually doubt it could be implemented any faster, but I might be wrong:



    from math import sqrt

    def sieve(n):
    """
    * A fast implementation of the prime sieve algorithm. Finds all prime numbers up to a given upper bound.

    * Params:
    * n: The upper bound.
    * Return:
    * A list of all prime numbers in [0, n].
    * Implementation:
    * Implements the sieve of Erasthotenes with a few optimisations for speed.
    * We only delete multiples of numbers up to `int(sqrt(n))`. This suffices to find all prime numbers.
    * We manipulate a list of boolean values, indexed by the number itself with the values denoting its primality. This is much faster than deleting elements in the list.
    """
    if n < 2: return
    prime = [True]*(n + 1) #Initialise the list.
    rt = int(sqrt(n))+1
    for x in range(2, rt): #We only need to seive multiples of numbers <= to `n`.
    if prime[x]:
    for c in range(x*x, n + 1, x): prime[c] = False
    return [idx for idx, p in enumerate(prime) if p][2:]








    share









    $endgroup$















      0












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      0





      $begingroup$


      A modified version of the prime sieve. I actually doubt it could be implemented any faster, but I might be wrong:



      from math import sqrt

      def sieve(n):
      """
      * A fast implementation of the prime sieve algorithm. Finds all prime numbers up to a given upper bound.

      * Params:
      * n: The upper bound.
      * Return:
      * A list of all prime numbers in [0, n].
      * Implementation:
      * Implements the sieve of Erasthotenes with a few optimisations for speed.
      * We only delete multiples of numbers up to `int(sqrt(n))`. This suffices to find all prime numbers.
      * We manipulate a list of boolean values, indexed by the number itself with the values denoting its primality. This is much faster than deleting elements in the list.
      """
      if n < 2: return
      prime = [True]*(n + 1) #Initialise the list.
      rt = int(sqrt(n))+1
      for x in range(2, rt): #We only need to seive multiples of numbers <= to `n`.
      if prime[x]:
      for c in range(x*x, n + 1, x): prime[c] = False
      return [idx for idx, p in enumerate(prime) if p][2:]








      share









      $endgroup$




      A modified version of the prime sieve. I actually doubt it could be implemented any faster, but I might be wrong:



      from math import sqrt

      def sieve(n):
      """
      * A fast implementation of the prime sieve algorithm. Finds all prime numbers up to a given upper bound.

      * Params:
      * n: The upper bound.
      * Return:
      * A list of all prime numbers in [0, n].
      * Implementation:
      * Implements the sieve of Erasthotenes with a few optimisations for speed.
      * We only delete multiples of numbers up to `int(sqrt(n))`. This suffices to find all prime numbers.
      * We manipulate a list of boolean values, indexed by the number itself with the values denoting its primality. This is much faster than deleting elements in the list.
      """
      if n < 2: return
      prime = [True]*(n + 1) #Initialise the list.
      rt = int(sqrt(n))+1
      for x in range(2, rt): #We only need to seive multiples of numbers <= to `n`.
      if prime[x]:
      for c in range(x*x, n + 1, x): prime[c] = False
      return [idx for idx, p in enumerate(prime) if p][2:]






      performance beginner algorithm primes sieve-of-eratosthenes





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      asked 7 mins ago









      Tobi AlafinTobi Alafin

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