Sets all values in an array to a specific value faster than a loop

Description

Demo Code


using System;//from   w  w  w. java2s .  c  o m

public class Main{
        /** Sets all values in an array to a specific value faster than a loop.
      * Only faster for large arrays. Slower for small ones.
      * Tests indicate it becomes faster somewhere when the length of the array grows above around 100.
      * For large arrays this can be magnitudes faster. Up to 40 times faster has been measured.
      * 
      * \note Only works on primitive value types such as int, long, float, etc.
      * 
      * \param array the array to fill
      * \param value the value to fill the array with
      * \param byteSize size in bytes of every element in the array. e.g 4 bytes for an int, or 8 bytes for a long.
      * \param totalSize all indices in the range [0, totalSize-1] will be set
      * 
      * It can be efficiently got using the sizeof built-in function.
      * 
\code
//Set all values to 8 in the array
int[] arr = new int[20000];
Pathfinding.Util.Memory.MemSet<int> (arr, 8, sizeof(int));
\endcode
      * \see System.Buffer.BlockCopy
      */
      public static void MemSet<T> (T[] array, T value, int totalSize, int byteSize) where T : struct {
         if (array == null) {
            throw new ArgumentNullException("array");
         }
         
         int block = 32, index = 0;
         int length = Math.Min(block, totalSize);
         
         //Fill the initial array
         while (index < length) {
            array[index] = value;
            index++;
         }
         
         length = totalSize;
         while (index < length) {
            Buffer.BlockCopy(array, 0, array, index*byteSize, Math.Min(block, totalSize-index)*byteSize);
            index += block;
            block *= 2;
         }
      }
        /** Sets all values in an array to a specific value faster than a loop.
      * Only faster for large arrays. Slower for small ones.
      * Tests indicate it becomes faster somewhere when the length of the array grows above around 100.
      * For large arrays this can be magnitudes faster. Up to 40 times faster has been measured.
      * 
      * \note Only works on primitive value types such as int, long, float, etc.
      * 
      * \param array the array to fill
      * \param value the value to fill the array with
      * \param byteSize size in bytes of every element in the array. e.g 4 bytes for an int, or 8 bytes for a long.
      * It can be efficiently got using the sizeof built-in function.
      * 
\code
//Set all values to 8 in the array
int[] arr = new int[20000];
Pathfinding.Util.Memory.MemSet<int> (arr, 8, sizeof(int));
\endcode
      * \see System.Buffer.BlockCopy
      */
      public static void MemSet<T> (T[] array, T value, int byteSize) where T : struct {
         if (array == null) {
            throw new ArgumentNullException("array");
         }
         
         int block = 32, index = 0;
         int length = Math.Min(block, array.Length);
         
         //Fill the initial array
         while (index < length) {
            array[index] = value;
            index++;
         }
         
         length = array.Length;
         while (index < length) {
            Buffer.BlockCopy(array, 0, array, index*byteSize, Math.Min(block, length-index)*byteSize);
            index += block;
            block *= 2;
         }
      }
        /** Sets all values in an array to a specific value faster than a loop.
      * Only faster for large arrays. Slower for small ones.
      * Tests indicate it becomes faster somewhere when the length of the array grows above around 100.
      * For large arrays this can be magnitudes faster. Up to 40 times faster has been measured.
      * 
      * \see System.Buffer.BlockCopy
      */
      public static void MemSet(byte[] array, byte value) {
         if (array == null) {
            throw new ArgumentNullException("array");
         }
         
         int block = 32, index = 0;
         int length = Math.Min(block, array.Length);
         
         //Fill the initial array
         while (index < length) {
            array[index++] = value;
         }
         
         length = array.Length;
         while (index < length) {
            Buffer.BlockCopy(array, 0, array, index, Math.Min(block, length-index));
            index += block;
            block *= 2;
         }
      }
}
Sets all values in an array to a specific value faster than a loop - CSharp System

Description

Demo Code

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