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  1. Commons Math
  2. MATH-1305

Improve performance of nextBytes() method of BitsStreamGenerator and AbstractRandomGenerator

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    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 4.0, 3.5, 3.6
    • Fix Version/s: 3.6
    • Labels:
      None
    • Flags:
      Patch, Important
    • External issue ID:

      Description

      I propose to use this code in BitsStreamGenerator

      	@Override
      	public void nextBytes(byte[] bytes) {
      		int index = 0;
      
      		// multiple 4 part of length, i.e. length with two least significant bits unset
      		int max = bytes.length & 0x7ffffffc;
      
      		// start filling the byte array with tetrads of bytes
      		while (index < max) {
      			int random = next(32);
      			bytes[index++] = (byte) random;
      			bytes[index++] = (byte) (random >>> 8);
      			bytes[index++] = (byte) (random >>> 16);
      			bytes[index++] = (byte) (random >>> 24);
      		}
      
      		// fill the remains bytes
      		if (index < bytes.length) {
      			int random = next(32);
      			while (true) {
      				bytes[index++] = (byte) random;
      				if (index < bytes.length) {
      					random >>>= 8;
      				} else {
      					break;
      				}
      			}
      		}
      	}
      

      I also propose to use the same code but with nextInt() calls instead of next(32) in the AbstractRandomGenerator. This implementation improves performance and fixes inconsistency bugs in those two classes discussed in the MATH-1300. It is also quite simple and well commented.

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              • Assignee:
                Unassigned
                Reporter:
                rosti.bsd Rostislav Krasny
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                • Created:
                  Updated:
                  Resolved: