kahansummation.java

来自「一个一元曲线多项式数值演示例子」· Java 代码 · 共 58 行

package numbercruncher.mathutils;

/**
 * Implement Kahan's Summation Algorithm for the float type.
 */
public class KahanSummation {
  /** the current running sum */
  private float sum;
  /** the current correction */
  private float correction;
  /** the current corrected added */
  private float correctedAddend;

  /**
   * Constructor.
   */
  public KahanSummation() {}

  /**
   * Return the current corrected value of the running sum.
   * @return the running sum's value
   */
  public float value() {
    return sum + correction;
  }

  /**
   * Return the corrected value of the current addend.
   * @return the corrected addend value
   */
  public float correctedAddend() {
    return correctedAddend;
  }

  /**
   * Add the value of an addend to the running sum.
   * @param the addend value
   */
  public void add(float addend) {
    // Correct the addend value and add it to the running sum.
    correctedAddend = addend + correction;
    float tempSum = sum + correctedAddend;

    // Compute the next correction and set the running sum.
    // The parentheses are necessary to compute the high-order
    // bits of the addend.
    correction = correctedAddend - (tempSum - sum);
    sum = tempSum;
  }

  /**
   * Clear the running sum and the correction.
   */
  public void clear() {
    sum = 0;
    correction = 0;
  }
}