乘法矩阵 Java

Question

我在为这段代码乘以矩阵时遇到了一些问题，当我用计算工具手动计算时，我得到的结果与我的代码给出的结果完全不同。

代码：

public class mult1 {
  /**
   * @param args the command line arguments
   */
  public static void main(String[] args) {
    double[][] colaO = {{.9,0.05,0.05},{0.05,.9,0.05},{0.05,0.05,.9}};//orginal
    double[][] colaD = {{.9,0.05,0.05},{0.05,.9,0.05},{0.05,0.05,.9}};//copy
    double[][] colaC = {{.9,0.05,0.05},{0.05,.9,0.05},{0.05,0.05,.9}};//for algs
    mult1 test = new mult1();
    test.output(colaC);
    test.Alg1(colaO, colaD, colaC);
    test.output(colaC);
  }
  public void Alg1(double colaO[][], double colaD[][], double colaC[][]) {
    for (int i = 0; i < colaO.length; i++) {
      for (int j = 0; j < colaO.length; j++) {
        for (int k = 0; k < colaO.length; k++) {
          colaC[i][j] += colaO[i][k] * colaD[k][j];
        }
      }
    }
  }
  public void output(double colaC[][]) {
    for (int i = 0; i < colaC.length; i++) {
      for (int j = 0; j < colaC.length; j++) {
        System.out.printf("%.3f", colaC[i][j]);
        System.out.print(" ");
      }
      System.out.println();
    }
  }
}

结果：

 ---original-----
 0.900 0.050 0.050 
 0.050 0.900 0.050 
 0.050 0.050 0.900 
 ---what i'm getting------
 1.715 0.143 0.143 
 0.143 1.715 0.143 
 0.143 0.143 1.715 
 ---should be-----
 0.815 0.092 0.092
 0.092 0.815 0.092
 0.092 0.092 0.815

我不太明白我在哪里弄乱了等式

Answer 1

嗯，我要做的第一件事是 0 初始化 colaC，因为您在其条目上使用 +=。你现在的做法无法得到正确的结果。

Answer 2

double[][] colaC = {{.9,0.05,0.05},{0.05,.9,0.05},{0.05,0.05,.9}};//for algs

应该是

double[][] colaC = {{0,0,0},{0,0,0},{0,0,0}};//for algs

乘法矩阵 Java

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