如何在Android Studio中覆盖/更新Jama矩阵而不会出现任何错误? [英] How to overwrite/update a Jama Matrix in Android Studio without any error?

问题描述

Jama矩阵在我的代码(矩阵计算类)中定义如下:

Jama Matrices are defined in my code (Matrix computation class) as follows:

private Matrix A;
private Matrix B;
private Matrix C;

矩阵A初始化如下:

A = new Matrix(2,2);
A.set(0,0,1.5);
A.set(0,1,0.0);
A.set(1,0,0.0);
A.set(1,1,1.5);

Matrix B是一个2 * 2矩阵，被初始化为一个单位矩阵，并被MainActivity类中大小相同的下一个矩阵每秒更新一次.

Matrix B is a 2*2 matrix, initialized as an identity matrix and is updated every second by the next matrix of the same size from the MainActivity class.

矩阵C的初始化和计算如下:

Matrix C is initialized and computed as follows:

 if(C!=null)
 C = A.plus(C.times(B));
 else {
 C = new Matrix(2,2);
 C.set(0,0,1);
 C.set(0,1,0.0);
 C.set(1,0,0.0);
 C.set(1,1,1);

在这里， MainActivity类每秒调用一次 Matrix计算类，并相应地更新矩阵B.但是，该代码仅在第一次迭代时运行良好，并在稍后抛出错误，如下所示:

Here, the Matrix computation class is called by the MainActivity class every second and matrix B is updated accordingly. However, the code runs well for only the first iteration and throws an error in later as follows:

java.lang.IllegalArgumentException: Matrix inner dimensions must agree.

经过一番挖掘，我发现这是由于矩阵覆盖(矩阵B和C)引起的.我的代码中的矩阵不能为static或final.当矩阵不是静态的时候，有什么方法可以使用Jama矩阵吗?在Matrix Studio中，是否有替代Jama进行Matrix操作?

After some digging, I found that it is caused due to matrix overwriting (Matrix B and C). The matrices in my code cannot be static or final. Is there any way to use the Jama matrix when the matrices are not static? Are there any alternatives to Jama in the android studio for Matrix operation?

推荐答案

查看JAMA随附的源代码，在该位置抛出IllegalArgumentException:

Looking at the source code provided with JAMA, the IllegalArgumentException is thrown at that place:

   /** Linear algebraic matrix multiplication, A * B
   @param B    another matrix
   @return     Matrix product, A * B
   @exception  IllegalArgumentException Matrix inner dimensions must agree.
   */

   public Matrix times (Matrix B) {
      if (B.m != n) {
         throw new IllegalArgumentException("Matrix inner dimensions must agree.");
      }
      Matrix X = new Matrix(m,B.n);
      double[][] C = X.getArray();
      double[] Bcolj = new double[n];
      for (int j = 0; j < B.n; j++) {
         for (int k = 0; k < n; k++) {
            Bcolj[k] = B.A[k][j];
         }
         for (int i = 0; i < m; i++) {
            double[] Arowi = A[i];
            double s = 0;
            for (int k = 0; k < n; k++) {
               s += Arowi[k]*Bcolj[k];
            }
            C[i][j] = s;
         }
      }
      return X;
   }

因此，显然C.times(B)失败，这意味着C和B的尺寸不一致.从下面的行中我们还可以看到，C = new Matrix(2,2)确实具有2x2的大小，这意味着B必须具有错误的大小.

So appearently C.times(B) fails, which means that C and B dimensions do not agree. As we can also see from the line below, C = new Matrix(2,2) does have 2x2 size, which means that B must have a wrong size.

我不明白您所说的矩阵覆盖"是什么意思? C = A.plus(C.times(B))确实在内部分配了Matrix的新实例.这与static或final无关.

I do not understand what you mean with "matrix overwriting"? C = A.plus(C.times(B)) does allocate a new instance of Matrix internally. This has nothing to do with static or final.

请提供完整的最小示例.遗漏了很多部分，例如B初始化的地方.

Please provide a complete, minimal example. There are many parts missing, like the place where B is initialized.

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