仅在特定维度上求和 [英] sum only on certain dimension

问题描述

我有一个Fortran 90array(矩阵)，例如:

I have a Fortran 90array (matrix) like:

REAL(8),DIMENSION(Xmax, Ymax, Zmax, Xmax, Ymax, Zmax) :: Mat

我以这种方式阅读矩阵:

I read through my matrix in this way:

    DO X1=1,Xmax
      Do Y1=1,Ymax
        DO Z1=1,Zmax 

           DO Xv=1,Xmax
              Do Yv=1,Ymax
                DO Zv=1,Zmax 

                   Mat(X1, Y1, Z1, Xv, Yv, Zv)


           END DO
         END DO
        END DO
      END DO
    END DO
  END DO

我想创建一个新的矩阵NewMat(仅尺寸(Xmax，Ymax，Zmax))，该矩阵将为每个(Xv, Yv, Zv)包含初始矩阵中所有(X1, Y1, Z1)的总和.

I would like to create a new matrix NewMat (dimension(Xmax, Ymax, Zmax) only) which will contain for each (Xv, Yv, Zv) the sum of all respectively (X1, Y1, Z1) from my initial matrix.

我的问题是:我需要迭代求和吗?还是有一种使用某些功能的方法?有什么会更有效的?

My question is: Do I need to iterate to sum? Or is there a way to use some function? what would be more efficient?

推荐答案

您几乎肯定会在寻找内在的sum函数，该函数可用于将数组从列n减少到列n-1.所以表达

You're almost certainly looking for the intrinsic sum function which can be used to reduce an array (by addition) from rank n to rank n-1. So the expression

 sum(mat, dim=6)

将展平" mat的第六维.我不能完全确定我确切了解您要做什么，但是要完成任务

will 'flatten' the 6th dimension of mat. I'm not entirely sure that I understand exactly what you are trying to do, but the assignment

 newmat = sum(sum(sum(mat, dim=6), dim=5), dim=4)

可以满足您的需求.我还没有在这台机器上安装Fortran，如果有的话，我可能不愿意设置6级数组来对其进行测试.因此，如果不是您想要的东西，那么直到您得到它为止.

might satisfy your needs. I haven't got Fortran on this machine, and if I had I'd probably balk at setting up a rank-6 array to test it. So, if it isn't quite what you want fiddle around until you get it..

这可能不会比嵌套循环快得多，并且很难理解，但看起来确实是由了解现代Fortran数组操作的人编写的.

This probably isn't any faster than nesting loops, and it's arguably harder to read, but it does look like it was written by someone who understands modern Fortran's array operations.

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