最快的方法数2维数组复制到一个一维数组（C语言） [英] Fastest way to copy several 2-dimensional arrays into one 1-dimensional array (in C)

问题描述

欲复制的3维阵列的多个2维子阵列（如数组1 [n]的[行] [COLS]，...，array4 [n]的[行] [COLS]），这是动态分配（但固定长度），成一维阵列（例如阵列[4 *行* COLS]），它是静态分配，在C作为将有许多行和列（例如，10000行和500列），我想知道其中的以下三种可能性将是最快的：

I want to copy several 2-dimensional subarrays of 3-dimensional arrays (e.g. array1[n][rows][cols], ..., array4[n][rows][cols]), which are dynamically allocated (but with fixed length), into a 1-dimensional array (e.g. array[4*rows*cols]), which is statically allocated, in C. As there will be many rows and columns (e.g. 10000 rows and 500 columns), I was wondering which of the following three possibilities will be the fastest:

    for(i=0;i<rows;i++){
      for(j=0;j<cols;j++){
        array[i*cols+j]=array1[2][i][j];
      }
    }
    ...
    for(i=0;i<rows;i++){
      for(j=0;j<cols;j++){
        array[3*rows*cols+i*cols+j]=array4[2][i][j];
        }
    }

或

    for(i=0;i<rows;i++){
      for(j=0;j<cols;j++){
        array[i*cols+j]=array1[2][i][j];
      }
      ...
      for(j=0;j<cols;j++){
        array[3*rows*cols+i*cols+j]=array4[2][i][j];
      }
    }

或

    for(i=0;i<rows;i++){
      for(j=0;j<cols;j++){
        array[i*cols+j]=array1[2][i][j];
        ...
        array[3*rows*cols+i*cols+j]=array4[2][i][j];
      }
    }

还是有甚至在C（不是C ++）？

Or is there even a faster way of performing this task in C (not C++)?

非常感谢！ （我想应该已经是一个类似的问题，但遗憾的是没有找到正是我一直在寻找的。所以，我很抱歉，如果我错过了这样一个问题。）

Thanks a lot! (I thought there should be a similar question already, but unfortunately did not find exactly what I was looking for. So, I am sorry if I missed such a question.)

编辑：
之所以希望做，这是以下：具有通过MPI来传达存储在这些2维（子）阵列的信息。这样，客户端将执行上述操作和主（种）的其他方式轮（即1维 - > 2维）。那么，有没有甚至更好的方式来做到这一点的整体？

The reason for wanting to do this is the following: The information stored in those 2-dimensional (sub-)arrays has to be communicated via MPI. So, clients will do the above and the master (kind of) the other way round (i.e. 1-dimensional -> 2-dimensional). So, is there even a better way to do this overall?

推荐答案

假设线性阵列和相同的尺寸（这将作废我的答案）：

Assuming linear arrays and the same dimensions (which would invalidate my answer):

这

for(i=0;i<rows;i++) {
  for(j=0;j<cols;j++) {
    array[i*cols+j]=array1[2][i][j];
  }
}

可以通过以下方式代替：

could be replace by:

memcpy(array, array1[2], sizeof(array1[2]));

因此​​这一个：

Accordingly this one:

for(i=0;i<rows;i++) {
  for(j=0;j<cols;j++) {
    array[3*rows*cols+i*cols+j]=array4[2][i][j];
  }
}

将是：

memcpy(array + 3*cols*rows, array4[2], sizeof(array4[2]));

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